[PATCH v4 08/30] drm/dp_mst: Add HBLANK expansion quirk for Synaptics MST hubs

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Mon, 2023-10-30 at 17:58 +0200, Imre Deak wrote:
> Add a quirk for Synaptics MST hubs, which require a workaround - at leat
> on i915 - for some modes, on which the hub applies HBLANK expansion.
> These modes will only work by enabling DSC decompression for them, a
> follow-up patch will do this in i915.
> 
> v2:
> - Fix the quirk name in its DocBook description.
> 
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: dri-devel at lists.freedesktop.org
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 2 ++
>  include/drm/display/drm_dp_helper.h     | 7 +++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index f3680f4e69708..e5d7970a9ddd0 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -2245,6 +2245,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
>  	{ OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) },
>  	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
>  	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
> +	/* Synaptics DP1.4 MST hubs require DSC for some modes on which it applies HBLANK expansion. */
> +	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC) },
>  	/* Apple MacBookPro 2017 15 inch eDP Retina panel reports too low DP_MAX_LINK_RATE */
>  	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID(101, 68, 21, 101, 98, 97), false, BIT(DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS) },
>  };
> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> index 3d74b2cec72fd..da94932f4262b 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -632,6 +632,13 @@ enum drm_dp_quirk {
>  	 * the DP_MAX_LINK_RATE register reporting a lower max multiplier.
>  	 */
>  	DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS,
> +	/**
> +	 * @DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC:
> +	 *
> +	 * The device applies HBLANK expansion for some modes, but this
> +	 * requires enabling DSC.
> +	 */
> +	DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC,
>  };
>  
>  /**

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat