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From: Michael Freidkin <freidkin@gmail.com>
To: Neil Armstrong <neil.armstrong@linaro.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kevin Hilman <khilman@baylibre.com>,
	Jerome Brunet <jbrunet@baylibre.com>,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	linux-media@vger.kernel.org, linux-amlogic@lists.infradead.org,
	linux-staging@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] media: meson: vdec: size capture planes from the aligned canvas
Date: Mon, 28 Sep 2026 19:50:45 +0300	[thread overview]
Message-ID: <20260928165045.642354-1-freidkin@gmail.com> (raw)

The decoder writes a whole canvas of ALIGN(width, 32) x ALIGN(height, 32)
(amvdec_set_canvases()) and reports bytesperline = ALIGN(width, 32), but
get_output_size() derives sizeimage from the raw width x height.

When the width is not a multiple of 32 the planes are too small for the
advertised stride: for 720x360 NV12M the luma plane is 262144 bytes while
736 * 360 = 264960 are needed (282624 for the canvas the firmware fills).
The decoder writes past the buffer, and importing the capture dma-buf
into DRM fails: drmModeAddFB2() returns -EINVAL, so e.g. Kodi plays the
sound over a black screen. 1280x720 and 1920x1080 are not affected.

Size the planes from the aligned canvas the hardware actually uses.

Tested on an S905X (GXL p212) board with LibreELEC 12 (6.16.0-rc3):
720x360 and 1920x1080 H.264 play through V4L2 m2m + DRM PRIME with no
AddFB2 errors.

Fixes: 3e7f51bd9607 ("media: meson: add v4l2 m2m video decoder driver")
Signed-off-by: Michael Freidkin <freidkin@gmail.com>
---
 drivers/staging/media/meson/vdec/vdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/media/meson/vdec/vdec.c
+++ b/drivers/staging/media/meson/vdec/vdec.c
@@ -34,7 +34,7 @@
 
 static u32 get_output_size(u32 width, u32 height)
 {
-	return ALIGN(width * height, SZ_64K);
+	return ALIGN(ALIGN(width, 32) * ALIGN(height, 32), SZ_64K);
 }
 
 u32 amvdec_get_output_size(struct amvdec_session *sess)
--

WARNING: multiple messages have this Message-ID (diff)
From: Michael Freidkin <freidkin@gmail.com>
To: Neil Armstrong <neil.armstrong@linaro.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kevin Hilman <khilman@baylibre.com>,
	Jerome Brunet <jbrunet@baylibre.com>,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	linux-media@vger.kernel.org, linux-amlogic@lists.infradead.org,
	linux-staging@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] media: meson: vdec: size capture planes from the aligned canvas
Date: Mon, 28 Sep 2026 19:50:45 +0300	[thread overview]
Message-ID: <20260928165045.642354-1-freidkin@gmail.com> (raw)

The decoder writes a whole canvas of ALIGN(width, 32) x ALIGN(height, 32)
(amvdec_set_canvases()) and reports bytesperline = ALIGN(width, 32), but
get_output_size() derives sizeimage from the raw width x height.

When the width is not a multiple of 32 the planes are too small for the
advertised stride: for 720x360 NV12M the luma plane is 262144 bytes while
736 * 360 = 264960 are needed (282624 for the canvas the firmware fills).
The decoder writes past the buffer, and importing the capture dma-buf
into DRM fails: drmModeAddFB2() returns -EINVAL, so e.g. Kodi plays the
sound over a black screen. 1280x720 and 1920x1080 are not affected.

Size the planes from the aligned canvas the hardware actually uses.

Tested on an S905X (GXL p212) board with LibreELEC 12 (6.16.0-rc3):
720x360 and 1920x1080 H.264 play through V4L2 m2m + DRM PRIME with no
AddFB2 errors.

Fixes: 3e7f51bd9607 ("media: meson: add v4l2 m2m video decoder driver")
Signed-off-by: Michael Freidkin <freidkin@gmail.com>
---
 drivers/staging/media/meson/vdec/vdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/media/meson/vdec/vdec.c
+++ b/drivers/staging/media/meson/vdec/vdec.c
@@ -34,7 +34,7 @@
 
 static u32 get_output_size(u32 width, u32 height)
 {
-	return ALIGN(width * height, SZ_64K);
+	return ALIGN(ALIGN(width, 32) * ALIGN(height, 32), SZ_64K);
 }
 
 u32 amvdec_get_output_size(struct amvdec_session *sess)
--

_______________________________________________
linux-amlogic mailing list
linux-amlogic@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-amlogic

             reply	other threads:[~2026-09-28 16:50 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-28 16:50 Michael Freidkin [this message]
2026-09-28 16:50 ` [PATCH] media: meson: vdec: size capture planes from the aligned canvas Michael Freidkin
2026-09-29  5:46 ` Dan Carpenter
2026-09-29  5:46   ` Dan Carpenter
2026-09-29  6:08   ` Michael Freidkin
2026-09-29  6:08     ` Michael Freidkin
2026-09-29 21:48 ` sashiko-bot

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