Re: [PATCH] drm/i915: Add a DRM property "psr"

Jani Nikula
2014-03-20T10:52:13Z

On Wed, 19 Mar 2014, Siva Chandra <sivachandra@google.com> wrote:
> On Wed, Mar 19, 2014 at 8:03 AM, Damien Lespiau
> <damien.lespiau@intel.com> wrote:
>> On Wed, Mar 19, 2014 at 09:44:38AM +0100, Daniel Vetter wrote:
>>> On Tue, Mar 18, 2014 at 01:53:56PM -0700, Siva Chandra wrote:
>>> > We are testing a few PSR panels; Having a knob to turn PSR on and off
>>> > would be of great convenience for manual testing and for test scripts.
>>>
>>> Is the module param not good enough for that? Iirc we recheck that every
>>> time ...
>>
>> (the module parameter is accessible through a file in sysfs:
>> /sys/module/i915/parameters/enable_psr)
>
> As I mentioned in the other mail, this param is not active and I
> couldn't think of any neat solution to make it active.
>
>> Alternatively, doesn't it look like something that belongs to debugfs?
>> ie not an API with a stability guarantee?
>
> PSR is part of the eDP standard now. Also, we are only bringing in an
> on/off knob. Is really going to cause us stability issues?

The point is, if we add this, we need to support and maintain it until
the end of time, i.e. the ABI must remain stable. It is quite a
commitment to make.

If this is for testing only, and the module parameter does not quite cut
it, please add it to debugfs. That we can pretty much change at will.

BR,
Jani.

>
> Thanks,
> Siva Chandra
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--
Jani Nikula, Intel Open Source Technology Center