On Fri, 2017-06-02 at 17:42 +0000, Pandiyan, Dhinakaran wrote:
Somehow the CC's got removed in my previous reply, adding them back. See
one additional comment below.
> 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); \
Please move this above the bools, see comment in code that's a few lines
above.
-DK
> > 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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