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James Jones

2025-Oct-30 18:11 UTC

[PATCH v2 0/2] drm/nouveau: Advertise correct modifiers on GB20x

This series adds new format modifiers for 8 and 16-bit formats on GB20x
GPUs, preventing them from mistakenly sharing block-linear surfaces
using these formats with prior GPUs that use a different layout.

There are a few ways the parameteric format modifier definition
could have been altered to handle the new layouts:

-The GOB Height and Page Kind field has a reserved value that could
 have been used. However, the GOB height and page kind enums did
 not change relative to prior chips, so this is sort of a lie.
 However, this is the least-invasive change.

-An entirely new field could have been added. This seems
 inappropriate given the presence of an existing appropriate field.
 The advantage here is it avoids splitting the sector layout field
 across two bitfields.

The chosen approach is the logically consistent one, but has the
downside of being the most complex, and that it causes the
DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D() macro to evaluate its 's'
parameter twice. However, utilizing simple helper functions in
client code when accessing the parameteric format modifier fields
easily addresses the complexity, and I have audited the relevant code
and do not believe the double evaluation should cause any problems in
practice.

Tested on GB20x and TU10x cards using the following:

-kmscube w/NVK+Zink built with these patches applied:

   https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36336

 with various manually specified formats
 and both manually specified and automatically
 selected modifiers.

-drmfmtmods, a tiny test program that lists modifiers:

   https://github.com/cubanismo/drmfmtmods

Changes in v2:

-Added "Fixes: 6cc6e08d4542" line since this can be considered a bug
 fix for the initial blackwell KMS support in nouveau.

-Dropped the second patch from the v1 series as it has been merged.

Changes since the RFC version here:

  https://lore.kernel.org/nouveau/20250703223658.1457-1-jajones at nvidia.com/

-Dropped the helper macros & static inlines in
 drm_fourcc.h as requested by Faith Ekstrand,
 who noted these aren't helpful for UMD code,
 which is all written in rust now. I may re-
 introduce some of these in a subsequent series,
 but we both agreed we do not want to delay
 progress on the modifiers themselves while we
 debate the details of those cometic details.

-Reserved an extra bit for future sector
 layouts.

-Fixed handling of linear modifiers on GB20x
 and NV5x/G8x/G9x/GT2xx chips.

James Jones (2):
  drm: define NVIDIA DRM format modifiers for GB20x
  drm/nouveau: Advertise correct modifiers on GB20x

 drivers/gpu/drm/nouveau/dispnv50/disp.c     |  4 ++-
 drivers/gpu/drm/nouveau/dispnv50/disp.h     |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndw.c     | 24 +++++++++++++--
 drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c | 33 +++++++++++++++++++++
 include/uapi/drm/drm_fourcc.h               | 25 ++++++++++------
 5 files changed, 75 insertions(+), 12 deletions(-)

-- 
2.50.1

James Jones

2025-Oct-30 18:11 UTC

head link

[PATCH v2 1/2] drm: define NVIDIA DRM format modifiers for GB20x

The layout of bits within the individual tiles
(referred to as sectors in the
DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D() macro)
changed for 8 and 16-bit surfaces starting in
Blackwell 2 GPUs (With the exception of GB10).
To denote the difference, extend the sector field
in the parametric format modifier definition used
to generate modifier values for NVIDIA hardware.

Without this change, it would be impossible to
differentiate the two layouts based on modifiers,
and as a result software could attempt to share
surfaces directly between pre-GB20x and GB20x
cards, resulting in corruption when the surface
was accessed on one of the GPUs after being
populated with content by the other.

Of note: This change causes the
DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D() macro to
evaluate its "s" parameter twice, with the side
effects that entails. I surveyed all usage of the
modifier in the kernel and Mesa code, and that
does not appear to be problematic in any current
usage, but I thought it was worth calling out.

Fixes: 6cc6e08d4542 ("drm/nouveau/kms: add support for GB20x")
Signed-off-by: James Jones <jajones at nvidia.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand at collabora.com>
---

(no changes since v1)

 include/uapi/drm/drm_fourcc.h | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index ea91aa8afde9..e527b24bd824 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h
@@ -979,14 +979,20 @@ extern "C" {
  *               2 = Gob Height 8, Turing+ Page Kind mapping
  *               3 = Reserved for future use.
  *
- * 22:22 s     Sector layout.  On Tegra GPUs prior to Xavier, there is a
further
- *             bit remapping step that occurs at an even lower level than the
- *             page kind and block linear swizzles.  This causes the layout of
- *             surfaces mapped in those SOC's GPUs to be incompatible with
the
- *             equivalent mapping on other GPUs in the same system.
- *
- *               0 = Tegra K1 - Tegra Parker/TX2 Layout.
- *               1 = Desktop GPU and Tegra Xavier+ Layout
+ * 22:22 s     Sector layout.  There is a further bit remapping step that
occurs
+ * 26:27       at an even lower level than the page kind and block linear
+ *             swizzles.  This causes the bit arrangement of surfaces in memory
+ *             to differ subtly, and prevents direct sharing of surfaces
between
+ *             GPUs with different layouts.
+ *
+ *               0 = Tegra K1 - Tegra Parker/TX2 Layout
+ *               1 = Pre-GB20x, GB20x 32+ bpp, GB10, Tegra Xavier-Orin Layout
+ *               2 = GB20x(Blackwell 2)+ 8 bpp surface layout
+ *               3 = GB20x(Blackwell 2)+ 16 bpp surface layout
+ *               4 = Reserved for future use.
+ *               5 = Reserved for future use.
+ *               6 = Reserved for future use.
+ *               7 = Reserved for future use.
  *
  * 25:23 c     Lossless Framebuffer Compression type.
  *
@@ -1001,7 +1007,7 @@ extern "C" {
  *               6 = Reserved for future use
  *               7 = Reserved for future use
  *
- * 55:25 -     Reserved for future use.  Must be zero.
+ * 55:28 -     Reserved for future use.  Must be zero.
  */
 #define DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(c, s, g, k, h) \
 	fourcc_mod_code(NVIDIA, (0x10 | \
@@ -1009,6 +1015,7 @@ extern "C" {
 				 (((k) & 0xff) << 12) | \
 				 (((g) & 0x3) << 20) | \
 				 (((s) & 0x1) << 22) | \
+				 (((s) & 0x6) << 25) | \
 				 (((c) & 0x7) << 23)))
 
 /* To grandfather in prior block linear format modifiers to the above layout,
-- 
2.50.1

James Jones

2025-Oct-30 18:11 UTC

head link

[PATCH v2 2/2] drm/nouveau: Advertise correct modifiers on GB20x

8 and 16 bit formats use a different layout on
GB20x than they did on prior chips. Add the
corresponding DRM format modifiers to the list of
modifiers supported by the display engine on such
chips, and filter the supported modifiers for each
format based on its bytes per pixel in
nv50_plane_format_mod_supported().

Note this logic will need to be updated when GB10
support is added, since it is a GB20x chip that
uses the pre-GB20x sector layout for all formats.

Fixes: 6cc6e08d4542 ("drm/nouveau/kms: add support for GB20x")
Signed-off-by: James Jones <jajones at nvidia.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand at collabora.com>
---

(no changes since v1)

 drivers/gpu/drm/nouveau/dispnv50/disp.c     |  4 ++-
 drivers/gpu/drm/nouveau/dispnv50/disp.h     |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndw.c     | 24 +++++++++++++--
 drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c | 33 +++++++++++++++++++++
 4 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c
b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index e97e39abf3a2..12b1dba8e05d 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -2867,7 +2867,9 @@ nv50_display_create(struct drm_device *dev)
 	}
 
 	/* Assign the correct format modifiers */
-	if (disp->disp->object.oclass >= TU102_DISP)
+	if (disp->disp->object.oclass >= GB202_DISP)
+		nouveau_display(dev)->format_modifiers = wndwca7e_modifiers;
+	else if (disp->disp->object.oclass >= TU102_DISP)
 		nouveau_display(dev)->format_modifiers = wndwc57e_modifiers;
 	else
 	if (drm->client.device.info.family >= NV_DEVICE_INFO_V0_FERMI)
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.h
b/drivers/gpu/drm/nouveau/dispnv50/disp.h
index 15f9242b72ac..5d998f0319dc 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.h
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.h
@@ -104,4 +104,5 @@ struct nouveau_encoder *nv50_real_outp(struct drm_encoder
*encoder);
 extern const u64 disp50xx_modifiers[];
 extern const u64 disp90xx_modifiers[];
 extern const u64 wndwc57e_modifiers[];
+extern const u64 wndwca7e_modifiers[];
 #endif
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
index e2c55f4b9c5a..ef9e410babbf 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
@@ -786,13 +786,14 @@ nv50_wndw_destroy(struct drm_plane *plane)
 }
 
 /* This function assumes the format has already been validated against the
plane
- * and the modifier was validated against the device-wides modifier list at FB
+ * and the modifier was validated against the device-wide modifier list at FB
  * creation time.
  */
 static bool nv50_plane_format_mod_supported(struct drm_plane *plane,
 					    u32 format, u64 modifier)
 {
 	struct nouveau_drm *drm = nouveau_drm(plane->dev);
+	const struct drm_format_info *info = drm_format_info(format);
 	uint8_t i;
 
 	/* All chipsets can display all formats in linear layout */
@@ -800,13 +801,32 @@ static bool nv50_plane_format_mod_supported(struct
drm_plane *plane,
 		return true;
 
 	if (drm->client.device.info.chipset < 0xc0) {
-		const struct drm_format_info *info = drm_format_info(format);
 		const uint8_t kind = (modifier >> 12) & 0xff;
 
 		if (!format) return false;
 
 		for (i = 0; i < info->num_planes; i++)
 			if ((info->cpp[i] != 4) && kind != 0x70) return false;
+	} else if (drm->client.device.info.chipset >= 0x1b2) {
+		const uint8_t slayout = ((modifier >> 22) & 0x1) |
+			((modifier >> 25) & 0x6);
+
+		if (!format)
+			return false;
+
+		/*
+		 * Note in practice this implies only formats where cpp is equal
+		 * for each plane, or >= 4 for all planes, are supported.
+		 */
+		for (i = 0; i < info->num_planes; i++) {
+			if (((info->cpp[i] == 2) && slayout != 3) ||
+			    ((info->cpp[i] == 1) && slayout != 2) ||
+			    ((info->cpp[i] >= 4) && slayout != 1))
+				return false;
+
+			/* 24-bit not supported. It has yet another layout */
+			WARN_ON(info->cpp[i] == 3);
+		}
 	}
 
 	return true;
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
b/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
index 0d8e9a9d1a57..2cec8cfbd546 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
@@ -179,6 +179,39 @@ wndwca7e_ntfy_set(struct nv50_wndw *wndw, struct
nv50_wndw_atom *asyw)
 	return 0;
 }
 
+/****************************************************************
+ *            Log2(block height) ----------------------------+  *
+ *            Page Kind ----------------------------------+  |  *
+ *            Gob Height/Page Kind Generation ------+     |  |  *
+ *                          Sector layout -------+  |     |  |  *
+ *                          Compression ------+  |  |     |  |  */
+const u64 wndwca7e_modifiers[] = { /*         |  |  |     |  |  */
+	/* 4cpp+ modifiers */
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 1, 2, 0x06, 0),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 1, 2, 0x06, 1),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 1, 2, 0x06, 2),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 1, 2, 0x06, 3),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 1, 2, 0x06, 4),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 1, 2, 0x06, 5),
+	/* 1cpp/8bpp modifiers */
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 2, 2, 0x06, 0),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 2, 2, 0x06, 1),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 2, 2, 0x06, 2),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 2, 2, 0x06, 3),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 2, 2, 0x06, 4),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 2, 2, 0x06, 5),
+	/* 2cpp/16bpp modifiers */
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 3, 2, 0x06, 0),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 3, 2, 0x06, 1),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 3, 2, 0x06, 2),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 3, 2, 0x06, 3),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 3, 2, 0x06, 4),
+	DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D(0, 3, 2, 0x06, 5),
+	/* All formats support linear */
+	DRM_FORMAT_MOD_LINEAR,
+	DRM_FORMAT_MOD_INVALID
+};
+
 static const struct nv50_wndw_func
 wndwca7e = {
 	.acquire = wndwc37e_acquire,
-- 
2.50.1

Dave Airlie

2025-Nov-06 01:10 UTC

head link

[PATCH v2 0/2] drm/nouveau: Advertise correct modifiers on GB20x

I've pushed both of these to drm-misc-fixes.

Thanks,
Dave.

On Fri, 31 Oct 2025 at 04:07, James Jones <jajones at nvidia.com>
wrote:>
> This series adds new format modifiers for 8 and 16-bit formats on GB20x
> GPUs, preventing them from mistakenly sharing block-linear surfaces
> using these formats with prior GPUs that use a different layout.
>
> There are a few ways the parameteric format modifier definition
> could have been altered to handle the new layouts:
>
> -The GOB Height and Page Kind field has a reserved value that could
>  have been used. However, the GOB height and page kind enums did
>  not change relative to prior chips, so this is sort of a lie.
>  However, this is the least-invasive change.
>
> -An entirely new field could have been added. This seems
>  inappropriate given the presence of an existing appropriate field.
>  The advantage here is it avoids splitting the sector layout field
>  across two bitfields.
>
> The chosen approach is the logically consistent one, but has the
> downside of being the most complex, and that it causes the
> DRM_FORMAT_MOD_NVIDIA_BLOCK_LINEAR_2D() macro to evaluate its 's'
> parameter twice. However, utilizing simple helper functions in
> client code when accessing the parameteric format modifier fields
> easily addresses the complexity, and I have audited the relevant code
> and do not believe the double evaluation should cause any problems in
> practice.
>
> Tested on GB20x and TU10x cards using the following:
>
> -kmscube w/NVK+Zink built with these patches applied:
>
>    https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36336
>
>  with various manually specified formats
>  and both manually specified and automatically
>  selected modifiers.
>
> -drmfmtmods, a tiny test program that lists modifiers:
>
>    https://github.com/cubanismo/drmfmtmods
>
> Changes in v2:
>
> -Added "Fixes: 6cc6e08d4542" line since this can be considered a
bug
>  fix for the initial blackwell KMS support in nouveau.
>
> -Dropped the second patch from the v1 series as it has been merged.
>
> Changes since the RFC version here:
>
>   https://lore.kernel.org/nouveau/20250703223658.1457-1-jajones at
nvidia.com/
>
> -Dropped the helper macros & static inlines in
>  drm_fourcc.h as requested by Faith Ekstrand,
>  who noted these aren't helpful for UMD code,
>  which is all written in rust now. I may re-
>  introduce some of these in a subsequent series,
>  but we both agreed we do not want to delay
>  progress on the modifiers themselves while we
>  debate the details of those cometic details.
>
> -Reserved an extra bit for future sector
>  layouts.
>
> -Fixed handling of linear modifiers on GB20x
>  and NV5x/G8x/G9x/GT2xx chips.
>
> James Jones (2):
>   drm: define NVIDIA DRM format modifiers for GB20x
>   drm/nouveau: Advertise correct modifiers on GB20x
>
>  drivers/gpu/drm/nouveau/dispnv50/disp.c     |  4 ++-
>  drivers/gpu/drm/nouveau/dispnv50/disp.h     |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/wndw.c     | 24 +++++++++++++--
>  drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c | 33 +++++++++++++++++++++
>  include/uapi/drm/drm_fourcc.h               | 25 ++++++++++------
>  5 files changed, 75 insertions(+), 12 deletions(-)
>
> --
> 2.50.1
>

Nouveau - Oct 2025 - [PATCH v2 0/2] drm/nouveau: Advertise correct modifiers on GB20x

[PATCH v2 0/2] drm/nouveau: Advertise correct modifiers on GB20x

[PATCH v2 1/2] drm: define NVIDIA DRM format modifiers for GB20x

[PATCH v2 2/2] drm/nouveau: Advertise correct modifiers on GB20x

[PATCH v2 0/2] drm/nouveau: Advertise correct modifiers on GB20x