[Intel-gfx] [PATCH] drm/i915/glk: Add Quirk for GLK NUC HDMI port issues.

[Imre Deak]

Hi Clint,

nice debugging!

On Thu, Jun 07, 2018 at 04:12:39PM -0700, clinton.a.taylor at intel.com wrote:
> From: Clint Taylor <clinton.a.taylor at intel.com>
> 
> On GLK NUC platforms the HDMI retiming buffer needs additional disabled
> time to correctly sync to a faster incoming signal.
> When measured on a scope the highspeed lines of the HDMI clock turn
> off for ~400uS during a normal resolution change.  The HDMI retimer on
> the GLK NUC appears to require at least a full frame of quiet time
> before a new faster clock can be correctly sync'd.
> The worst case scenario appears to be 23.98Hz modes which requires a
> wait of 41.25ms. Add a quirk to the driver for GLK NUC that waits
> 42ms.

Just to understand better the failure mode: IIUC without the WA the HDMI
clock line is inactive for ~400us when switching modes (which would
depend on kernel timing) and the retimer chip needs at least 42ms idle
time at least when switching to certain modes.

Is there a way to recover the chip from the bad state? By doing a new
off/on modeset with enough idle time, or resetting the chip?

--Imre

> 
> Cc: Imre Deak <imre.deak at intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105887
> Signed-off-by: Clint Taylor <clinton.a.taylor at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      |  1 +
>  drivers/gpu/drm/i915/intel_ddi.c     |  8 ++++++++
>  drivers/gpu/drm/i915/intel_display.c | 14 ++++++++++++++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index c407366..628491d 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -645,6 +645,7 @@ enum intel_sbi_destination {
>  #define QUIRK_BACKLIGHT_PRESENT (1<<3)
>  #define QUIRK_PIN_SWIZZLED_PAGES (1<<5)
>  #define QUIRK_INCREASE_T12_DELAY (1<<6)
> +#define QUIRK_INCREASE_DDI_DISABLED_TIME (1<<7)
>  
>  struct intel_fbdev;
>  struct intel_fbc_work;
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index b344e0f..61b41c3 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1784,6 +1784,9 @@ void intel_ddi_enable_transcoder_func(const struct intel_crtc_state *crtc_state)
>  	I915_WRITE(TRANS_DDI_FUNC_CTL(cpu_transcoder), temp);
>  }
>  
> +/* Quirk time computed based on 24fps frame time of 41.25ms */
> +#define DDI_DISABLED_QUIRK_TIME 42
> +
>  void intel_ddi_disable_transcoder_func(struct drm_i915_private *dev_priv,
>  				       enum transcoder cpu_transcoder)
>  {
> @@ -1793,6 +1796,11 @@ void intel_ddi_disable_transcoder_func(struct drm_i915_private *dev_priv,
>  	val &= ~(TRANS_DDI_FUNC_ENABLE | TRANS_DDI_PORT_MASK | TRANS_DDI_DP_VC_PAYLOAD_ALLOC);
>  	val |= TRANS_DDI_PORT_NONE;
>  	I915_WRITE(reg, val);
> +
> +	if (dev_priv->quirks & QUIRK_INCREASE_DDI_DISABLED_TIME) {
> +		msleep(DDI_DISABLED_QUIRK_TIME);
> +		DRM_DEBUG_KMS("Quirk Increase DDI disabled time\n");
> +	}
>  }
>  
>  int intel_ddi_toggle_hdcp_signalling(struct intel_encoder *intel_encoder,
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index ed29219..0d07c37 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14740,6 +14740,17 @@ static void quirk_increase_t12_delay(struct drm_device *dev)
>  	DRM_INFO("Applying T12 delay quirk\n");
>  }
>  
> +/* GeminiLake NUC HDMI outputs require additional off time
> + * this allows the onboard retimer to correctly sync to signal
> + */
> +static void quirk_increase_ddi_disabled_time(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +
> +	dev_priv->quirks |= QUIRK_INCREASE_DDI_DISABLED_TIME;
> +	DRM_INFO("Applying Increase DDI Disabled quirk\n");
> +}
> +
>  struct intel_quirk {
>  	int device;
>  	int subsystem_vendor;
> @@ -14826,6 +14837,9 @@ static int intel_dmi_reverse_brightness(const struct dmi_system_id *id)
>  
>  	/* Toshiba Satellite P50-C-18C */
>  	{ 0x191B, 0x1179, 0xF840, quirk_increase_t12_delay },
> +
> +	/* GeminiLake NUC */
> +	{ 0x3185, 0x8086, 0x2072, quirk_increase_ddi_disabled_time },
>  };
>  
>  static void intel_init_quirks(struct drm_device *dev)
> -- 
> 1.9.1
>