[Intel-gfx] [PATCH] drm/i915: add psr toggle to debugfs

[Eric Caruso]

On Wed, Apr 15, 2015 at 2:39 PM, Rodrigo Vivi <rodrigo.vivi at gmail.com> wrote:
> On Fri, Mar 13, 2015 at 1:46 PM, Eric Caruso <ejcaruso at chromium.org> wrote:
>> On Fri, Mar 13, 2015 at 1:14 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
>>> 2015-03-13 16:01 GMT-03:00 Daniel Vetter <daniel at ffwll.ch>:
>>>> On Fri, Mar 13, 2015 at 7:10 PM, Eric Caruso <ejcaruso at chromium.org> wrote:
>>>>> This patch allows userspace to toggle PSR through a debugfs interface.
>>>>> It adds functionality to write 0 or 1 to the existing
>>>>> i915_edp_psr_status file in order to change the relevant module
>>>>> parameter and enable/disable PSR.
>>>>>
>>>>> Previous upstream feedback did not like making it a connector property
>>>>> or putting it in sysfs because that would require API stability going
>>>>> forward. debugfs interfaces do not have this restriction.
>>>>>
>>>>> Signed-off-by: Eric Caruso <ejcaruso at chromium.org>
>>>>
>>>> What do we need this for? debugfs is generally for debugging (where
>>>> the module option should be enough) and for testcases (which doesn't
>>>> seem to be the case here).
>>>
>>> What is wrong with "echo 1 > /sys/module/i915/parameters/enable_psr"?
>>>
>>>> -Daniel
>>>> --
>>>> Daniel Vetter
>>>> Software Engineer, Intel Corporation
>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>>>> _______________________________________________
>>>> Intel-gfx mailing list
>>>> Intel-gfx at lists.freedesktop.org
>>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>>
>>>
>>>
>>> --
>>> Paulo Zanoni
>>
>> Forgive me if this is wrong, but updating the module parameter doesn't
>> change whether or not PSR is enabled immediately. You need to go through
>> intel_enable_ddi for this to take effect.
>
> indeed.
>
>>
>> We were using something like this for testing on Chromium OS, because
>> PSR would sometimes cause issues. This allows us to change the module
>> parameter and enable/disable PSR in one step.
>
> I like the idea. But I'd prefer a sysfs toggle interface though...

Aren't you adding a connector property at this point? If so, it seems like both
this debugfs knob and a hypothetical sysfs interface would both be unnecessary.
(see: http://lists.freedesktop.org/archives/intel-gfx/2015-March/063074.html)

>
>>
>> The upstream feedback I mentioned was done about a year ago:
>> http://lists.freedesktop.org/archives/intel-gfx/2014-March/041896.html
>> It seemed to favor a debugfs knob for this.
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>
>
> --
> Rodrigo Vivi
> Blog: http://blog.vivi.eng.br