On 2019-08-26 2:05 p.m., David Francis wrote:
> Synaptics DP1.4 hubs (BRANCH_ID 0x90CC24) do not
> support virtual DPCD registers, but do support DSC.
> The DSC caps can be read from the physical aux,
> like in SST DSC. These hubs have many different
> DEVICE_IDs. Add a new quirk to detect this case.
>
> Cc: Lyude Paul <lyude@xxxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: David Francis <David.Francis@xxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_helper.c | 2 ++
> include/drm/drm_dp_helper.h | 7 +++++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 2cc21eff4cf3..fc39323e7d52 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1270,6 +1270,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
> { 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) },
> + /* 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) },
This seems to be generic OUI for Synaptics [1]. Could this cause us to
cast the net too wide?
Even if we check that it's DP_DPCD_REV >= 1.4 there's a good chance
Synaptics is fixing this in the future and won't require the quirk.
[1] https://aruljohn.com/mac/vendor/Synaptics
Harry
> };
>
> #undef OUI
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 8364502f92cf..a1331b08705f 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1434,6 +1434,13 @@ enum drm_dp_quirk {
> * The driver should ignore SINK_COUNT during detection.
> */
> DP_DPCD_QUIRK_NO_SINK_COUNT,
> + /**
> + * @DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD:
> + *
> + * The device supports MST DSC despite not supporting Virtual DPCD.
> + * The DSC caps can be read from the physical aux instead.
> + */
> + DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
> };
>
> /**
>
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