On 7/17/19 5:25 PM, Sowjanya Komatineni wrote:

On 7/17/19 4:44 PM, Dmitry Osipenko wrote:

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18.07.2019 2:36, Sowjanya Komatineni пишет:

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On 7/17/19 3:48 PM, Dmitry Osipenko wrote:

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18.07.2019 0:57, Sowjanya Komatineni пишет:

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On 7/17/19 2:51 PM, Sowjanya Komatineni wrote:

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On 7/17/19 2:30 PM, Dmitry Osipenko wrote:

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17.07.2019 23:11, Sowjanya Komatineni пишет:

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On 7/17/19 1:01 PM, Sowjanya Komatineni wrote:

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On 7/17/19 12:43 PM, Dmitry Osipenko wrote:

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17.07.2019 21:54, Sowjanya Komatineni пишет:

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On 7/17/19 11:51 AM, Sowjanya Komatineni wrote:

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On 7/17/19 11:32 AM, Dmitry Osipenko wrote:

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17.07.2019 20:29, Sowjanya Komatineni пишет:

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On 7/17/19 8:17 AM, Dmitry Osipenko wrote:

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17.07.2019 9:36, Sowjanya Komatineni пишет:

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On 7/16/19 11:33 PM, Dmitry Osipenko wrote:

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В Tue, 16 Jul 2019 22:55:52 -0700
Sowjanya Komatineni [off-list ref] пишет:

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On 7/16/19 10:42 PM, Dmitry Osipenko wrote:

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В Tue, 16 Jul 2019 22:25:25 -0700
Sowjanya Komatineni [off-list ref] пишет:

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On 7/16/19 9:11 PM, Dmitry Osipenko wrote:

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В Tue, 16 Jul 2019 19:35:49 -0700
Sowjanya Komatineni [off-list ref] пишет:

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On 7/16/19 7:18 PM, Sowjanya Komatineni wrote:

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On 7/16/19 3:06 PM, Sowjanya Komatineni wrote:

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On 7/16/19 3:00 PM, Dmitry Osipenko wrote:

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17.07.2019 0:35, Sowjanya Komatineni пишет:

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On 7/16/19 2:21 PM, Dmitry Osipenko wrote:

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17.07.2019 0:12, Sowjanya Komatineni пишет:

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On 7/16/19 1:47 PM, Dmitry Osipenko wrote:

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16.07.2019 22:26, Sowjanya Komatineni пишет:

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On 7/16/19 11:43 AM, Dmitry Osipenko wrote:

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16.07.2019 21:30, Sowjanya Komatineni 
пишет:

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On 7/16/19 11:25 AM, Dmitry Osipenko 
wrote:

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16.07.2019 21:19, Sowjanya Komatineni 
пишет:

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On 7/16/19 9:50 AM, Sowjanya Komatineni
wrote:

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On 7/16/19 8:00 AM, Dmitry Osipenko 
wrote:

quoted

16.07.2019 11:06, Peter De Schrijver
пишет:

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On Tue, Jul 16, 2019 at 03:24:26PM
+0800,
Joseph
Lo wrote:

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OK, Will add to CPUFreq driver...

quoted

The other thing that also need
attention is
that T124 CPUFreq
driver
implicitly relies on DFLL driver
to be
probed
first, which is
icky.

Should I add check for successful
dfll clk
register explicitly in
CPUFreq driver probe and defer till
dfll
clk
registers?

Probably you should use the "device
links".
See
[1][2] for the
example.

[1]
https://elixir.bootlin.com/linux/v5.2.1/source/drivers/gpu/drm/tegra/dc.c#L2383 














[2]
https://www.kernel.org/doc/html/latest/driver-api/device_link.html 










Return EPROBE_DEFER instead of 
EINVAL if
device_link_add() fails.
And
use of_find_device_by_node() to get 
the
DFLL's
device, see [3].

[3]
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/devfreq/tegra20-devfreq.c#n100 

Will go thru and add...

Looks like I initially confused this case
with
getting
orphaned clock.
I'm now seeing that the DFLL driver
registers the
clock and then
clk_get(dfll) should be returning
EPROBE_DEFER
until
DFLL driver is
probed, hence everything should be fine
as-is and
there is no real
need
for the 'device link'. Sorry for the
confusion!

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Sorry, I didn't follow the mail
thread. Just
regarding the DFLL
part.

As you know it, the DFLL clock is 
one
of the
CPU
clock sources and
integrated with DVFS control logic
with the
regulator. We will not
switch
CPU to other clock sources once we
switched to
DFLL. Because the
CPU has
been regulated by the DFLL HW 
with the
DVFS
table
(CVB or OPP
table
you see
in the driver.). We shouldn't 
reparent
it to
other sources with
unknew
freq/volt pair. That's not
guaranteed to
work. We
allow switching to
open-loop mode but different 
sources.

Okay, then the CPUFreq driver will
have to
enforce
DFLL freq to
PLLP's
rate before switching to PLLP in 
order to
have a
proper CPU voltage.

PLLP freq is safe to work for any CPU
voltage.
So no
need to enforce
DFLL freq to PLLP rate before changing
CCLK_G
source
to PLLP during
suspend

Sorry, please ignore my above comment.
During
suspend, need to change
CCLK_G source to PLLP when dfll is in
closed
loop
mode first and
then
dfll need to be set to open loop.

Okay.

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And I don't exactly understand 
why we
need to
switch to PLLP in
CPU
idle
driver. Just keep it on CL-DVFS mode
all the
time.

In SC7 entry, the dfll suspend 
function
moves it
the open-loop
mode. That's
all. The sc7-entryfirmware will 
handle
the rest
of the sequence to
turn off
the CPU power.

In SC7 resume, the warmboot code 
will
handle
the
sequence to
turn on
regulator and power up the CPU
cluster. And
leave
it on PLL_P.
After
resuming to the kernel, we re-init
DFLL,
restore
the CPU clock
policy (CPU
runs on DFLL open-loop mode) and 
then
moving to
close-loop mode.

The DFLL is re-inited after switching
CCLK to
DFLL
parent during of
the
early clocks-state restoring by CaR
driver.
Hence
instead of having
odd
hacks in the CaR driver, it is much
nicer to
have a
proper suspend-resume sequencing of 
the
device
drivers. In this case
CPUFreq
driver is the driver that enables DFLL
and
switches
CPU to that
clock
source, which means that this 
driver is
also
should
be responsible for
management of the DFLL's state 
during of
suspend/resume process. If
CPUFreq driver disables DFLL during
suspend
and
re-enables it
during
resume, then looks like the CaR driver
hacks
around
DFLL are not
needed.

quoted

quoted

The DFLL part looks good to me. BTW,
change the
patch subject to
"Add
suspend-resume support" seems more
appropriate to
me.

To clarify this, the sequences for 
DFLL
use
are as
follows (assuming
all
required DFLL hw configuration has 
been
done)

Switch to DFLL:
0) Save current parent and frequency
1) Program DFLL to open loop mode
2) Enable DFLL
3) Change cclk_g parent to DFLL
For OVR regulator:
4) Change PWM output pin from
tristate to
output
5) Enable DFLL PWM output
For I2C regulator:
4) Enable DFLL I2C output
6) Program DFLL to closed loop mode

Switch away from DFLL:
0) Change cclk_g parent to PLLP so
the CPU
frequency is ok for
any
vdd_cpu voltage
1) Program DFLL to open loop mode

I see during switch away from DFLL
(suspend),
cclk_g
parent is not
changed to PLLP before changing dfll to
open
loop
mode.

Will add this ...

The CPUFreq driver switches parent to 
PLLP
during
the
probe, similar
should be done on suspend.

I'm also wondering if it's always safe to
switch to
PLLP in the probe.
If CPU is running on a lower freq than
PLLP, then
some
other more
appropriate intermediate parent should be
selected.

CPU parents are PLL_X, PLL_P, and dfll. 
PLL_X
always
runs at higher
rate
so switching to PLL_P during CPUFreq probe
prior to
dfll clock enable
should be safe.

AFAIK, PLLX could run at ~200MHz. There is
also a
divided output of
PLLP
which CCLKG supports, the PLLP_OUT4.

Probably, realistically, CPU is always 
running
off a
fast PLLX during
boot, but I'm wondering what may happen on
KEXEC. I
guess ideally CPUFreq driver should also
have a
'shutdown' callback to teardown DFLL
on a reboot, but likely that there are 
other
clock-related problems as
well that may break KEXEC and thus it is 
not
very
important at the
moment.

[snip]

During bootup CPUG sources from PLL_X. By 
PLL_P
source
above I meant
PLL_P_OUT4.

As per clock policies, PLL_X is always used
for high
freq
like

quoted

800Mhz

and for low frequency it will be sourced 
from
PLLP.

Alright, then please don't forget to
pre-initialize
PLLP_OUT4 rate to a
reasonable value using 
tegra_clk_init_table or
assigned-clocks.

PLLP_OUT4 rate update is not needed as it is
safe to
run at
408Mhz because it is below fmax @ Vmin

So even 204MHz CVB entries are having the same
voltage as
408MHz, correct? It's not instantly obvious 
to me
from the
DFLL driver's code where the fmax @ Vmin is
defined,
I see
that there is the min_millivolts
and frequency entries starting from 204MHZ 
defined
per-table.

Yes at Vmin CPU Fmax is ~800Mhz. So anything 
below
that
will
work at Vmin voltage and PLLP max is 408Mhz.

Thank you for the clarification. It would be good
to have
that
commented
in the code as well.

OK, Will add...

Regarding, adding suspend/resume to CPUFreq, 
CPUFreq
suspend
happens very early even before disabling non-boot
CPUs and
also
need to export clock driver APIs to CPUFreq.

Was thinking of below way of implementing this...


Clock DFLL driver Suspend:

                 - Save CPU clock policy 
registers, and
Perform
dfll
suspend which sets in open loop mode

CPU Freq driver Suspend: does nothing


Clock DFLL driver Resume:

                 - Re-init DFLL, Set in 
Open-Loop mode,
restore
CPU
Clock policy registers which actually sets 
source to
DFLL
along
with other CPU Policy register restore.

CPU Freq driver Resume:

                 - do clk_prepare_enable which 
acutally
sets
DFLL in
Closed loop mode


Adding one more note: Switching CPU Clock to PLLP
is not
needed
as CPU CLock can be from dfll in open-loop mode as
DFLL
is not
disabled anywhere throught the suspend/resume path
and SC7
entry
FW and Warm boot code will switch CPU source to 
PLLP.

Since CPU resumes on PLLP, it will be cleaner to 
suspend
it on
PLLP as well. And besides, seems that currently
disabling
DFLL
clock will disable DFLL completely and then you'd
want to
re-init
the DFLL on resume any ways. So better to just 
disable
DFLL
completely on suspend, which should happen on
clk_disable(dfll).

Will switch to PLLP during CPUFreq suspend. With
decision of
using
clk_disable during suspend, its mandatory to switch to
PLLP as
DFLL
is completely disabled.

My earlier concern was on restoring CPU policy as we
can't do
that
from CPUFreq driver and need export from clock driver.

Clear now and will do CPU clock policy restore in 
after
dfll
re-init.

Why the policy can't be saved/restored by the CaR 
driver
as a
context of any other clock?

restoring cpu clock policy involves programming 
source and
super_cclkg_divider.

cclk_g is registered as clk_super_mux and it doesn't use
frac_div ops
to do save/restore its divider.

That can be changed of course and I guess it also could
be as
simple as
saving and restoring of two raw u32 values of the
policy/divider
registers.

quoted

Also, during clock context we cant restore cclk_g as 
cclk_g
source
will be dfll and dfll will not be resumed/re-initialized
by the
time
clk_super_mux save/restore happens.

we can't use save/restore context for dfll clk_ops 
because
dfllCPU_out parent to CCLK_G is first in the clock 
tree and
dfll_ref
and dfll_soc peripheral clocks are not restored by the
time dfll
restore happens. Also dfll peripheral clock enables need
to be
restored before dfll restore happens which involves
programming
dfll
controller for re-initialization.

So dfll resume/re-init is done in clk-tegra210 at end of
all
clocks
restore in V5 series but instead of in clk-tegra210
driver I
moved
now to dfll-fcpu driver pm_ops as all dfll dependencies
will be
restored thru clk_restore_context by then. This will 
be in
V6.

Since DFLL is now guaranteed to be disabled across CaR
suspend/resume
(hence it has nothing to do in regards to CCLK) and given
that
PLLs
state is restored before the rest of the clocks, I don't
see why
not to
implement CCLK save/restore in a generic fasion. CPU 
policy
wull be
restored to either PLLP or PLLX (if CPUFreq driver is
disabled).

CCLK_G save/restore should happen in clk_super_mux ops
save/context and
clk_super_mux save/restore happens very early as cclk_g is
first
in the
clock tree and save/restore traverses through the tree
top-bottom
order.

If CCLK_G is restored before the PLLs, then just change the
clocks
order
such that it won't happen.

I dont think we can change clocks order for CCLK_G.

During bootup, cclk_g is registered after all pll's and
peripheral
clocks which is the way we wanted, So cclk_g will be the 
first
one in
the clk list as clk_register adds new clock first in the 
list.

When clk_save_context and clk_restore_context APIs iterates
over the
list, cclk_g is the first

Looking at clk_core_restore_context(), I see that it walks up
CLKs
list
from parent to children, hence I don't understand how it can
ever
happen
that CCLK will be restored before the parent. The clocks
registration
order doesn't matter at all in that case.

yes from parent to children and dfllCPU_out is the top in the
list and
its child is cclk_g.

the way clocks are registered is the order I see in the clock
list and
looking into clk_register API it adds new node first in the 
list.

cclkg_g & dfll register happens after all plls and peripheral
clocks as
it need ref, soc and peripheral clocks to be enabled.

quoted

So they are the last to get registered and so becomes first in
the
list.

During save/restore context, it traverses thru this list and
first in
the list is dfllcpu_OUT (parent) and its child (cclk_g)

saving should not be an issue at all but we cant restore
cclk_g/dfll
in normal way thru clk_ops restore as plls and peripherals
restore
doesn't happen by that time.

I was referring to clk_restore_context where it iterates thru
root list
and for each core from the root list clk_core_restore does
restore of
parent and children.

dfllCPU_Out gets first in the list and its child is cclk_g

https://elixir.bootlin.com/linux/v5.2.1/source/drivers/clk/clk.c#L1105 

What list you're talking about? clk_summary? It shows current
*active*
clocks configuration, if you'll try to disable CPUFreq driver 
then
the
parent of CCLK_G should be PLLX. Similarly when CPU is
reparented to
PLLP on driver's suspend, then PLLP is the parent.

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DFLL enable thru CPUFreq resume happens after all
clk_restore_context
happens. So during clk_restore_context, dfll re-init 
doesnt
happen
and
doing cpu clock policy restore during super_mux clk_ops 
will
crash as
DFLL is not initialized and its clock is not enabled 
but CPU
clock
restore sets source to DFLL if we restore during
super_clk_mux

If CPU was suspended on PLLP, then it will be restored on
PLLP by
CaR. I
don't understand what DFLL has to do with the CCLK in that
case
during
the clocks restore.

My above comment is in reference to your request of doing
save/restore
for cclk_g in normal fashion thru save/restore context. 
Because
of the
clk order I mentioned above, we cclk_g will be the first 
one to
go thru
save/context.

During save_context of cclk_g, source can be from PLLX, 
dfll.

Issue will be when we do restore during 
clk_restore_context of
cclk_g as
by that time PLLX/dfll will not be restored.

Seems we already agreed that DFLL will be disabled by the
CPUFreq
driver
on suspend. Hence CCLK can't be from DFLL if CPU is
reparented to
PLLP
on CPUFreq driver's suspend, otherwise CPU keeps running 
from a
boot-state PLLX if CPUFreq driver is disabled.

Yes suspend should not be an issue but issue will be during
resume
where if we do cclk_g restore in normal way thru
clk_restore_context,
cclk_g restore happens very early as dfllCPU out is the first
one that
goes thru restore context and plls/peripherals are not 
resumed by
then.

CPU runs from PLLX if dfll clock enable fails during boot. So
when it
gets to suspend, we save CPU running clock source as either
PLLX or
DFLL and then we switch to PLLP.


On resume, CPU runs from PLLP by warm boot code and we need to
restore
back its source to the one it was using from saved source 
context
(which can be either PLLX or DFLL)

So PLLs & DFLL resume need to happen before CCLKG 
restore/resume.


With all above discussions, we do DFLL disable in CPUFreq
driver on
suspend and on CPUFreq resume we enable DFLL back and 
restore CPU
clock source it was using during suspend (which will be either
PLLX if
dfll enable fails during probe or it will be using DFLL).

During suspend CPU's parent shall be PLLP and not DFLL (note 
that
it is
disabled) after reparenting to PLLP by the CPUFreq driver.

CPU source context should be saved before switching to safe
source of
PLLP as on resume we need to restore back to source it was using
before we switch to safe source during suspend entry.

So saved context for CPU Source will be either dfll or PLLX

PLLP reparenting is only during suspend/entry to have it as safe
source
but actual CPU source it was running from before suspending is 
either
dfll/pllx which should be the one to be restored on CPUFreq 
resume.
Resume happens with CPU running from PLLP till it gets to the
point of
restoring its original source (dfll or pllx)

CaR should restore CPU to PLLP or PLLX, while CPUFreq driver 
restores
CPU to DFLL. Please see more comments below.

quoted

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So i was trying to say dfll/cclk_g restore can't be done in
normal way
thru clk_ops save/restore context

Let's see what happens if CPUFreq is active:

1. CPUFreq driver probe happens
       2. CPU is reparented to PLLP
       3. DFLL inited
       4. CPU is reparented to DFLL

5. CPUFreq driver suspend happens
       6. CPU is reparented to PLLP
       7. DFLL is disabled

8. Car suspend happens
       9. DFLL context saved
       10. PLLP/PLLX context saved
       11. CCLK context saved

12. Car resume happens
       13. DFLL context restored
       14. PLLP/PLLX context restored
       15. CCLK context restored

16. CPUFreq driver resume happens
       17. DFLL re-inited
       18. CPU is reparented to DFLL

Below is the order of sequence it should be based on the order of
clk
register.

My comments inline in this sequence.

1. CPUFreq driver probe happens
       2. CPU is reparented to PLLP
       3. DFLL inited
       4. CPU is reparented to DFLL


5. CPUFreq driver suspend happens
       6. Save CPU source which could be either dfll or pllx

Please see my next comment.

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       7. CPU is reparented to safe known source PLLP
       8. DFLL is disabled

8. Car suspend happens
       9. DFLL context saved (With DFLL disabled in CPUFreq 
suspend,
nothing to be saved here as last freq req will always be saved).
       10. CCLK context saved (CPU clock source will be saved in
CPUFreq
driver suspend which could be either dfll or pllx)

That I don't understand. The CPU's clock source state should be
saved at
the moment of the CaR's suspending (i.e. CCLK policy will be set to
PLLP
or PLLX) and then CCLK state should be also restored by the CaR in
step 14.

CPU clock to be saved and restored should be the source used 
before we
switch it to safe PLLP for suspend/resume operation.

This original source could be either PLLX or DFLL which it was using
before we disable DFLL during CPU Freq suspend.

If we save CPU clock source at moment of CAR suspending, it will be
PLLP as we switch to safe PLLP in CPUFreq driver suspend.

Infact, we dont need to restore CPU clock source to PLLP anywhere in
resume as it comes up with PLLP source from warm boot code itself.

You must always maintain proper suspend/resume encapsulation, 
otherwise
it's a total mess. It doesn't matter that CCLK is restored to PLLP 
even
that CPU is already running off PLLP after warmboot.

quoted

quoted

But we need to restore CPU source to original source it was using
before we switch to safe PLLP source for suspend operation. This
original source could be PLLX/DFLL and this should be re-stored in
CPUFreq resume as by this time PLLs and peripherals are restored and
dfll is re-initialized.

So saving actual CPU source before switching to intermediate safe 
PLLP
in CPUFreq driver and then restoring back during CPUFreq resume 
should
be good as CPUFreq resume happens right after all clocks (plls
restore, peripherals restore, dfll resume)>>

quoted

CPUFreq driver should only switch CPU to PLLP and disable DFLL on
suspend in step 5, that's it. On resume CPUFreq driver will restore
CPU
to DFLL in step 18.

Also I don't think we should hard-code to force CPU source to 
DFLL on
CPUFreq resume.

Reason is during CPU Probe when it tries to switch to dfll 
source, for
some reason if dfll enable fails it sets CPU to its original source
which will be PLLX.

No!

1. CPU voltage could be too low for PLLX
2. PLLX rate can't be changed without manual reparenting CPU to
intermediate clock
3. CPUFreq can't manually manage CPU voltage

DFLL-restoring failure is an extreme case. CPU must be kept on a safe
PLLP in that case and disable_cpufreq() must be invoked as well.

OK, PLLX option was also in my mind. So If we just consider sources as
DFLL or PLLP, then we can save source in CCLK save context and restore
in CCLK restore basically it will be PLLP.

Later during CPUFreq resume we can just switch to DFLL and if DFLL
enable fails we will keep source as PLLP. Yes will invoke
disable_cpufreq as well in case of dfll enable failure for some reason.

Sounds good!

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So CPU source could be either DFLL or PLLX in CPUFreq
tegra124_cpu_switch_to_dfll

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       11. PLLP/PLLX context saved
       12. Peripheral Clock saved

12. Car resume happens
       13. DFLL context restored : No DFLL context to be restored
and we
only need to reinitialize DFLL and re-initialize can't be done
here as
this is the 1st to get restored and PLL/Peripheral clocks are not
restored by this time. So we can't use clk_ops restore for DFLL

It looks to me that clk_core_restore_context() should just do
hlist_for_each_entry *_reverse*. Don't you think so?

Thought of that but this is in core driver and is used by other
non-tegra clock driver and not sure if that impacts for those.

The reverse ordering should be correct, I think it's just a 
shortcoming
of the CCF that need to be fixed. But will better to make a more
thorough research, asking Stephen and Michael for the clarification.

quoted

quoted

But with decision of switching CPUFreq with dfll clock 
enable/disable
during CPUFreq suspend/resume, we can re-init dfll during dfll-fcpu
driver resume and we don't need CCLK save/restore.

Actually CPUFreq driver should implement suspend/resume regardless of
CaR ability to restore DFLL or whatever, simply to properly handle
possible clock restoring failure on resume as we just found out.

quoted

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quoted

the way of all clocks order is good except cclk_g which has 
dependency
on multiple clocks.

CCLK_G has a single parent at a time. What "multiple clocks" you're
talking about? Please explain.

dependencies I am referring are dfll_ref, dfll_soc, and DVFS peripheral
clocks which need to be restored prior to DFLL reinit.

Okay, but that shouldn't be a problem if clock dependencies are set up
properly.

quoted

quoted

quoted

reverse list order during restore might not work as all other 
clocks are
in proper order no with any ref clocks for plls getting restored 
prior
to their clients

Why? The ref clocks should be registered first and be the roots for 
PLLs
and the rest. If it's not currently the case, then this need to be
fixed. You need to ensure that each clock is modeled properly. If some
child clock really depends on multiple parents, then the parents 
need to
in the correct order or CCF need to be taught about such
multi-dependencies.

If some required feature is missed, then you have to implement it
properly and for all, that's how things are done in upstream. 
Sometimes
it's quite a lot of extra work that everyone are benefiting from in
the end.

[snip]

Yes, we should register ref/parents before their clients.

cclk_g clk is registered last after all pll and peripheral clocks are
registers during clock init.

dfllCPU_out clk is registered later during dfll-fcpu driver probe and
gets added to the clock list.

Probably the issue seems to be not linking dfll_ref and dfll_soc
dependencies for dfllCPU_out thru clock list.

clk-dfll driver during dfll_init_clks gets ref_clk and soc_clk 
reference
thru DT.

Please try to fix all missing dependencies and orderings.

Peter,

dfllCPU_OUT is the first one to go thru restore when 
clk_restore_context traverses thru the list.

dfllCPU_OUT has dependency on DFLL_ref and DFLL_SOC but this 
dependency is unknown to clock-tree.

We can add DFLL_REF and DFLL_SOC as parents to dfllCPU_OUT during 
register so dfllCPU_OUT save/restore happens after their parents are 
restored.

But DFLL needs both of these to be restored before DFLLCPU_Out and as 
DFLL_SOC restore always happens after the REF, thinking to add 
DFLL_SOC as parent to dfllCPU_OUT so save/restore follows after their 
dependencies.

Please comment.

Did quick try and I see by adding dfll-soc as parent to dfllCPU_OUT, its 
in proper order after all its dependencies.

Can now add dfll save/restore to do dfll reinit during restore..