FAILED: patch "[PATCH] drm/amd/display: Reduce accessing remote DPCD overhead" failed to apply to 6.12-stable tree

PATCH In review [email protected] 4 participants 5 messages Jan 20, 2025 – Feb 4, 2025

Subsystems (4)

Stable branch DRM drivers Radeon and amdgpu DRM drivers AMD display core

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[email protected]

author maintainer

2025-01-20 14:18 UTC #0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x adb4998f4928a17d91be054218a902ba9f8c1f93
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025012032-phoenix-crushing-da7a@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From adb4998f4928a17d91be054218a902ba9f8c1f93 Mon Sep 17 00:00:00 2001
From: Wayne Lin <[email protected]>
Date: Mon, 9 Dec 2024 15:25:35 +0800
Subject: [PATCH] drm/amd/display: Reduce accessing remote DPCD overhead

[Why]
Observed frame rate get dropped by tool like glxgear. Even though the output to monitor is 60Hz, the rendered frame rate drops to 30Hz lower.

It's due to code path in some cases will trigger dm_dp_mst_is_port_support_mode() to read out remote Link status to assess the available bandwidth for dsc maniplation. Overhead of keep reading remote DPCD is considerable.

[How]
Store the remote link BW in mst_local_bw and use end-to-end full_pbn as an indicator to decide whether update the remote link bw or not.

Whenever we need the info to assess the BW, visit the stored one first.

Closes https://gitlab.freedesktop.org/drm/amd/-/issues/3720

Fixes fa57924c76d9 ("drm/amd/display: Refactor function dm_dp_mst_is_port_support_mode()")

Cc Mario Limonciello <[email protected]>

Cc Alex Deucher <[email protected]>

Reviewed-by Jerry Zuo <[email protected]>

Signed-off-by Wayne Lin <[email protected]>

Signed-off-by Tom Chung <[email protected]>

Tested-by Daniel Wheeler <[email protected]>

Signed-off-by Alex Deucher <[email protected]>

(cherry picked from commit 4a9a918545455a5979c6232fcf61ed3d8f0db3ae)

Cc [email protected]

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h +2 -0

index 6464a8378387..2227cd8e4a89 100644
@@ -697,6 +697,8 @@ struct amdgpu_dm_connector {
 	struct drm_dp_mst_port *mst_output_port;
 	struct amdgpu_dm_connector *mst_root;
 	struct drm_dp_aux *dsc_aux;
+	uint32_t mst_local_bw;
+	uint16_t vc_full_pbn;
 	struct mutex handle_mst_msg_ready;
 
 	/* TODO see if we can merge with ddc_bus or make a dm_connector */

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c +25 -9

index aadaa61ac5ac..1080075ccb17 100644
@@ -155,6 +155,17 @@ amdgpu_dm_mst_connector_late_register(struct drm_connector *connector)
 	return 0;
 }
 
+
+static inline void
+amdgpu_dm_mst_reset_mst_connector_setting(struct amdgpu_dm_connector *aconnector)
+{
+	aconnector->drm_edid = NULL;
+	aconnector->dsc_aux = NULL;
+	aconnector->mst_output_port->passthrough_aux = NULL;
+	aconnector->mst_local_bw = 0;
+	aconnector->vc_full_pbn = 0;
+}
+
 static void
 amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 {

@@ -182,9 +193,7 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 
 		dc_sink_release(dc_sink);
 		aconnector->dc_sink = NULL;
-		aconnector->drm_edid = NULL;
-		aconnector->dsc_aux = NULL;
-		port->passthrough_aux = NULL;
+		amdgpu_dm_mst_reset_mst_connector_setting(aconnector);
 	}
 
 	aconnector->mst_status = MST_STATUS_DEFAULT;

@@ -504,9 +513,7 @@ dm_dp_mst_detect(struct drm_connector *connector,
 
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
-		aconnector->drm_edid = NULL;
-		aconnector->dsc_aux = NULL;
-		port->passthrough_aux = NULL;
+		amdgpu_dm_mst_reset_mst_connector_setting(aconnector);
 
 		amdgpu_dm_set_mst_status(&aconnector->mst_status,
 			MST_REMOTE_EDID | MST_ALLOCATE_NEW_PAYLOAD | MST_CLEAR_ALLOCATED_PAYLOAD,

@@ -1819,9 +1826,18 @@ enum dc_status dm_dp_mst_is_port_support_mode(
 			struct drm_dp_mst_port *immediate_upstream_port = NULL;
 			uint32_t end_link_bw = 0;
 
-			/*Get last DP link BW capability*/
-			if (dp_get_link_current_set_bw(&aconnector->mst_output_port->aux, &end_link_bw)) {
-				if (stream_kbps > end_link_bw) {
+			/*Get last DP link BW capability. Mode shall be supported by Legacy peer*/
+			if (aconnector->mst_output_port->pdt != DP_PEER_DEVICE_DP_LEGACY_CONV &&
+				aconnector->mst_output_port->pdt != DP_PEER_DEVICE_NONE) {
+				if (aconnector->vc_full_pbn != aconnector->mst_output_port->full_pbn) {
+					dp_get_link_current_set_bw(&aconnector->mst_output_port->aux, &end_link_bw);
+					aconnector->vc_full_pbn = aconnector->mst_output_port->full_pbn;
+					aconnector->mst_local_bw = end_link_bw;
+				} else {
+					end_link_bw = aconnector->mst_local_bw;
+				}
+
+				if (end_link_bw > 0 && stream_kbps > end_link_bw) {
 					DRM_DEBUG_DRIVER("MST_DSC dsc decode at last link."
 							 "Mode required bw can't fit into last link\n");
 					return DC_FAIL_BANDWIDTH_VALIDATE;

Wayne Lin

2025-02-04 10:13 UTC #1 lore raw

PATCH 1/1 drm/amd/display: Reduce accessing remote DPCD overhead

[Why]
Observed frame rate get dropped by tool like glxgear. Even though the output to monitor is 60Hz, the rendered frame rate drops to 30Hz lower.

[How]
Store the remote link BW in mst_local_bw and use end-to-end full_pbn as an indicator to decide whether update the remote link bw or not.

Whenever we need the info to assess the BW, visit the stored one first.

Closes https://gitlab.freedesktop.org/drm/amd/-/issues/3720

Fixes fa57924c76d9 ("drm/amd/display: Refactor function dm_dp_mst_is_port_support_mode()")

Cc Mario Limonciello <[email protected]>

Cc Alex Deucher <[email protected]>

Reviewed-by Jerry Zuo <[email protected]>

Signed-off-by Wayne Lin <[email protected]>

Signed-off-by Tom Chung <[email protected]>

Tested-by Daniel Wheeler <[email protected]>

Signed-off-by Alex Deucher <[email protected]>

(cherry picked from commit 4a9a918545455a5979c6232fcf61ed3d8f0db3ae)

Cc [email protected]

(cherry picked from commit adb4998f4928a17d91be054218a902ba9f8c1f93)

Signed-off-by Wayne Lin <[email protected]>

---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |  2 ++
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 34 ++++++++++++++-----
 2 files changed, 27 insertions(+), 9 deletions(-)

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h +2 -0

index a0bc2c0ac04d..20ad72d1b0d9 100644
@@ -697,6 +697,8 @@ struct amdgpu_dm_connector {
 	struct drm_dp_mst_port *mst_output_port;
 	struct amdgpu_dm_connector *mst_root;
 	struct drm_dp_aux *dsc_aux;
+	uint32_t mst_local_bw;
+	uint16_t vc_full_pbn;
 	struct mutex handle_mst_msg_ready;
 
 	/* TODO see if we can merge with ddc_bus or make a dm_connector */

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c +25 -9

index 3d624ae6d9bd..754dbc544f03 100644
@@ -155,6 +155,17 @@ amdgpu_dm_mst_connector_late_register(struct drm_connector *connector)
 	return 0;
 }
 
+
+static inline void
+amdgpu_dm_mst_reset_mst_connector_setting(struct amdgpu_dm_connector *aconnector)
+{
+	aconnector->edid = NULL;
+	aconnector->dsc_aux = NULL;
+	aconnector->mst_output_port->passthrough_aux = NULL;
+	aconnector->mst_local_bw = 0;
+	aconnector->vc_full_pbn = 0;
+}
+
 static void
 amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 {

@@ -182,9 +193,7 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 
 		dc_sink_release(dc_sink);
 		aconnector->dc_sink = NULL;
-		aconnector->edid = NULL;
-		aconnector->dsc_aux = NULL;
-		port->passthrough_aux = NULL;
+		amdgpu_dm_mst_reset_mst_connector_setting(aconnector);
 	}
 
 	aconnector->mst_status = MST_STATUS_DEFAULT;

@@ -500,9 +509,7 @@ dm_dp_mst_detect(struct drm_connector *connector,
 
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
-		aconnector->edid = NULL;
-		aconnector->dsc_aux = NULL;
-		port->passthrough_aux = NULL;
+		amdgpu_dm_mst_reset_mst_connector_setting(aconnector);
 
 		amdgpu_dm_set_mst_status(&aconnector->mst_status,
 			MST_REMOTE_EDID | MST_ALLOCATE_NEW_PAYLOAD | MST_CLEAR_ALLOCATED_PAYLOAD,

@@ -1815,9 +1822,18 @@ enum dc_status dm_dp_mst_is_port_support_mode(
 			struct drm_dp_mst_port *immediate_upstream_port = NULL;
 			uint32_t end_link_bw = 0;
 
-			/*Get last DP link BW capability*/
-			if (dp_get_link_current_set_bw(&aconnector->mst_output_port->aux, &end_link_bw)) {
-				if (stream_kbps > end_link_bw) {
+			/*Get last DP link BW capability. Mode shall be supported by Legacy peer*/
+			if (aconnector->mst_output_port->pdt != DP_PEER_DEVICE_DP_LEGACY_CONV &&
+				aconnector->mst_output_port->pdt != DP_PEER_DEVICE_NONE) {
+				if (aconnector->vc_full_pbn != aconnector->mst_output_port->full_pbn) {
+					dp_get_link_current_set_bw(&aconnector->mst_output_port->aux, &end_link_bw);
+					aconnector->vc_full_pbn = aconnector->mst_output_port->full_pbn;
+					aconnector->mst_local_bw = end_link_bw;
+				} else {
+					end_link_bw = aconnector->mst_local_bw;
+				}
+
+				if (end_link_bw > 0 && stream_kbps > end_link_bw) {
 					DRM_DEBUG_DRIVER("MST_DSC dsc decode at last link."
 							 "Mode required bw can't fit into last link\n");
 					return DC_FAIL_BANDWIDTH_VALIDATE;

Signature · 1 line

2.37.3

Greg KH

author maintainer

2025-02-04 10:22 UTC #2 lore raw

Re: [PATCH 6.12.y] drm/amd/display: Reduce accessing remote DPCD overhead

Quoted 15 lines · Wayne Lin

[Why]
Observed frame rate get dropped by tool like glxgear. Even though the output to monitor is 60Hz, the rendered frame rate drops to 30Hz lower.
It's due to code path in some cases will trigger dm_dp_mst_is_port_support_mode() to read out remote Link status to assess the available bandwidth for dsc maniplation. Overhead of keep reading remote DPCD is considerable.
[How]
Store the remote link BW in mst_local_bw and use end-to-end full_pbn as an indicator to decide whether update the remote link bw or not.
Whenever we need the info to assess the BW, visit the stored one first.

Quoted 12 lines

Closes https://gitlab.freedesktop.org/drm/amd/-/issues/3720
Fixes fa57924c76d9 ("drm/amd/display: Refactor function dm_dp_mst_is_port_support_mode()")
Cc Mario Limonciello <[email protected]>
Cc Alex Deucher <[email protected]>
Reviewed-by Jerry Zuo <[email protected]>
Signed-off-by Wayne Lin <[email protected]>
Signed-off-by Tom Chung <[email protected]>
Tested-by Daniel Wheeler <[email protected]>
Signed-off-by Alex Deucher <[email protected]>
(cherry picked from commit 4a9a918545455a5979c6232fcf61ed3d8f0db3ae)
Cc [email protected]
(cherry picked from commit adb4998f4928a17d91be054218a902ba9f8c1f93)

I'm confused, which commit is this exactly? Both of these seem to be the same, and you can't have 2 "cherry picked from" lines in a commit, right?

thanks,

greg k-h

Mario Limonciello

2025-02-04 15:09 UTC #3 lore raw

Re: [PATCH 6.12.y] drm/amd/display: Reduce accessing remote DPCD overhead

Quoted 29 lines · Greg KH

Quoted 15 lines · Wayne Lin
[Why]
Observed frame rate get dropped by tool like glxgear. Even though the output to monitor is 60Hz, the rendered frame rate drops to 30Hz lower.
It's due to code path in some cases will trigger dm_dp_mst_is_port_support_mode() to read out remote Link status to assess the available bandwidth for dsc maniplation. Overhead of keep reading remote DPCD is considerable.
[How]
Store the remote link BW in mst_local_bw and use end-to-end full_pbn as an indicator to decide whether update the remote link bw or not.
Whenever we need the info to assess the BW, visit the stored one first.
Quoted 12 lines
Closes https://gitlab.freedesktop.org/drm/amd/-/issues/3720
Fixes fa57924c76d9 ("drm/amd/display: Refactor function dm_dp_mst_is_port_support_mode()")
Cc Mario Limonciello <[email protected]>
Cc Alex Deucher <[email protected]>
Reviewed-by Jerry Zuo <[email protected]>
Signed-off-by Wayne Lin <[email protected]>
Signed-off-by Tom Chung <[email protected]>
Tested-by Daniel Wheeler <[email protected]>
Signed-off-by Alex Deucher <[email protected]>
(cherry picked from commit 4a9a918545455a5979c6232fcf61ed3d8f0db3ae)
Cc [email protected]
(cherry picked from commit adb4998f4928a17d91be054218a902ba9f8c1f93)

Quoted 7 lines

I'm confused, which commit is this exactly? Both of these seem to be the same, and you can't have 2 "cherry picked from" lines in a commit, right?
thanks,
greg k-h

AFAICT what happened here is that this was a case that the same commit landed in 6.13 final as well as 6.14-rc1. So when this was sent this out it was cherry picked from adb4998f4928a17d91be054218a902ba9f8c1f93 which happens to already have a cherry-picked from line from 4a9a918545455a5979c6232fcf61ed3d8f0db3ae.

❯ git describe --contains adb4998f4928a17d91be054218a902ba9f8c1f93 v6.13~16^2~2^2~12

❯ git describe --contains 4a9a918545455a5979c6232fcf61ed3d8f0db3ae v6.14-rc1~174^2~2^2~16

But it looks like you've got it sorted out as I saw it get added to the 6.12 queue.

Sasha Levin

maintainer

2025-02-04 16:34 UTC #4 lore raw

Re: [PATCH 6.12.y] drm/amd/display: Reduce accessing remote DPCD overhead

In reply to Wayne Lin

[ Sasha's backport helper bot ]

Hi,

Found matching upstream commit: adb4998f4928a17d91be054218a902ba9f8c1f93

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Not found

Note: The patch differs from the upstream commit:
---
1: adb4998f4928a ! 1: 0e5ffb81ed4e1 drm/amd/display: Reduce accessing remote DPCD overhead

    @@ Commit message
         Signed-off-by: Alex Deucher <[email protected]>
         (cherry picked from commit 4a9a918545455a5979c6232fcf61ed3d8f0db3ae)
         Cc: [email protected]
    +    (cherry picked from commit adb4998f4928a17d91be054218a902ba9f8c1f93)
    +    Signed-off-by: Wayne Lin <[email protected]>
     
      ## drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h ##
     @@ drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h: struct amdgpu_dm_connector {
    @@ drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c: amdgpu_dm_mst_conne
     +static inline void
     +amdgpu_dm_mst_reset_mst_connector_setting(struct amdgpu_dm_connector *aconnector)
     +{
    -+	aconnector->drm_edid = NULL;
    ++	aconnector->edid = NULL;
     +	aconnector->dsc_aux = NULL;
     +	aconnector->mst_output_port->passthrough_aux = NULL;
     +	aconnector->mst_local_bw = 0;
    @@ drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c: amdgpu_dm_mst_conne
      
      		dc_sink_release(dc_sink);
      		aconnector->dc_sink = NULL;
    --		aconnector->drm_edid = NULL;
    +-		aconnector->edid = NULL;
     -		aconnector->dsc_aux = NULL;
     -		port->passthrough_aux = NULL;
     +		amdgpu_dm_mst_reset_mst_connector_setting(aconnector);
    @@ drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c: dm_dp_mst_detect(st
      
      		dc_sink_release(aconnector->dc_sink);
      		aconnector->dc_sink = NULL;
    --		aconnector->drm_edid = NULL;
    +-		aconnector->edid = NULL;
     -		aconnector->dsc_aux = NULL;
     -		port->passthrough_aux = NULL;
     +		amdgpu_dm_mst_reset_mst_connector_setting(aconnector);

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Success    |  Success   |