Re: [PATCH 12/19] drm/i915/dp: Add member to intel_dp to store AS SDP v2 support

Nautiyal, Ankit K
2026-03-31T11:50:11Z

On 3/30/2026 11:59 PM, Ville Syrjälä wrote:
> On Mon, Mar 30, 2026 at 09:36:49AM +0530, Ankit Nautiyal wrote:
>> DP v2.1 SCR advertises support for FAVT payload fields parsing in DPCD
>> 0x2214 Bit 2. This indicates the support for Adaptive-Sync SDP version 2
>> (AS SDP v2), which allows the source to set the version in HB2[4:0] and the
>> payload length in HB3[5:0] of the AS SDP header.
>>
>> DP v2.1 SCR also adds a bit for Async Video Timing during Panel Replay, in
>> Panel Replay Capability DPCD 0x00b1 (Bit 3). When this bit is cleared, the
>> sink supports asynchronous video timing while in a Panel Replay Active
>> state. The spec mandates that such sinks shall support AS SDP v2.
>>
>> Infer AS SDP v2 support from these capabilities and store it in
>> struct intel_dp for use by subsequent feature enablement changes.
>>
>> v2:
>> - Include parsing ASYNC_VIDEO_TIMING_NOT_SUPPORTED_IN_PR bit to
>> determine AS SDP v2 support. (Ville)
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> ---
>> .../drm/i915/display/intel_display_types.h | 1 +
>> drivers/gpu/drm/i915/display/intel_dp.c | 37 +++++++++++++++++++
>> 2 files changed, 38 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
>> index e2496db1642a..efc609eef4f5 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> @@ -1870,6 +1870,7 @@ struct intel_dp {
>> /* connector directly attached - won't be use for modeset in mst world */
>> struct intel_connector *attached_connector;
>> bool as_sdp_supported;
>> + bool as_sdp_v2_supported;
>>
>> struct drm_dp_tunnel *tunnel;
>> bool tunnel_suspended:1;
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index f9bfb07f0205..b2007ffe18bc 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -6301,6 +6301,40 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
>> false);
>> }
>>
>> +static bool
>> +intel_dp_sink_supports_as_sdp_v2(struct intel_dp *intel_dp)
>> +{
>> + u8 rx_features;
>> + u8 pr_caps;
>> +
>> + /*
>> + * The DP spec does not explicitly provide the AS SDP v2 capability.
>> + * So based on the DP v2.1 SCR, we infer it from the following bits:
>> + *
>> + * DP_AS_SDP_FAVT_PAYLOAD_FIELDS_PARSING_SUPPORTED indicates support for
>> + * FAVT, which is explicitly defined to use AS SDP v2.
>> + *
>> + * DP_ASYNC_VIDEO_TIMING_NOT_SUPPORTED_IN_PR cleared indicates support
>> + * for Async Video timing in PR active and the spec mandates that such
>> + * sinks shall support AS SDP v2.
>> + */
>> + if (drm_dp_dpcd_read_byte(&intel_dp->aux,
>> + DP_DPRX_FEATURE_ENUMERATION_LIST_CONT_1,
>> + &rx_features) == 1) {
>> + if (rx_features & DP_AS_SDP_FAVT_PAYLOAD_FIELDS_PARSING_SUPPORTED)
>> + return true;
>> + }
>> +
>> + if (drm_dp_dpcd_read_byte(&intel_dp->aux,
>> + DP_PANEL_REPLAY_CAP_CAPABILITY,
>> + &pr_caps) == 1) {
>> + if (!(pr_caps & DP_PANEL_REPLAY_ASYNC_VIDEO_TIMING_NOT_SUPPORTED_IN_PR))
> That seems to be backwards. If the sink requires AS SDP
> then it will set the bit.

Hmm.. I indeed got it backwards, you are right.

If Async Video timing is supported then re-set the bit. But in that case
AS SDP is not required.

So reset means AS SDP not required; bit set means it is required.

Thanks, I will correct this in next version.

Regards,

Ankit

>
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>> +
>> static void
>> intel_dp_detect_sdp_caps(struct intel_dp *intel_dp)
>> {
>> @@ -6308,6 +6342,9 @@ intel_dp_detect_sdp_caps(struct intel_dp *intel_dp)
>>
>> intel_dp->as_sdp_supported = HAS_AS_SDP(display) &&
>> drm_dp_as_sdp_supported(&intel_dp->aux, intel_dp->dpcd);
>> +
>> + intel_dp->as_sdp_v2_supported = intel_dp->as_sdp_supported &&
>> + intel_dp_sink_supports_as_sdp_v2(intel_dp);
>> }
>>
>> static bool intel_dp_needs_dpcd_probe(struct intel_dp *intel_dp, bool force_on_external)
>> --
>> 2.45.2