Nouveau - Nov 2020 - [PATCH 0/2] drm/nouveau: Stable backport of DP clock fixes for v5.9

Just a backport of the two patches for v5.9 that you'll want to apply.
The first one was Cc'd to stable, but I forgot to Cc the second one as
well.

Lyude Paul (2):
  drm/nouveau/kms/nv50-: Get rid of bogus nouveau_conn_mode_valid()
  drm/nouveau/kms/nv50-: Fix clock checking algorithm in
    nv50_dp_mode_valid()

 drivers/gpu/drm/nouveau/nouveau_connector.c | 36 ++++++---------------
 drivers/gpu/drm/nouveau/nouveau_dp.c        | 21 ++++++++----
 2 files changed, 24 insertions(+), 33 deletions(-)

-- 
2.28.0

Ville also pointed out that I got a lot of the logic here wrong as well, whoops.
While I don't think anyone's likely using 3D output with nouveau, the
next patch
will make nouveau_conn_mode_valid() make a lot less sense. So, let's just
get
rid of it and open-code it like before, while taking care to move the 3D frame
packing calculations on the dot clock into the right place.

Signed-off-by: Lyude Paul <lyude at redhat.com>
Fixes: d6a9efece724 ("drm/nouveau/kms/nv50-: Share DP SST mode_valid()
handling with MST")
Cc: Ville Syrj?l? <ville.syrjala at linux.intel.com>
Cc: <stable at vger.kernel.org> # v5.8+
Signed-off-by: Ben Skeggs <bskeggs at redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_connector.c | 36 ++++++---------------
 drivers/gpu/drm/nouveau/nouveau_dp.c        | 15 ++++++---
 2 files changed, 20 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
b/drivers/gpu/drm/nouveau/nouveau_connector.c
index 7674025a4bfe8..1d91d52ee5083 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -1035,29 +1035,6 @@ get_tmds_link_bandwidth(struct drm_connector *connector)
 		return 112000 * duallink_scale;
 }
 
-enum drm_mode_status
-nouveau_conn_mode_clock_valid(const struct drm_display_mode *mode,
-			      const unsigned min_clock,
-			      const unsigned max_clock,
-			      unsigned int *clock_out)
-{
-	unsigned int clock = mode->clock;
-
-	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) =-	   
DRM_MODE_FLAG_3D_FRAME_PACKING)
-		clock *= 2;
-
-	if (clock < min_clock)
-		return MODE_CLOCK_LOW;
-	if (clock > max_clock)
-		return MODE_CLOCK_HIGH;
-
-	if (clock_out)
-		*clock_out = clock;
-
-	return MODE_OK;
-}
-
 static enum drm_mode_status
 nouveau_connector_mode_valid(struct drm_connector *connector,
 			     struct drm_display_mode *mode)
@@ -1065,7 +1042,7 @@ nouveau_connector_mode_valid(struct drm_connector
*connector,
 	struct nouveau_connector *nv_connector = nouveau_connector(connector);
 	struct nouveau_encoder *nv_encoder = nv_connector->detected_encoder;
 	struct drm_encoder *encoder = to_drm_encoder(nv_encoder);
-	unsigned min_clock = 25000, max_clock = min_clock;
+	unsigned int min_clock = 25000, max_clock = min_clock, clock = mode->clock;
 
 	switch (nv_encoder->dcb->type) {
 	case DCB_OUTPUT_LVDS:
@@ -1094,8 +1071,15 @@ nouveau_connector_mode_valid(struct drm_connector
*connector,
 		return MODE_BAD;
 	}
 
-	return nouveau_conn_mode_clock_valid(mode, min_clock, max_clock,
-					     NULL);
+	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) ==
DRM_MODE_FLAG_3D_FRAME_PACKING)
+		clock *= 2;
+
+	if (clock < min_clock)
+		return MODE_CLOCK_LOW;
+	if (clock > max_clock)
+		return MODE_CLOCK_HIGH;
+
+	return MODE_OK;
 }
 
 static struct drm_encoder *
diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c
b/drivers/gpu/drm/nouveau/nouveau_dp.c
index 8a0f7994e1aeb..40683e1244c3f 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dp.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
@@ -114,18 +114,23 @@ nv50_dp_mode_valid(struct drm_connector *connector,
 		   unsigned *out_clock)
 {
 	const unsigned min_clock = 25000;
-	unsigned max_clock, clock;
-	enum drm_mode_status ret;
+	unsigned max_clock, clock = mode->clock;
 
 	if (mode->flags & DRM_MODE_FLAG_INTERLACE &&
!outp->caps.dp_interlace)
 		return MODE_NO_INTERLACE;
 
+	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) ==
DRM_MODE_FLAG_3D_FRAME_PACKING)
+		clock *= 2;
+
 	max_clock = outp->dp.link_nr * outp->dp.link_bw;
 	clock = mode->clock * (connector->display_info.bpc * 3) / 10;
+	if (clock < min_clock)
+		return MODE_CLOCK_LOW;
+	if (clock > max_clock)
+		return MODE_CLOCK_HIGH;
 
-	ret = nouveau_conn_mode_clock_valid(mode, min_clock, max_clock,
-					    &clock);
 	if (out_clock)
 		*out_clock = clock;
-	return ret;
+
+	return MODE_OK;
 }
-- 
2.28.0

While I thought I had this correct (since it actually did reject modes
like I expected during testing), Ville Syrjala from Intel pointed out
that the logic here isn't correct. max_clock refers to the max data rate
supported by the DP encoder. So, limiting it to the output of ds_clock (which
refers to the maximum dotclock of the downstream DP device) doesn't make any
sense. Additionally, since we're using the connector's bpc as the
canonical BPC
we should use this in mode_valid until we support dynamically setting the bpp
based on bandwidth constraints.

https://lists.freedesktop.org/archives/dri-devel/2020-September/280276.html

For more info.

So, let's rewrite this using Ville's advice.

Changes made for stable backport:
* 5.9 didn't use drm_dp_downstream_max_dotclock() yet, so remove that (the
  fix is still important regardless)

v2:
* Ville pointed out I mixed up the dotclock and the link rate. So fix that...
* ...and also rename all the variables in this function to be more appropriately
  labeled so I stop mixing them up.
* Reuse the bpp from the connector for now until we have dynamic bpp selection.
* Use use DIV_ROUND_UP for calculating the mode rate like i915 does, which we
  should also have been doing from the start

Signed-off-by: Lyude Paul <lyude at redhat.com>
Fixes: 409d38139b42 ("drm/nouveau/kms/nv50-: Use downstream DP clock limits
for mode validation")
Cc: Ville Syrj?l? <ville.syrjala at linux.intel.com>
Cc: Lyude Paul <lyude at redhat.com>
Cc: Ben Skeggs <bskeggs at redhat.com>
Signed-off-by: Ben Skeggs <bskeggs at redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_dp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c
b/drivers/gpu/drm/nouveau/nouveau_dp.c
index 40683e1244c3f..9c06d1cc43905 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dp.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
@@ -114,7 +114,8 @@ nv50_dp_mode_valid(struct drm_connector *connector,
 		   unsigned *out_clock)
 {
 	const unsigned min_clock = 25000;
-	unsigned max_clock, clock = mode->clock;
+	unsigned int max_rate, mode_rate, clock = mode->clock;
+	const u8 bpp = connector->display_info.bpc * 3;
 
 	if (mode->flags & DRM_MODE_FLAG_INTERLACE &&
!outp->caps.dp_interlace)
 		return MODE_NO_INTERLACE;
@@ -122,12 +123,13 @@ nv50_dp_mode_valid(struct drm_connector *connector,
 	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) ==
DRM_MODE_FLAG_3D_FRAME_PACKING)
 		clock *= 2;
 
-	max_clock = outp->dp.link_nr * outp->dp.link_bw;
-	clock = mode->clock * (connector->display_info.bpc * 3) / 10;
+	max_rate = outp->dp.link_nr * outp->dp.link_bw;
+	mode_rate = DIV_ROUND_UP(clock * bpp, 8);
+	if (mode_rate > max_rate)
+		return MODE_CLOCK_HIGH;
+
 	if (clock < min_clock)
 		return MODE_CLOCK_LOW;
-	if (clock > max_clock)
-		return MODE_CLOCK_HIGH;
 
 	if (out_clock)
 		*out_clock = clock;
-- 
2.28.0

On Fri, Nov 06, 2020 at 06:30:13PM -0500, Lyude Paul
wrote:
> Just a backport of the two patches for v5.9 that you'll want to apply.
> The first one was Cc'd to stable, but I forgot to Cc the second one as
> well.
> 
> Lyude Paul (2):
>   drm/nouveau/kms/nv50-: Get rid of bogus nouveau_conn_mode_valid()
>   drm/nouveau/kms/nv50-: Fix clock checking algorithm in
>     nv50_dp_mode_valid()
> 
>  drivers/gpu/drm/nouveau/nouveau_connector.c | 36 ++++++---------------
>  drivers/gpu/drm/nouveau/nouveau_dp.c        | 21 ++++++++----
>  2 files changed, 24 insertions(+), 33 deletions(-)
Thanks for these, now queued up.

Next time if you could include what the upstream git commmit ids they
are in Linus's tree, that would help, as I have to list them.

thanks,

greg k-h