On Thu, Dec 20, 2012 at 04:54:38PM -0600, Jon Hunter wrote:

On 12/20/2012 01:51 PM, Pratik Patel wrote:

quoted

On Thu, Dec 20, 2012 at 11:46:13AM -0600, Jon Hunter wrote:

quoted

On 12/19/2012 03:24 PM, Pratik Patel wrote:

[snip]

quoted

Currently we use the CoreSight virtual bus to conveniently list
sysfs configuration attributes for all the registered CoreSight
devices.

For eg:
/sys/bus/coresight/devices/coresight-etm0/<attribute>
/sys/bus/coresight/devices/coresight-etm1/<attribute>
/sys/bus/coresight/devices/coresight-stm/<attribute>
/sys/bus/coresight/devices/coresight-tmc-etf/<attribute>
...
...

Some of the attributes are based on device type (i.e. source,
link or sink) so they will exist for all devices of that type
while some are device specific.

Maybe I am misunderstanding the question but are you suggesting
to register CoreSight devices to the AMBA bus instead of the
CoreSight core layer code?

Yes exactly.

quoted

Will Deacon mentioned earlier that AMBA framework can be changed
to accomodate devices with a different class but I am more
concerned with losing some of the stuff that the core layer code
does (eg. coresight_register, coresight_enable, coresight_disable
in coresight.c) if we register CoreSight drivers to the AMBA bus
without letting the core layer know about the device connections.

I may be missing something, but couldn't you keep all the
register/enable/disable stuff but just register the device with the amba
bus? Obviously some changes would need to be made.

Ok, so are you referring to making CoreSight devices register
with AMBA bus instead of platform bus keeping everything else
intact?

Yes exactly. However, please note I am not saying that we should do
this, and I asking what direction does the community want us to take
here? Platform bus or AMBA bus?

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quoted

Personally, I don't have strong feeling either way, but we have ETM/ETB
drivers using AMBA today and so I am hoping we can come to agreement on
this going forward.

Russell, Will, what are your thoughts?

Otherwise, looking at the code, I like what you have implemented. I
still need to look closer, but I am struggling to figure out how a
coresight device such as the cross-trigger-interface fits with this
model. This model appears to be geared towards coresight devices used
for traces purposes and are either source, links or sinks. The
cross-trigger-interface is not a source or a sink. However, although you
it could be considered as a link (routing events), it is not really, as
it may not link to other coresight sinks/source.

In my case, I have PMU-IRQ --> CTI --> GIC. So a non-coresight source
and sink. In away the CTI looks more like a 2nd-level interrupt
controller than anything else. Hence, another type of coresight device
may be needed in addition to source, links and sinks. Or link is
extended in some way to connect to non-coresight sources/sinks.

Let me know if you have any thoughts.

I had left the "None" type for miscellaneous stuff but I agree it
should be a separate type - maybe "debug".

Having said that I like the CTI driver you have uploaded. Need to
look at it in more detail. Since CTI connections can vary between
chip to chip, we need a generic way to deal with it.

Yes if you have any ideas let me know. As Will had mentioned it would be
good to have a common function table all these devices could use too. I
will take a closer look at what you have.

I had started on a CTI driver much in line with your current
implementation but your approach looks good to me.

Looking at the code though, I couldn't find a way to perform a
mapping between two different CTIs. Reason I ask is because we
have use cases where we need to map one CTIs input to another
CTIs output on the same channel.

Do you intend to support different entities within kernel to map
different trig_in or trig_out on the same CTI? If so, it might
probably require reference counting for the enable/disable.

What user interface do you plan to provide for the CTI? Maybe
something consistent with other CoreSight components in sysfs to
allow users to enable, disable, map and unmap ???

Please let me know your thoughts.

CTIs can easily be made part of the CoreSight core layer using a
different type but apart from being part of the CoreSight list
containing all the trace and CTI components, not sure if there is
anything that is useful to do in the core layer. Need to think
about this.

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