Nouveau - Oct 2021 - [Intel-gfx] [PATCH v2 0/4] drm/dp, drm/i915: Finish basic PWM support for VESA backlight helpers

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 ?

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(-)
>

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'm more curious if you might happen to
have
any systems that would be able to test this.
> 
> 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(-)
> > 
> 
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat