For DSS clock domain to transition from idle to active state. It's necessary
to enable the optional clock DSS_FCLK before we enable the module using the
MODULEMODE bits in the clock domain's CM_DSS_DSS_CLKCTRL register.
This sequence was not followed correctly for the 'dss_hdmi' hwmod and it led
to DSS clock domain not getting out of idle when pm_runtime_get_sync() was
called for hdmi's platform device.
Since the clock domain failed to change it's state to active, the hwmod code
disables any clocks it had enabled before for this hwmod. This led to the clock
'dss_48mhz_clk' gettind disabled.
When hdmi's runtime_resume() op is called, the call to dss_runtime_get()
correctly enables the DSS clock domain this time. However, the clock
'dss_48mhz_clk' is needed for HDMI's PHY to function correctly. Since it was
disabled previously, the driver fails when it tries to enable HDMI's PHY.
Fix this for now by ensuring that dss_runtime_get() is called before we call
pm_runtime_get_sync() for hdmi's platform device. A correct fix for later would
be to modify the DSS related hwmod's mainclks, and also some changes in how
opt clocks are handled in the DSS driver.
This fixes the issue of HDMI not working when it's the default display. The
issue is not seen if any other display is already enabled as the first display
would have correctly enabled the DSS clockdomain.
Signed-off-by: Archit Taneja <redacted>
---
Changes in v2:
- Rewrite an unclear paragraph in the commit message
- Add comments mentioning that this is a hack
drivers/video/omap2/dss/hdmi.c | 24 +++++++++++++++++++++++-
1 files changed, 23 insertions(+), 1 deletions(-)
From: Tomi Valkeinen <hidden> Date: 2012-02-14 11:57:58
Hi,
On Fri, 2012-02-10 at 11:45 +0530, Archit Taneja wrote:
For DSS clock domain to transition from idle to active state. It's necessary
to enable the optional clock DSS_FCLK before we enable the module using the
MODULEMODE bits in the clock domain's CM_DSS_DSS_CLKCTRL register.
This sequence was not followed correctly for the 'dss_hdmi' hwmod and it led
to DSS clock domain not getting out of idle when pm_runtime_get_sync() was
called for hdmi's platform device.
Since the clock domain failed to change it's state to active, the hwmod code
disables any clocks it had enabled before for this hwmod. This led to the clock
'dss_48mhz_clk' gettind disabled.
When hdmi's runtime_resume() op is called, the call to dss_runtime_get()
correctly enables the DSS clock domain this time. However, the clock
'dss_48mhz_clk' is needed for HDMI's PHY to function correctly. Since it was
disabled previously, the driver fails when it tries to enable HDMI's PHY.
Fix this for now by ensuring that dss_runtime_get() is called before we call
pm_runtime_get_sync() for hdmi's platform device. A correct fix for later would
be to modify the DSS related hwmod's mainclks, and also some changes in how
opt clocks are handled in the DSS driver.
This fixes the issue of HDMI not working when it's the default display. The
issue is not seen if any other display is already enabled as the first display
would have correctly enabled the DSS clockdomain.
I think this looks fine, it's shouldn't have any side effects and is
easy to remove later.
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
Tomi
Hi Tomi,
On 2/14/2012 12:57 PM, Tomi Valkeinen wrote:
Hi,
On Fri, 2012-02-10 at 11:45 +0530, Archit Taneja wrote:
quoted
For DSS clock domain to transition from idle to active state. It's necessary
to enable the optional clock DSS_FCLK before we enable the module using the
MODULEMODE bits in the clock domain's CM_DSS_DSS_CLKCTRL register.
This sequence was not followed correctly for the 'dss_hdmi' hwmod and it led
to DSS clock domain not getting out of idle when pm_runtime_get_sync() was
called for hdmi's platform device.
Since the clock domain failed to change it's state to active, the hwmod code
disables any clocks it had enabled before for this hwmod. This led to the clock
'dss_48mhz_clk' gettind disabled.
When hdmi's runtime_resume() op is called, the call to dss_runtime_get()
correctly enables the DSS clock domain this time. However, the clock
'dss_48mhz_clk' is needed for HDMI's PHY to function correctly. Since it was
disabled previously, the driver fails when it tries to enable HDMI's PHY.
Fix this for now by ensuring that dss_runtime_get() is called before we call
pm_runtime_get_sync() for hdmi's platform device. A correct fix for later would
be to modify the DSS related hwmod's mainclks, and also some changes in how
opt clocks are handled in the DSS driver.
This fixes the issue of HDMI not working when it's the default display. The
issue is not seen if any other display is already enabled as the first display
would have correctly enabled the DSS clockdomain.
I think this looks fine, it's shouldn't have any side effects and is
easy to remove later.
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before any
of the child are used.
Implementing that with hwmod is not the right approach since is will
require to add some more complex OMAP custom stuff in the hwmod fmwk
whereas the LDM is already able to handle that.
The whole point is that going to device tree, we will have to change the
responsibility of hwmod to make it focus mainly on OMAP PRCM stuff and
let the device handles the IRQ/DMA/REG/CLKS resources since it is the
correct place to do that.
Regards,
Benoit
From: Tomi Valkeinen <hidden> Date: 2012-02-14 13:15:11
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
Hi Tomi,
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having dss_core as
the parent of other dss modules doesn't really fix that in any way.
Tomi
From: Tomi Valkeinen <hidden> Date: 2012-02-14 13:33:24
On Tue, 2012-02-14 at 19:00 +0530, Archit Taneja wrote:
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
Hmm, are you sure? Not that I checked the code, but isn't MODULEMODE
mapped to a dss clock (was it "dss_clk")?. And so, the clock's refcount
should keep the MODULEMODE enabled/disabled?
Tomi
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
Archit
On Tuesday 14 February 2012 07:03 PM, Tomi Valkeinen wrote:
On Tue, 2012-02-14 at 19:00 +0530, Archit Taneja wrote:
quoted
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
Hmm, are you sure? Not that I checked the code, but isn't MODULEMODE
mapped to a dss clock (was it "dss_clk")?. And so, the clock's refcount
should keep the MODULEMODE enabled/disabled?
Yes, that's how we are currently dealing with it and making things work.
We are forced to represent MODULEMODE as a clock. I forgot to mention
that in the last mail :)
However, other modules don't do this. modulemode control is taken care
by hwmod by itself. We just have to fill the hwmod field
'.prcm.omap4.modulemode' and get done with it. If we try this approach,
we get into the trouble I mentioned before.
We represent MODULEMODE as dss_fck, and make this the l3 slave clock for
all DSS hwmods. This way, we ensure that it gets enabled, and we get a
usecount associated to it. We shouldn't stick to this approach because:
- It isn't exactly correct. MODULEMODE isn't a clock, and others don't
do it.
- DSS requires a particular sequence of disabling clocks to go into
lower power states, and with the current approach, this doesn't happen.
So, DSS doesn't idle, and that's the whole purpose of this :)
Archit
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
And this is exactly what the pm_runtime will provide. The fmwk already
handles reference counting.
Moreover the dev->parent will increment the power.child_count and thus
ensure that the parent is always enabled if at least one child is active.
By initializing the dev->parent of each DSS modules to the dss_core, it
will ensure that the power dependency is managed properly.
Regards,
Benoit
On Tuesday 14 February 2012 07:03 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 19:00 +0530, Archit Taneja wrote:
quoted
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled
before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having
dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
Hmm, are you sure? Not that I checked the code, but isn't MODULEMODE
mapped to a dss clock (was it "dss_clk")?. And so, the clock's refcount
should keep the MODULEMODE enabled/disabled?
Yes, that's how we are currently dealing with it and making things work.
We are forced to represent MODULEMODE as a clock. I forgot to mention
that in the last mail :)
However, other modules don't do this. modulemode control is taken care
by hwmod by itself. We just have to fill the hwmod field
'.prcm.omap4.modulemode' and get done with it. If we try this approach,
we get into the trouble I mentioned before.
We represent MODULEMODE as dss_fck, and make this the l3 slave clock for
all DSS hwmods. This way, we ensure that it gets enabled, and we get a
usecount associated to it. We shouldn't stick to this approach because:
- It isn't exactly correct. MODULEMODE isn't a clock, and others don't
do it.
Yes, fully agree. This was done like that as a hack to avoid any
regression because at that time we were not sure if that dependency will
have to be handled by the hwmod fmwk or by the driver.
Now, I'm sure it should not be handled by the hwmod fmwk :-)
- DSS requires a particular sequence of disabling clocks to go into
lower power states, and with the current approach, this doesn't happen.
So, DSS doesn't idle, and that's the whole purpose of this :)
I'm just curious, what particular sequence is required?
Thanks,
Benoit
On Tue, Feb 14, 2012 at 9:32 PM, Cousson, Benoit [off-list ref] wrote:
On 2/14/2012 2:45 PM, Archit Taneja wrote:
quoted
On Tuesday 14 February 2012 07:03 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 19:00 +0530, Archit Taneja wrote:
quoted
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled
before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having
dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
Hmm, are you sure? Not that I checked the code, but isn't MODULEMODE
mapped to a dss clock (was it "dss_clk")?. And so, the clock's refcount
should keep the MODULEMODE enabled/disabled?
Yes, that's how we are currently dealing with it and making things work.
We are forced to represent MODULEMODE as a clock. I forgot to mention
that in the last mail :)
However, other modules don't do this. modulemode control is taken care
by hwmod by itself. We just have to fill the hwmod field
'.prcm.omap4.modulemode' and get done with it. If we try this approach,
we get into the trouble I mentioned before.
We represent MODULEMODE as dss_fck, and make this the l3 slave clock for
all DSS hwmods. This way, we ensure that it gets enabled, and we get a
usecount associated to it. We shouldn't stick to this approach because:
- It isn't exactly correct. MODULEMODE isn't a clock, and others don't
do it.
Yes, fully agree. This was done like that as a hack to avoid any regression
because at that time we were not sure if that dependency will have to be
handled by the hwmod fmwk or by the driver.
Now, I'm sure it should not be handled by the hwmod fmwk :-)
quoted
- DSS requires a particular sequence of disabling clocks to go into
lower power states, and with the current approach, this doesn't happen.
So, DSS doesn't idle, and that's the whole purpose of this :)
I'm just curious, what particular sequence is required?
IIRC, the main issue is the order in which functional clock and what
is so called
optional clock enabled ....
While enabling the module
1. Enable optional clock
2. Enabled module mode.
While disabling module
1. Disable module mode
2. Disable optional clock.
I think only above sequence work. Not following above in either
path leads to modules being stuck in transition.
Is that right Archit ?
On Tuesday 14 February 2012 10:29 PM, Shilimkar, Santosh wrote:
On Tue, Feb 14, 2012 at 9:32 PM, Cousson, Benoit[off-list ref] wrote:
quoted
On 2/14/2012 2:45 PM, Archit Taneja wrote:
quoted
On Tuesday 14 February 2012 07:03 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 19:00 +0530, Archit Taneja wrote:
quoted
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled
before any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having
dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
Hmm, are you sure? Not that I checked the code, but isn't MODULEMODE
mapped to a dss clock (was it "dss_clk")?. And so, the clock's refcount
should keep the MODULEMODE enabled/disabled?
Yes, that's how we are currently dealing with it and making things work.
We are forced to represent MODULEMODE as a clock. I forgot to mention
that in the last mail :)
However, other modules don't do this. modulemode control is taken care
by hwmod by itself. We just have to fill the hwmod field
'.prcm.omap4.modulemode' and get done with it. If we try this approach,
we get into the trouble I mentioned before.
We represent MODULEMODE as dss_fck, and make this the l3 slave clock for
all DSS hwmods. This way, we ensure that it gets enabled, and we get a
usecount associated to it. We shouldn't stick to this approach because:
- It isn't exactly correct. MODULEMODE isn't a clock, and others don't
do it.
Yes, fully agree. This was done like that as a hack to avoid any regression
because at that time we were not sure if that dependency will have to be
handled by the hwmod fmwk or by the driver.
Now, I'm sure it should not be handled by the hwmod fmwk :-)
quoted
- DSS requires a particular sequence of disabling clocks to go into
lower power states, and with the current approach, this doesn't happen.
So, DSS doesn't idle, and that's the whole purpose of this :)
I'm just curious, what particular sequence is required?
IIRC, the main issue is the order in which functional clock and what
is so called
optional clock enabled ....
While enabling the module
1. Enable optional clock
2. Enabled module mode.
While disabling module
1. Disable module mode
2. Disable optional clock.
I think only above sequence work. Not following above in either
path leads to modules being stuck in transition.
Is that right Archit ?
Yes. Also, this transition failure happens when DSS clock domain is set
to hardware supervised wakeup(HWAUTO).
The opt clock which requires this ordering with module mode is DSS_FCLK
by default. However, if some other clock (like DSI PLL, sourced by
SYS_CLK) is the source for DISPC_FCLK, then that clock is the one which
needs to be ordered with module mode.
Archit
--
To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tuesday 14 February 2012 09:11 PM, Cousson, Benoit wrote:
On 2/14/2012 2:30 PM, Archit Taneja wrote:
quoted
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before
any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
And this is exactly what the pm_runtime will provide. The fmwk already
handles reference counting.
Moreover the dev->parent will increment the power.child_count and thus
ensure that the parent is always enabled if at least one child is active.
By initializing the dev->parent of each DSS modules to the dss_core, it
will ensure that the power dependency is managed properly.
Yes, a parent/child relation will ensure the required dependencies. It
sounds good!
How do we take care of things in the meanwhile? With the current way of
representing modulemode as a slave clock, the disabling sequence gets
messed up. In arch/arm/mach-omap2/omap_hwmod.c:
static int _disable_clocks(struct omap_hwmod *oh)
{
...
disable mainclk;
disable slave clocks;
...
}
For DSS, mainclk is the DSS_FCLK opt clock, and slave clock is
modulemode bits. We need the opposite sequence to happen here to cleanly
disable DSS.
Any suggestions?
Thanks,
Archit
On Tuesday 14 February 2012 09:11 PM, Cousson, Benoit wrote:
quoted
On 2/14/2012 2:30 PM, Archit Taneja wrote:
quoted
Hi,
On Tuesday 14 February 2012 06:45 PM, Tomi Valkeinen wrote:
quoted
On Tue, 2012-02-14 at 13:58 +0100, Cousson, Benoit wrote:
quoted
Hi Tomi,
quoted
quoted
Benoit, do you think we'll get the MODULEMODE mess cleaned up in the
hwmod/clk framework at some point, and the drivers could do without
these kinds of hacks? =)
The best way to fix that for my point of view is to go to device tree
or/and to consider the DSS as the parent of all the DSS modules.
pm_runtime will then always ensure that the parent is enabled before
any
of the child are used.
Ah, right. Sounds fine to me.
But is that a proper "fix"? Are we sure the MODULEMODE will then always
be handled correctly? Isn't the core problem still there, it just
doesn't happen with the setup anymore?
I mean, if we have these special requirements regarding MODULEMODE, and
the code doesn't really know about it, would it get broken easily with
restructuring/changes?
And no, I don't have any clear idea why/how it would break, but I have
just gotten the impression that the MODULEMODE is not handled quite
properly (and so we have these current problems), and having
dss_core as
the parent of other dss modules doesn't really fix that in any way.
I agree with that.
In the current approach, we have multiple platform devices for DSS, and
all of them belong to the same clock domain, and the clock domain has
just one MODULEMODE bit field.
When shutting off a platform device(by calling pm_runtime_put()), hwmod
enables/disables MODULEMODE without taking into mind that other active
platform devices may still need it. So, for example, if we have 2
platform devices, say dss and dispc, and we have code like:
dispc_foo()
{
pm_runtime_get(dispc_pdev);
...
...
pm_runtime_put(dispc_pdev);
}
dss_foo()
{
pm_runtime_get(dss_pdev);
...
...
dispc_foo(); /* MODULEMODE off after this */
...
...
pm_runtime_put(dss_pdev);
}
This will lead to the situation of one platform device disabling
MODULEMODE even though other platform devices need it.
This may not be resolved in device tree either. We would need to have
some use count mechanism for these bits, or attach MODULEMODE only to
one platform device, and don't give others control to enable/disable it.
And this is exactly what the pm_runtime will provide. The fmwk already
handles reference counting.
Moreover the dev->parent will increment the power.child_count and thus
ensure that the parent is always enabled if at least one child is active.
By initializing the dev->parent of each DSS modules to the dss_core, it
will ensure that the power dependency is managed properly.
Yes, a parent/child relation will ensure the required dependencies. It
sounds good!
How do we take care of things in the meanwhile? With the current way of
representing modulemode as a slave clock, the disabling sequence gets
messed up. In arch/arm/mach-omap2/omap_hwmod.c:
static int _disable_clocks(struct omap_hwmod *oh)
{
...
disable mainclk;
disable slave clocks;
...
}
For DSS, mainclk is the DSS_FCLK opt clock, and slave clock is
modulemode bits. We need the opposite sequence to happen here to cleanly
disable DSS.
Yes, but as you pointed out the current clocks mapping in the DSS is a
hack that should not be done like that in theory.
As soon as the devices can handle the dependency, we will be able to fix
the clock mapping in the hwmod data and handle properly the module mode
only from the dss_core hwmod only.
But I think you have to change the driver first, otherwise it will break
the DSS. We did that hack previously because it was the only way to
enable the DSS properly, knowing that disabling it with that method will
be impossible.
I think that changing the device creation to change the dev->parent
should be pretty straightforward.
Regards,
Benoit
From: Tomi Valkeinen <hidden> Date: 2012-02-15 12:51:57
On Wed, 2012-02-15 at 13:35 +0100, Cousson, Benoit wrote:
I think that changing the device creation to change the dev->parent
should be pretty straightforward.
That's not possible with the current kernel, right?
We are now using omap_device_build() (in arch/arm/mach-omap2/display.c)
to build the dss devices. Looking at the omap_device.c, the parent will
always forcibly set to omap_device_parent. It'd be nice to be able to
construct the device child-parent relationship the same way with both DT
and non-DT cases.
Or can I create only the dss_core with omap_device_build(), and create
the rest normally with platform device functions, and make dss_core the
parent of the rest? But are the hwmods then handled correctly?
Tomi
+ Kevin
On 2/15/2012 1:51 PM, Tomi Valkeinen wrote:
On Wed, 2012-02-15 at 13:35 +0100, Cousson, Benoit wrote:
quoted
I think that changing the device creation to change the dev->parent
should be pretty straightforward.
That's not possible with the current kernel, right?
We are now using omap_device_build() (in arch/arm/mach-omap2/display.c)
to build the dss devices. Looking at the omap_device.c, the parent will
always forcibly set to omap_device_parent. It'd be nice to be able to
construct the device child-parent relationship the same way with both DT
and non-DT cases.
I guess this should not be needed anymore since now the whole PM runtime
stuff is handled using pm_domain.
int omap_device_register(struct platform_device *pdev)
{
pr_debug("omap_device: %s: registering\n", pdev->name);
pdev->dev.parent = &omap_device_parent;
pdev->dev.pm_domain = &omap_device_pm_domain;
return platform_device_add(pdev);
}
Kevin,
Do we still need to set the dev.parent to omap_device_parent?
I guess the default &platform_bus parent is good enough and potentially
the DSS children should be able to overwrite that.
Or can I create only the dss_core with omap_device_build(), and create
the rest normally with platform device functions, and make dss_core the
parent of the rest? But are the hwmods then handled correctly?
You can, the only issue if you create a regular platform device is that
you will miss the automatic pm_runtime support along with the hwmod
device creation mechanism + clock / PM.
I think we can add an extra parameter to allow changing the omap_device
parent during omap_device_build.
Regards,
Benoit
From: Kevin Hilman <hidden> Date: 2012-02-15 19:59:19
"Cousson, Benoit" [off-list ref] writes:
+ Kevin
On 2/15/2012 1:51 PM, Tomi Valkeinen wrote:
quoted
On Wed, 2012-02-15 at 13:35 +0100, Cousson, Benoit wrote:
quoted
I think that changing the device creation to change the dev->parent
should be pretty straightforward.
That's not possible with the current kernel, right?
We are now using omap_device_build() (in arch/arm/mach-omap2/display.c)
to build the dss devices. Looking at the omap_device.c, the parent will
always forcibly set to omap_device_parent. It'd be nice to be able to
construct the device child-parent relationship the same way with both DT
and non-DT cases.
I guess this should not be needed anymore since now the whole PM
runtime stuff is handled using pm_domain.
int omap_device_register(struct platform_device *pdev)
{
pr_debug("omap_device: %s: registering\n", pdev->name);
pdev->dev.parent = &omap_device_parent;
pdev->dev.pm_domain = &omap_device_pm_domain;
return platform_device_add(pdev);
}
Kevin,
Do we still need to set the dev.parent to omap_device_parent?
Nope.
I guess the default &platform_bus parent is good enough and
potentially the DSS children should be able to overwrite that.
Yes, now that we use PM domains, we don't need it. I just sent a patch
to remove omap_device_parent.
Kevin
quoted
Or can I create only the dss_core with omap_device_build(), and create
the rest normally with platform device functions, and make dss_core the
parent of the rest? But are the hwmods then handled correctly?
You can, the only issue if you create a regular platform device is
that you will miss the automatic pm_runtime support along with the
hwmod device creation mechanism + clock / PM.
I think we can add an extra parameter to allow changing the
omap_device parent during omap_device_build.
From: Tomi Valkeinen <hidden> Date: 2012-02-16 08:22:16
On Wed, 2012-02-15 at 11:59 -0800, Kevin Hilman wrote:
"Cousson, Benoit" [off-list ref] writes:
quoted
Kevin,
Do we still need to set the dev.parent to omap_device_parent?
Nope.
quoted
I guess the default &platform_bus parent is good enough and
potentially the DSS children should be able to overwrite that.
Yes, now that we use PM domains, we don't need it. I just sent a patch
to remove omap_device_parent.
But it's still not possible to create a custom parent-child hierarchy
with omap_devices. Or can I change the parent of a platform_device after
it has been created? (doesn't sound very clean even if I can)
Tomi
On Wed, 2012-02-15 at 11:59 -0800, Kevin Hilman wrote:
quoted
"Cousson, Benoit"[off-list ref] writes:
quoted
quoted
Kevin,
Do we still need to set the dev.parent to omap_device_parent?
Nope.
quoted
I guess the default&platform_bus parent is good enough and
potentially the DSS children should be able to overwrite that.
Yes, now that we use PM domains, we don't need it. I just sent a patch
to remove omap_device_parent.
But it's still not possible to create a custom parent-child hierarchy
with omap_devices. Or can I change the parent of a platform_device after
it has been created? (doesn't sound very clean even if I can)
Nope, it has to be done before platform_device_add.
Thanks to Ohad patch [1] that Tony has just resent, you can use the
internal omap_device API and thus will be able to change the parent
before the registration.
Benoit
[1] ARM: OMAP: omap_device: Expose omap_device_{alloc, delete, register}