On Fri, 26 Jun 2015, Jani Nikula <jani.nikula@xxxxxxxxx> wrote: > Some 855gm models (at least ThinkPad X40) regressed because of > > commit b0cd324faed23d10d66ba6ade66579c681feef6f > Author: Jani Nikula <jani.nikula@xxxxxxxxx> > Date: Wed Nov 12 16:25:43 2014 +0200 > > drm/i915: don't save/restore backlight hist ctl registers > > which tried to make our driver more robust by not blindly saving and > restoring registers, but it failed to take into account > > commit 0eb96d6ed38430b72897adde58f5477a6b71757a > Author: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> > Date: Wed Oct 14 12:33:41 2009 -0700 > > drm/i915: save/restore BLC histogram control reg across suspend/resume > > Fix the regression by enabling hist ctl on gen2. > > v2: Improved the comment. > > v3: Improved the comment, again. > > Reported-and-tested-by: Philipp Gesang <phg@xxxxxxxxxxxxx> > References: http://mid.gmane.org/20150623222648.GD12335@acheron > Fixes: b0cd324faed2 ("drm/i915: don't save/restore backlight hist ctl registers") > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Acked-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Pushed to drm-intel-next-fixes, assuming Chris' ack and Philipp's tested-by are enough. BR, Jani. > --- > drivers/gpu/drm/i915/i915_reg.h | 1 + > drivers/gpu/drm/i915/intel_panel.c | 8 ++++++++ > 2 files changed, 9 insertions(+) > > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h > index fa9ccb87eb66..bf7c08b94088 100644 > --- a/drivers/gpu/drm/i915/i915_reg.h > +++ b/drivers/gpu/drm/i915/i915_reg.h > @@ -3507,6 +3507,7 @@ enum skl_disp_power_wells { > #define BLM_POLARITY_PNV (1 << 0) /* pnv only */ > > #define BLC_HIST_CTL (dev_priv->info.display_mmio_offset + 0x61260) > +#define BLM_HISTOGRAM_ENABLE (1 << 31) > > /* New registers for PCH-split platforms. Safe where new bits show up, the > * register layout machtes with gen4 BLC_PWM_CTL[12]. */ > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c > index 7d83527f95f7..55aad2322e10 100644 > --- a/drivers/gpu/drm/i915/intel_panel.c > +++ b/drivers/gpu/drm/i915/intel_panel.c > @@ -907,6 +907,14 @@ static void i9xx_enable_backlight(struct intel_connector *connector) > > /* XXX: combine this into above write? */ > intel_panel_actually_set_backlight(connector, panel->backlight.level); > + > + /* > + * Needed to enable backlight on some 855gm models. BLC_HIST_CTL is > + * 855gm only, but checking for gen2 is safe, as 855gm is the only gen2 > + * that has backlight. > + */ > + if (IS_GEN2(dev)) > + I915_WRITE(BLC_HIST_CTL, BLM_HISTOGRAM_ENABLE); > } > > static void i965_enable_backlight(struct intel_connector *connector) > -- > 2.1.4 > -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
