[Intel-gfx] [PATCH v2 0/4] drm/dp, drm/i915: Finish basic PWM support for VESA backlight helpers

[Hans de Goede]

Hi,

On 10/7/21 11:54 AM, Hans de Goede wrote:
> Hi,
> 
> On 10/5/21 10:26 PM, Lyude Paul wrote:
>> On Sat, 2021-10-02 at 11:14 +0200, Hans de Goede wrote:
>>> Hi Lyude,
>>>
>>> On 10/2/21 12:53 AM, Lyude Paul wrote:
>>>> When I originally moved all of the VESA backlight code in i915 into DRM
>>>> helpers, one of the things I didn't have the hardware or time for
>>>> testing was machines that used a combination of PWM and DPCD in order to
>>>> control their backlights. This has since then caused some breakages and
>>>> resulted in us disabling DPCD backlight support on such machines. This
>>>> works fine, unless you have a machine that actually needs this
>>>> functionality for backlight controls to work at all. Additionally, we
>>>> will need to support PWM for when we start adding support for VESA's
>>>> product (as in the product of multiplication) control mode for better
>>>> brightness ranges.
>>>>
>>>> So - let's finally finish up implementing basic support for these types
>>>> of backlights to solve these problems in our DP helpers, along with
>>>> implementing support for this in i915. And since digging into this issue
>>>> solved the last questions we really had about probing backlights in i915
>>>> for the most part, let's update some of the comments around that as
>>>> well!
>>>
>>> Backlight control is a topic which I'm reasonably familiar with,
>>> do you want me to review this series for you ?
>>
>> Possibly, although I definitely want to make sure that someone from Intel gets
>> a chance to review this as well.
> 
> I already expected you would also want someone from Intel to take a look
> as well :)
> 
> So to figure out if I have system to test this I ended up taking a close
> look at the code, which was a nice learning experience. Interesting how
> some panels use a combination of DCPD + pwm/gpio for enable/disable and/or
> pwm for brightness level control.
> 
> I wonder though what DCPD still does if pwm is used for both the
> enable/disable and brightness-level control ?
> 
> Since I was taking a close look already I decided to do turn this into
> a full, the entire set looks good to me:
> 
> Reviewed-by: Hans de Goede <hdegoede at redhat.com>
> 
>> I'm more curious if you might happen to have
>> any systems that would be able to test this.
> 
> I don't believe I have a system where I can test this, The only systems
> which I have which presumably (I did not check) use eDP / DCPD backlight
> control are boring ThinkPads with only i915 gfx.

Continuing with reading my email I see that you've also posted a v5
with 1 new patch:

[PATCH v3 3/5] drm/dp: Disable unsupported features in DP_EDP_BACKLIGHT_MODE_SET_REGISTER

That patch looks good to me too, so you may also add my:

Reviewed-by: Hans de Goede <hdegoede at redhat.com>

To that one / to the entire v3 series.

Regards,

Hans



>>>> Changes:
>>>> * Fixup docs
>>>> * Add patch to stop us from breaking nouveau
>>>>
>>>> Lyude Paul (4):
>>>>   drm/i915: Add support for panels with VESA backlights with PWM
>>>>     enable/disable
>>>>   drm/nouveau/kms/nv50-: Explicitly check DPCD backlights for aux
>>>>     enable/brightness
>>>>   drm/dp, drm/i915: Add support for VESA backlights using PWM for
>>>>     brightness control
>>>>   drm/i915: Clarify probing order in intel_dp_aux_init_backlight_funcs()
>>>>
>>>>  drivers/gpu/drm/drm_dp_helper.c               | 75 +++++++++++------
>>>>  .../drm/i915/display/intel_dp_aux_backlight.c | 80 ++++++++++++++-----
>>>>  drivers/gpu/drm/nouveau/nouveau_backlight.c   |  5 +-
>>>>  include/drm/drm_dp_helper.h                   |  7 +-
>>>>  4 files changed, 122 insertions(+), 45 deletions(-)
>>>>
>>>
>>