Re: [PATCH v5 3/9] drm/i915: Drop AUX backlight enable check for backlight control

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 10 May 2017, "Pandiyan, Dhinakaran" <dhinakaran.pandiyan@intel.com> wrote:
> On Tue, 2017-05-09 at 16:39 -0700, Puthikorn Voravootivat wrote:
>> > How is backlight enabled in this case?
>> Using eDP BL_ENABLE pin
>
>
> Sure, but I am not seeing how this falls back to one of the
> [bxt,lpt]_enable_backlight() functions in intel_panel.c. Apologies if I
> am missing something very obvious.
>
> If intel_dp_aux_init_backlight_funcs() returned -ENODEV, then one of the
> platform specific PWM enable callbacks would be called. But in this
> case, dp_aux_enable_backlight() just returns without doing anything.

The eDP BL_ENABLE pin (in the physical eDP connector) is controlled by
the panel power sequencer, independent from the PWM control. See
intel_edp_backlight_* functions in intel_dp.c.

BR,
Jani.


>
>
> -DK
>> 
>> 
>> On Sat, May 6, 2017 at 1:59 AM, Pandiyan, Dhinakaran
>> <dhinakaran.pandiyan@intel.com> wrote:
>>         On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat
>>         wrote:
>>         > There are some panel that
>>         > (1) does not support display backlight enable via AUX
>>         > (2) support display backlight adjustment via AUX
>>         > (3) support display backlight enable via eDP BL_ENABLE pin
>>         >
>>         > The current driver required that (1) must be support to
>>         enable (2).
>>         > This patch drops that requirement.
>>         >
>>         > Signed-off-by: Puthikorn Voravootivat <puthik@chromium.org>
>>         > ---
>>         >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 5 ++++-
>>         >  1 file changed, 4 insertions(+), 1 deletion(-)
>>         >
>>         > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
>>         b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
>>         > index ad8560c5f689..5b83c9737644 100644
>>         > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
>>         > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
>>         > @@ -28,6 +28,10 @@ static void
>>         set_aux_backlight_enable(struct intel_dp *intel_dp, bool
>>         enable)
>>         >  {
>>         >       uint8_t reg_val = 0;
>>         >
>>         > +       /* Early return when display use other mechanism to
>>         enable backlight. */
>>         > +     if (!(intel_dp->edp_dpcd[1] &
>>         DP_EDP_BACKLIGHT_AUX_ENABLE_CAP))
>>         > +             return;
>>         > +
>>         
>>         How is backlight enabled in this case?
>>         
>>         -DK
>>         
>>         >       if (drm_dp_dpcd_readb(&intel_dp->aux,
>>         DP_EDP_DISPLAY_CONTROL_REGISTER,
>>         >                             &reg_val) < 0) {
>>         >               DRM_DEBUG_KMS("Failed to read DPCD register 0x
>>         %x\n",
>>         > @@ -164,7 +168,6 @@
>>         intel_dp_aux_display_control_capable(struct intel_connector
>>         *connector)
>>         >        * the panel can support backlight control over the
>>         aux channel
>>         >        */
>>         >       if ((intel_dp->edp_dpcd[1] &
>>         DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP) &&
>>         > -         (intel_dp->edp_dpcd[1] &
>>         DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
>>         >           (intel_dp->edp_dpcd[2] &
>>         DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
>>         >               DRM_DEBUG_KMS("AUX Backlight Control
>>         Supported!\n");
>>         >               return true;
>>         
>>         
>> 
>> 
>> _______________________________________________
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>> Intel-gfx@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>

-- 
Jani Nikula, Intel Open Source Technology Center
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