Re: [PATCH v2] drm/i915/edp: Add a T12 panel delay quirk to fix DP AUX CH timeouts

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jun 29, 2017 at 01:41:16PM -0700, Manasi Navare wrote:
> Thanks for the review comments. Please find my responses below:
> 
> On Thu, Jun 29, 2017 at 11:24:48PM +0300, Ville Syrjälä wrote:
> > On Wed, Jun 28, 2017 at 05:14:31PM -0700, Manasi Navare wrote:
> > > This patch fixes the DP AUX CH timeouts observed during CI IGT
> > > tests thus fixing the CI failures. This is done by adding a
> > > quirk for a particular PCI device that requires the panel power
> > > cycle delay (T12) to be 300msecs more than the minimum value
> > > specified in the eDP spec. So a quirk is implemented for that
> > > specific PCI device.
> > > 
> > > v2:
> > > * Change the function and variable names to from PPS_T12_
> > > to _T12 since it is a T12 delay (Clint)
> > > 
> > > Fixes: FDO #101144 #101515 #101154 #101167
> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > > Cc: Cinton Taylor <clinton.a.taylor@intel.com>
> > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.h      |  1 +
> > >  drivers/gpu/drm/i915/intel_display.c | 12 ++++++++++++
> > >  drivers/gpu/drm/i915/intel_dp.c      | 12 ++++++++++++
> > >  3 files changed, 25 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > > index 427d10c..4327c8a 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > @@ -1168,6 +1168,7 @@ enum intel_sbi_destination {
> > >  #define QUIRK_INVERT_BRIGHTNESS (1<<2)
> > >  #define QUIRK_BACKLIGHT_PRESENT (1<<3)
> > >  #define QUIRK_PIN_SWIZZLED_PAGES (1<<5)
> > > +#define QUIRK_INCREASE_T12_DELAY (1<<6)
> > >  
> > >  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 4e03ca6..37beb62 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -14765,6 +14765,15 @@ static void quirk_backlight_present(struct drm_device *dev)
> > >  	DRM_INFO("applying backlight present quirk\n");
> > >  }
> > >  
> > > +/* Some systems require 300ms extra PPS T12 delay to be added to VBT value */
> > 
> > The comment disagrees with the code. Code uses 800ms explicitly instead of
> > +300 ms.
> > 
> 
> Agree, I will change it to 800ms in the comment.
> 
> 
> > > +static void quirk_increase_t12_delay(struct drm_device *dev)
> > > +{
> > > +	struct drm_i915_private *dev_priv = to_i915(dev);
> > > +
> > > +	dev_priv->quirks |= QUIRK_INCREASE_T12_DELAY;
> > > +	DRM_INFO("Applying T12 delay quirk\n");
> > > +}
> > > +
> > >  struct intel_quirk {
> > >  	int device;
> > >  	int subsystem_vendor;
> > > @@ -14848,6 +14857,9 @@ static struct intel_quirk intel_quirks[] = {
> > >  
> > >  	/* Dell Chromebook 11 (2015 version) */
> > >  	{ 0x0a16, 0x1028, 0x0a35, quirk_backlight_present },
> > > +
> > > +	/* Toshiba Satellite P50-C-18C */
> > > +	{ 0x191B, 0x1179, 0xF840, quirk_increase_t12_delay },
> > 
> > Hmm. Looks like the 1179:f840 combo is present on a lot of Toshiba
> > models. But we do have the device ID here too so the quirk shouldn't
> > go totally overboard.
> >
> 
> Yea this quirk should then get applied only to this device.
> Do you have any other Toshiba laptop with 1179:f840 combo
> to make sure it doesnt get applied on that?

No, but google shows many.

> 
>  
> > >  };
> > >  
> > >  static void intel_init_quirks(struct drm_device *dev)
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > > index 67bc8a7a..db6953e 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -49,6 +49,9 @@
> > >  #define INTEL_DP_RESOLUTION_STANDARD	(2 << INTEL_DP_RESOLUTION_SHIFT_MASK)
> > >  #define INTEL_DP_RESOLUTION_FAILSAFE	(3 << INTEL_DP_RESOLUTION_SHIFT_MASK)
> > >  
> > > +/* PPS T12 Delay Quirk value for eDP */
> > > +#define T11_T12_800MS		8000
> > 
> > The define seems pointless. Just use the raw number in the code. Also
> > writing it as 800*10 would be more consistent with the rest of the code.
> > 
> 
> Sounds good, will use 800*10
> 
> > > +
> > >  struct dp_link_dpll {
> > >  	int clock;
> > >  	struct dpll dpll;
> > > @@ -5230,6 +5233,15 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
> > >  	intel_pps_dump_state("cur", &cur);
> > >  
> > >  	vbt = dev_priv->vbt.edp.pps;
> > > +	/* Apply the QUIRK_INCREASE_T12_DELAY quirk for a specific
> > > +	 * type of PCI device to avoid  DP AUX CH Timeouts.
> > 
> > That comment doesn't seem very helpful. I would put in something like:
> > 
> > "On Toshiba <whatever> the VBT t12 delay of 500ms appears to be too
> >  short. Occasionally the panel just fails to power back on. Increasing
> >  the delay to 800ms seems sufficient to avoid the problem."
> >
> 
> Ok will do
> 
> Manasi
>  
> > > +	 */
> > > +	if (dev_priv->quirks & QUIRK_INCREASE_T12_DELAY) {
> > > +
> > > +		vbt.t11_t12 = max_t(u16, vbt.t11_t12, T11_T12_800MS);
> > > +		DRM_DEBUG_KMS("Increasing T12 panel delay as per the quirk to %d\n",
> > > +			      vbt.t11_t12);
> > > +	}
> > >  	/* T11_T12 delay is special and actually in units of 100ms, but zero
> > >  	 * based in the hw (so we need to add 100 ms). But the sw vbt
> > >  	 * table multiplies it with 1000 to make it in units of 100usec,
> > > -- 
> > > 2.1.4
> > 
> > -- 
> > Ville Syrjälä
> > Intel OTC

-- 
Ville Syrjälä
Intel OTC
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