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    SubjectRe: [PATCH] drm/i915: quirk no PCH_PWM_ENABLE for Dell XPS13 backlight
    On Fri, Jul 19, 2013 at 03:02:01PM -0700, Kamal Mostafa wrote:
    > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=47941
    > BugLink: https://bugs.launchpad.net/bugs/1163720
    > BugLink: https://bugs.launchpad.net/bugs/1162026
    >
    > Some machines suffer from non-functional backlight controls if
    > BLM_PCH_PWM_ENABLE is set, so provide a quirk to avoid doing so.
    > Apply this quirk to Dell XPS 13 models.
    >
    > Tested-by: Eric Griffith <EGriffith92@gmail.com>
    > Tested-by: Kent Baxley <kent.baxley@canonical.com>
    > Cc: <stable@vger.kernel.org> # v3.8+
    > Signed-off-by: Kamal Mostafa <kamal@canonical.com>

    I still wonder what exactly's going on here, but for backlight stuff I've
    given up on avoiding quirks ;-) Thanks for digging into this, patch
    applied to -fixes.
    -Daniel

    > ---
    > drivers/gpu/drm/i915/i915_drv.h | 1 +
    > drivers/gpu/drm/i915/intel_display.c | 16 ++++++++++++++++
    > drivers/gpu/drm/i915/intel_panel.c | 3 ++-
    > 3 files changed, 19 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
    > index a416645..204c3ec 100644
    > --- a/drivers/gpu/drm/i915/i915_drv.h
    > +++ b/drivers/gpu/drm/i915/i915_drv.h
    > @@ -555,6 +555,7 @@ enum intel_sbi_destination {
    > #define QUIRK_PIPEA_FORCE (1<<0)
    > #define QUIRK_LVDS_SSC_DISABLE (1<<1)
    > #define QUIRK_INVERT_BRIGHTNESS (1<<2)
    > +#define QUIRK_NO_PCH_PWM_ENABLE (1<<3)
    >
    > struct intel_fbdev;
    > struct intel_fbc_work;
    > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
    > index 85f3eb7..42e207e 100644
    > --- a/drivers/gpu/drm/i915/intel_display.c
    > +++ b/drivers/gpu/drm/i915/intel_display.c
    > @@ -9398,6 +9398,17 @@ static void quirk_invert_brightness(struct drm_device *dev)
    > DRM_INFO("applying inverted panel brightness quirk\n");
    > }
    >
    > +/*
    > + * Some machines (Dell XPS13) suffer broken backlight controls if
    > + * BLM_PCH_PWM_ENABLE is set.
    > + */
    > +static void quirk_no_pcm_pwm_enable(struct drm_device *dev)
    > +{
    > + struct drm_i915_private *dev_priv = dev->dev_private;
    > + dev_priv->quirks |= QUIRK_NO_PCH_PWM_ENABLE;
    > + DRM_INFO("applying no-PCH_PWM_ENABLE quirk\n");
    > +}
    > +
    > struct intel_quirk {
    > int device;
    > int subsystem_vendor;
    > @@ -9467,6 +9478,11 @@ static struct intel_quirk intel_quirks[] = {
    >
    > /* Acer Aspire 4736Z */
    > { 0x2a42, 0x1025, 0x0260, quirk_invert_brightness },
    > +
    > + /* Dell XPS13 HD Sandy Bridge */
    > + { 0x0116, 0x1028, 0x052e, quirk_no_pcm_pwm_enable },
    > + /* Dell XPS13 HD and XPS13 FHD Ivy Bridge */
    > + { 0x0166, 0x1028, 0x058b, quirk_no_pcm_pwm_enable },
    > };
    >
    > static void intel_init_quirks(struct drm_device *dev)
    > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
    > index 80bea1d..01b5a51 100644
    > --- a/drivers/gpu/drm/i915/intel_panel.c
    > +++ b/drivers/gpu/drm/i915/intel_panel.c
    > @@ -580,7 +580,8 @@ void intel_panel_enable_backlight(struct drm_device *dev,
    > POSTING_READ(reg);
    > I915_WRITE(reg, tmp | BLM_PWM_ENABLE);
    >
    > - if (HAS_PCH_SPLIT(dev)) {
    > + if (HAS_PCH_SPLIT(dev) &&
    > + !(dev_priv->quirks & QUIRK_NO_PCH_PWM_ENABLE)) {
    > tmp = I915_READ(BLC_PWM_PCH_CTL1);
    > tmp |= BLM_PCH_PWM_ENABLE;
    > tmp &= ~BLM_PCH_OVERRIDE_ENABLE;
    > --
    > 1.8.1.2
    >

    --
    Daniel Vetter
    Software Engineer, Intel Corporation
    +41 (0) 79 365 57 48 - http://blog.ffwll.ch


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