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

[Puthikorn Voravootivat <puthik@xxxxxxxxxxxx>]

> How is backlight enabled in this case?

Using eDP BL_ENABLE pin

On Sat, May 6, 2017 at 1:59 AM, Pandiyan, Dhinakaran <dhinakaran.pandiyan@xxxxxxxxx> 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@xxxxxxxxxxxx>
> ---
>  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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