Re: [Intel-gfx] [PATCH] drm/i915: Add DPCD quirk for AUO PSR2 panel

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 10 Dec 2019, Gaurav K Singh <gaurav.k.singh@intel.com> wrote:
> Currently on AUO PSR2 panel on Gen9 chromebook, we are observing
> below issues:
> (i) The display will show garbage after pressing sign
> out icon in log in screen when wallpaper is one of Solid colors
> & PSR2 is enabled
> (ii) The characters of display is not clear when switch
> OS mode to dev mode.
>
> Before this patch, on this panel, we set idle frame count to 6
> that is number of idle frames before entering PSR2 deep sleep
> and the number of frames to enter into Selective update we set
> to 1.
>
> On this AUO panel, we suspect there is some DP synchronization
> latency needed, due to which we are facing the above issues.
>
> With current TCON of the AUO panel, DPCD reg
> DP_SYNCHRONIZATION_LATENCY_IN_SINK (0x2009) offset is giving a
> value of 0x0.
>
> This patch sets idle frame count to 9 and frame count for selective
> update to 9, after which we are not seeing the above mentioned issues.
>
> Ideally this value needs to be corrected in TCON of the panel
> since this value comes from DPCD reg 0x2009 offset and i915 driver
> uses it. Working with AUO panel vendor to get this fixed in the
> panel TCON. In the meantime fixing this as DPCD quirk in the kernel.
>
> Signed-off-by: Gaurav K Singh <gaurav.k.singh@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c          | 3 +++
>  drivers/gpu/drm/i915/display/intel_psr.c | 6 ++++++
>  include/drm/drm_dp_helper.h              | 9 +++++++++
>  3 files changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 2c7870aef469..96eaeef814d3 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1155,6 +1155,9 @@ struct dpcd_quirk {
>  	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_NO_PSR) },
>  	/* CH7511 seems to leave SINK_COUNT zeroed */
>  	{ OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) },
> +	/* AUO PSR2 panels need some more DP synchronization latency */
> +	{ OUI(0x00, 0x1c, 0xf8), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_SYNCHRONIZATION_LATENCY) },

DEVICE_ID_ANY seems pretty lax.

BR,
Jani.

> +
>  };
>  
>  #undef OUI
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 16e9ff47d519..1023b08ad093 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -296,6 +296,12 @@ void intel_psr_init_dpcd(struct intel_dp *intel_dp)
>  	dev_priv->psr.sink_sync_latency =
>  		intel_dp_get_sink_sync_latency(intel_dp);
>  
> +	if (drm_dp_has_quirk(&intel_dp->desc, DP_DPCD_QUIRK_SYNCHRONIZATION_LATENCY)) {
> +		DRM_DEBUG_KMS("AUO PSR2 panel need more synchronization latency\n");
> +		if (dev_priv->psr.sink_sync_latency == 0)
> +			dev_priv->psr.sink_sync_latency = 8;
> +	}
> +
>  	dev_priv->psr.dp = intel_dp;
>  
>  	if (INTEL_GEN(dev_priv) >= 9 &&
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 8f8f3632e697..6018b79f2d61 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1522,6 +1522,15 @@ enum drm_dp_quirk {
>  	 * The driver should ignore SINK_COUNT during detection.
>  	 */
>  	DP_DPCD_QUIRK_NO_SINK_COUNT,
> +	/**
> +	 * @DP_DPCD_QUIRK_SYNCHRONIZATION_LATENCY
> +	 *
> +	 * The Helios AUO PSR2 panel requires more number of frames on PSR exit,
> +	 * to synchronize to the Source device-provided timing. Currently DPCD
> +	 * 0x2009 offset in TCON has the value of 0. Increasing this value to 8
> +	 * till this gets fixed in TCON of the panel.
> +	 */
> +	DP_DPCD_QUIRK_SYNCHRONIZATION_LATENCY,
>  };
>  
>  /**

-- 
Jani Nikula, Intel Open Source Graphics Center
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