[Intel-gfx] [PATCH v12 3/3] drm/i915: Add option to support dynamic backlight via DPCD
Pandiyan, Dhinakaran
dhinakaran.pandiyan at intel.com
Tue Jun 27 22:29:33 UTC 2017
On Tue, 2017-06-27 at 16:23 +0300, David Weinehall wrote:
> On Mon, Jun 26, 2017 at 05:18:19PM +0300, David Weinehall wrote:
> > On Thu, Jun 22, 2017 at 12:03:39PM -0700, Puthikorn Voravootivat wrote:
> > > This patch adds option to enable dynamic backlight for eDP
> > > panel that supports this feature via DPCD register and
> > > set minimum / maximum brightness to 0% and 100% of the
> > > normal brightness.
> >
> > This patch causes a regression on my ThinkPad X1 Carbon Gen 4;
> > with enable_dbc = true the backlight stays off; setting i915.enable_dbc=0
> > on boot makes things work properly again.
>
> Some more testing indicates that while i915.enable_dbc=0 solves the
> initial issue of backlight not coming on, it's not enough--after
> suspend/resume the backlight stays off.
>
> Passing i915.enable_dpcd_backlight=0 seems to work both for the initial
> case of backlight not coming on at boot, and the issue with backlight
> not coming on after suspend/resume.
>
> So:
>
> DBC:1, DPCD: -1: blank screen on boot
> DBC:0, DPCD: -1: screen OK on boot, blank after suspend/resume
> DBC:1, DPCD: 0: screen OK on boot, screen OK after suspend/resume
> DBC:0, DPCD: 0: screen OK on boot, screen OK after suspend/resume
>
> So it seems that at least for the ThinkPad X1 Carbon Gen 4 (possibly
> limited to the 2560x1440 model) DPCD backlight isn't supported.
>
Hi David,
Thanks for the bug report. It's come a bit sooner than I expected
though.
We shouldn't be enabling DPCD backlight control if the panel does not
support it. I'd like to look at the dmesg with drm.debug=0xE. We debug
log the panel capabilities early during boot and that will be useful.
Can you also provide the output of i915_dpcd in debugfs for the eDP
connector?
I guess it makes sense to file an FDO and attach the logs there.
-DK
> Or possibly something is wrong with the DPCD backlight patch.
>
> > > Signed-off-by: Puthikorn Voravootivat <puthik at chromium.org>
> > > Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > > ---
> > > drivers/gpu/drm/i915/i915_params.c | 5 +++++
> > > drivers/gpu/drm/i915/i915_params.h | 3 ++-
> > > drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 26 ++++++++++++++++++++++++++
> > > 3 files changed, 33 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> > > index 5b5ab15d191f..88b9d3e6713a 100644
> > > --- a/drivers/gpu/drm/i915/i915_params.c
> > > +++ b/drivers/gpu/drm/i915/i915_params.c
> > > @@ -65,6 +65,7 @@ struct i915_params i915 __read_mostly = {
> > > .inject_load_failure = 0,
> > > .enable_dpcd_backlight = -1,
> > > .enable_gvt = false,
> > > + .enable_dbc = true,
> > > };
> > >
> > > module_param_named(modeset, i915.modeset, int, 0400);
> > > @@ -254,3 +255,7 @@ MODULE_PARM_DESC(enable_dpcd_backlight,
> > > module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
> > > MODULE_PARM_DESC(enable_gvt,
> > > "Enable support for Intel GVT-g graphics virtualization host support(default:false)");
> > > +
> > > +module_param_named_unsafe(enable_dbc, i915.enable_dbc, bool, 0600);
> > > +MODULE_PARM_DESC(enable_dbc,
> > > + "Enable support for dynamic backlight control (default:true)");
> > > diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> > > index 0d6cf9138dc4..057e203e6bda 100644
> > > --- a/drivers/gpu/drm/i915/i915_params.h
> > > +++ b/drivers/gpu/drm/i915/i915_params.h
> > > @@ -67,7 +67,8 @@
> > > func(bool, verbose_state_checks); \
> > > func(bool, nuclear_pageflip); \
> > > func(bool, enable_dp_mst); \
> > > - func(bool, enable_gvt)
> > > + func(bool, enable_gvt); \
> > > + func(bool, enable_dbc)
> > >
> > > #define MEMBER(T, member) T member
> > > struct i915_params {
> > > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > index fea161727c6e..b25cd88fc1c5 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > @@ -173,6 +173,24 @@ static bool intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
> > > return true;
> > > }
> > >
> > > +/*
> > > +* Set minimum / maximum dynamic brightness percentage. This value is expressed
> > > +* as the percentage of normal brightness in 5% increments.
> > > +*/
> > > +static bool
> > > +intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp *intel_dp,
> > > + u32 min, u32 max)
> > > +{
> > > + u8 dbc[] = { DIV_ROUND_CLOSEST(min, 5), DIV_ROUND_CLOSEST(max, 5) };
> > > +
> > > + if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
> > > + dbc, sizeof(dbc)) < 0) {
> > > + DRM_DEBUG_KMS("Failed to write aux DBC brightness level\n");
> > > + return false;
> > > + }
> > > + return true;
> > > +}
> > > +
> > > static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_state,
> > > const struct drm_connector_state *conn_state)
> > > {
> > > @@ -208,6 +226,14 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
> > > if (intel_dp_aux_set_pwm_freq(connector))
> > > new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> > >
> > > + if (i915.enable_dbc &&
> > > + (intel_dp->edp_dpcd[2] & DP_EDP_DYNAMIC_BACKLIGHT_CAP)) {
> > > + if(intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0, 100)) {
> > > + new_dpcd_buf |= DP_EDP_DYNAMIC_BACKLIGHT_ENABLE;
> > > + DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> > > + }
> > > + }
> > > +
> > > if (new_dpcd_buf != dpcd_buf) {
> > > if (drm_dp_dpcd_writeb(&intel_dp->aux,
> > > DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {
> > > --
> > > 2.13.1.611.g7e3b11ae1-goog
> > >
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