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@xxxxxxxxxx> > 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. 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(-) >>> >> >
