On Wed, 08 Mar 2017, Puthikorn Voravootivat <puthik@xxxxxxxxxxxx> 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 <puthik@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 29 +++++++++++++++++++++------
> 1 file changed, 23 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 abfb09c1269f..16cd1265d264 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -101,15 +101,32 @@ 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));
That's clearly bonkers, it ends up selecting
DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT by accident, not
DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD, because it doesn't mask the bits.
> + if (!drm_dp_dpcd_readb(&intel_dp->aux,
> + DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf)) {
> + 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:
> + dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> + dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> + drm_dp_dpcd_writeb(&intel_dp->aux,
> + DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf);
> + break;
> +
> + /* Do nothing in these cases */
> + case DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD:
> + case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT:
Based on the current requirements for using DPCD backlight control, the
only power-on default we should end up here with is
DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET.
In particular, I don't think we should accept the PRODUCT mode without
ensuring we output PWM to the eDP pins as well. And currently DPCD and
PWM controls are mutually exclusive.
BR,
Jani.
> + default:
> + break;
> + }
> }
>
> static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
--
Jani Nikula, Intel Open Source Technology Center
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