On Fri, 2017-05-26 at 18:42 -0700, Puthikorn Voravootivat wrote:
> Add heuristic to decide that AUX or PWM pin should use for
> backlight brightness adjustment and modify i915 param description
> to have auto, force disable, and force enable.
>
> The heuristic to determine that using AUX pin is better than using
> PWM pin is that the panel support any of the feature list here.
> - Regional backlight brightness adjustment
> - Backlight PWM frequency set
> - More than 8 bits resolution of brightness level
> - Backlight enablement via AUX and not by BL_ENABLE pin
>
> Signed-off-by: Puthikorn Voravootivat <puthik@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_params.c | 7 +--
> drivers/gpu/drm/i915/i915_params.h | 2 +-
> drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 64 +++++++++++++++++++++++++--
> 3 files changed, 66 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index b6a7e363d076..3758ae1f11b4 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -63,7 +63,7 @@ struct i915_params i915 __read_mostly = {
> .huc_firmware_path = NULL,
> .enable_dp_mst = true,
> .inject_load_failure = 0,
> - .enable_dpcd_backlight = false,
> + .enable_dpcd_backlight = -1,
> .enable_gvt = false,
> };
>
> @@ -246,9 +246,10 @@ MODULE_PARM_DESC(enable_dp_mst,
> module_param_named_unsafe(inject_load_failure, i915.inject_load_failure, uint, 0400);
> MODULE_PARM_DESC(inject_load_failure,
> "Force an error after a number of failure check points (0:disabled (default), N:force failure at the Nth failure check point)");
> -module_param_named(enable_dpcd_backlight, i915.enable_dpcd_backlight, bool, 0600);
> +module_param_named_unsafe(enable_dpcd_backlight, i915.enable_dpcd_backlight, int, 0600);
> MODULE_PARM_DESC(enable_dpcd_backlight,
> - "Enable support for DPCD backlight control (default:false)");
> + "Enable support for DPCD backlight control "
> + "(-1:auto (default), 0:force disable, 1:force enabled if supported");
>
> module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
> MODULE_PARM_DESC(enable_gvt,
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index 34148cc8637c..ac02efce6e22 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -66,7 +66,7 @@
> func(bool, verbose_state_checks); \
> func(bool, nuclear_pageflip); \
> func(bool, enable_dp_mst); \
> - func(bool, enable_dpcd_backlight); \
> + func(int, enable_dpcd_backlight); \
> func(bool, enable_gvt)
>
> #define MEMBER(T, member) T member
> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> index a0995c00fc84..c89aae804659 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -43,6 +43,9 @@ static void set_aux_backlight_enable(struct intel_dp *intel_dp, bool enable)
> else
> reg_val &= ~(DP_EDP_BACKLIGHT_ENABLE);
>
> + /* TODO: If the panel also support enabling backlight via BL_ENABLE pin,
> + * the backlight will be enabled again in _intel_edp_backlight_on()
> + */
Unrelated hunk, please remove. This should have been included in one of
the previous patches.
> if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
> reg_val) != 1) {
> DRM_DEBUG_KMS("Failed to %s aux backlight\n",
> @@ -168,15 +171,66 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector)
> /* Check the eDP Display control capabilities registers to determine if
> * 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[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP) &&
> - !(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) {
> + if ((intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP) &&
> + (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
> DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
> return true;
> }
> return false;
> }
>
> +/*
> + * Heuristic function whether we should use AUX for backlight adjustment or not.
> + *
> + * We should use AUX for backlight brightness adjustment if panel doesn't this
> + * via PWM pin or using AUX is better than using PWM pin.
> + *
> + * The heuristic to determine that using AUX pin is better than using PWM pin is
> + * that the panel support any of the feature list here.
> + * - Regional backlight brightness adjustment
> + * - Backlight PWM frequency set
> + * - More than 8 bits resolution of brightness level
> + * - Backlight enablement via AUX and not by BL_ENABLE pin
> + *
> + * If all above are not true, assume that using PWM pin is better.
> + */
> +static bool
> +intel_dp_aux_display_control_heuristic(struct intel_connector *connector)
> +{
> + struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
> + uint8_t reg_val;
> +
> + /* Panel doesn't support adjusting backlight brightness via PWN pin */
> + if (!(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP))
Isn't BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP in edp_dpcd[2] ?
> + return true;
> +
> + /* Panel supports regional backlight brightness adjustment */
> + if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_GENERAL_CAP_3,
Spec says this register is new to eDP 1.4. I don't see a check for
version.
> + ®_val) != 1) {
> + DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> + DP_EDP_GENERAL_CAP_3);
> + return false;
> + }
> + if (reg_val > 0)
> + return true;
> +
> + /* Panel supports backlight PWM frequency set */
> + if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP)
> + return true;
> +
> + /* Panel supports more than 8 bits resolution of brightness level */
> + if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
> + return true;
I don't know if more than 8 bits is relatively better than the
resolution PWM pin allows. I guess, we could fix that later by comparing
the number of brightness levels.
> +
> + /* Panel supports enabling backlight via AUX but not by BL_ENABLE pin */
> + if ((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> + !(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP))
> + return true;
> +
> + return false;
> +
> +}
> +
> int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
> {
> struct intel_panel *panel = &intel_connector->panel;
> @@ -187,6 +241,10 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
> if (!intel_dp_aux_display_control_capable(intel_connector))
> return -ENODEV;
>
> + if (i915.enable_dpcd_backlight == -1 &&
> + !intel_dp_aux_display_control_heuristic(intel_connector))
> + return -ENODEV;
> +
> panel->backlight.setup = intel_dp_aux_setup_backlight;
> panel->backlight.enable = intel_dp_aux_enable_backlight;
> panel->backlight.disable = intel_dp_aux_disable_backlight;
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