[PATCH v7 3/9] drm/i915: Drop AUX backlight enable check for backlight control

[Puthikorn Voravootivat]

On Fri, May 12, 2017 at 6:14 AM, Jani Nikula <jani.nikula at linux.intel.com>
wrote:

> On Fri, 12 May 2017, "Pandiyan, Dhinakaran" <dhinakaran.pandiyan at intel.com>
> wrote:
> > On Thu, 2017-05-11 at 16:02 -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.
> >>
> >
> > You sent this version before I finished my follow-up questions, copying
> > the conversation here for context.
>
> Puthikorn, please don't send new versions before the review is
> addressed.
>
Sorry I thought I was explained it clear enough.

>
> Pushed patches 1, 2, 5, and 7. Thanks for the patches and review.
>
> BR,
> Jani.
>
> > DK: Won't DP_EDP_BACKLIGHT_AUX_ENABLE_CAP be 1 always? The code below,
> > in
> > intel_dp_aux_display_control_capable(), makes sure
> > DP_EDP_BACKLIGHT_PIN_ENABLE_CAP=0. The spec says at least one of these
> > has to be 1.
> >
> > Puthikorn: We will drop the  DP_EDP_BACKLIGHT_PIN_ENABLE_CAP != 0 check
> > in next patch set.
> > This patch adds check here to prepare for that.
> >
> >
> > 1) So, this patch does not really fix what the commit message claims
> > because it is dependent on the following patch. Does it make sense to
> > remove this check in this patch? That way, this patch by itself is the
> > fix that the commit message says.
> >
> > -           !((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP)
> >
>
Sure. I can remove this here and adds it in next patch instead.

>
> > 2) If a panel supports backlight enable via AUX and BL_ENABLE pin, this
> > patch (along with the next) enables backlight twice, doesn't it?
> > _intel_edp_backlight_on(intel_dp) in intel_dp.c is called
> > unconditionally after intel_dp_aux_enable_backlight(). I don't know how
> > likely this configuration is or if it's alright to enable via both AUX
> > and BL_ENABLE pin.
> >
>
The eDP spec did not mention this case explicitly.
But it should not hurt to enable backlight twice as we want the backlight
to be enabled anyway.


> >
> >
> >
> >> Signed-off-by: Puthikorn Voravootivat <puthik at 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 870c03fc0f3a..c22712762957 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;
> >> +
> >>      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)
> &&
> >>          !((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP) ||
> >>            (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)))
> {
> >
>
> --
> Jani Nikula, Intel Open Source Technology Center
>
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