On Wed, 2017-05-03 at 17:28 -0700, Puthikorn Voravootivat wrote:
> intel_dp_aux_enable_backlight() assumed that the register
> BACKLIGHT_BRIGHTNESS_CONTROL_MODE can only has value 01
> (DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET) when initialize.
>
> This patch fixed that by handling all cases of that register.
>
> Signed-off-by: Puthikorn Voravootivat <put...@chromium.org>
Spec says both 0x00 and 0x01 are possible power-on defaults. So,
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandi...@intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 33
> ++++++++++++++++++++++-----
> 1 file changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> index 24a905d1a74b..ad8560c5f689 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -97,15 +97,36 @@ static void intel_dp_aux_enable_backlight(struct
> intel_connector *connector)
> {
> struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
> uint8_t dpcd_buf = 0;
> + uint8_t edp_backlight_mode = 0;
>
> set_aux_backlight_enable(intel_dp, true);
>
> - if ((drm_dp_dpcd_readb(&intel_dp->aux,
> - DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf)
> == 1) &&
> - ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> - DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET))
> - drm_dp_dpcd_writeb(&intel_dp->aux,
> DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> - (dpcd_buf |
> DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD));
> + if (drm_dp_dpcd_readb(&intel_dp->aux,
> + DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf) != 1) {
> + DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> + DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> + return;
> + }
> +
> + edp_backlight_mode = dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> +
> + switch (edp_backlight_mode) {
> + case DP_EDP_BACKLIGHT_CONTROL_MODE_PWM:
> + case DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET:
> + case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT:
> + dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> + dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> + if (drm_dp_dpcd_writeb(&intel_dp->aux,
> + DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf) < 0) {
> + DRM_DEBUG_KMS("Failed to write aux backlight mode\n");
> + }
> + break;
> +
> + /* Do nothing when it is already DPCD mode */
> + case DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD:
> + default:
> + break;
> + }
> }
>
> static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
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