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

[Clint Taylor <clinton.a.taylor@intel.com>]

On 06/08/2018 06:31 AM, Imre Deak wrote:
> Hi Clint,
>
> nice debugging!
>
> On Thu, Jun 07, 2018 at 04:12:39PM -0700, clinton.a.taylor@intel.com wrote:
>> From: Clint Taylor <clinton.a.taylor@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.
If switching from 30Hz to 50/60Hz you would only need a delay of 34ms, 
but I chose to keep the quirk simple and use the worst case (23.98Hz) 
delay of 42ms.
>
> 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?
Just an off/on mode set with enough delay will bring the chip out of the 
bad state.

-Clint
>
> --Imre
>
>> Cc: Imre Deak <imre.deak@intel.com>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105887
>> Signed-off-by: Clint Taylor <clinton.a.taylor@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
>>

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