[PATCH 6.18 129/752] drm/v3d: Set DMA segment size to avoid debug warnings

Sasha Levin
2026-02-28T17:49:57Z

From: Xiaolei Wang <xiaolei.wang@windriver.com>

[ Upstream commit 9eb018828b1b30dfba689c060735c50fc5b9f704 ]

When using V3D rendering with CONFIG_DMA_API_DEBUG enabled, the
kernel occasionally reports a segment size mismatch. This is because
'max_seg_size' is not set. The kernel defaults to 64K. setting
'max_seg_size' to the maximum will prevent 'debug_dma_map_sg()'
from complaining about the over-mapping of the V3D segment length.

DMA-API: v3d 1002000000.v3d: mapping sg segment longer than device
claims to support [len=8290304] [max=65536]
WARNING: CPU: 0 PID: 493 at kernel/dma/debug.c:1179 debug_dma_map_sg+0x330/0x388
CPU: 0 UID: 0 PID: 493 Comm: Xorg Not tainted 6.12.53-yocto-standard #1
Hardware name: Raspberry Pi 5 Model B Rev 1.0 (DT)
pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : debug_dma_map_sg+0x330/0x388
lr : debug_dma_map_sg+0x330/0x388
sp : ffff8000829a3ac0
x29: ffff8000829a3ac0 x28: 0000000000000001 x27: ffff8000813fe000
x26: ffffc1ffc0000000 x25: ffff00010fdeb760 x24: 0000000000000000
x23: ffff8000816a9bf0 x22: 0000000000000001 x21: 0000000000000002
x20: 0000000000000002 x19: ffff00010185e810 x18: ffffffffffffffff
x17: 69766564206e6168 x16: 74207265676e6f6c x15: 20746e656d676573
x14: 20677320676e6970 x13: 5d34303334393134 x12: 0000000000000000
x11: 00000000000000c0 x10: 00000000000009c0 x9 : ffff8000800e0b7c
x8 : ffff00010a315ca0 x7 : ffff8000816a5110 x6 : 0000000000000001
x5 : 000000000000002b x4 : 0000000000000002 x3 : 0000000000000008
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff00010a315280
Call trace:
debug_dma_map_sg+0x330/0x388
__dma_map_sg_attrs+0xc0/0x278
dma_map_sgtable+0x30/0x58
drm_gem_shmem_get_pages_sgt+0xb4/0x140
v3d_bo_create_finish+0x28/0x130 [v3d]
v3d_create_bo_ioctl+0x54/0x180 [v3d]
drm_ioctl_kernel+0xc8/0x140
drm_ioctl+0x2d4/0x4d8

Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
Link: https://patch.msgid.link/20251203130323.2247072-1-xiaolei.wang@windriver.com
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/v3d/v3d_drv.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/v3d/v3d_drv.c b/drivers/gpu/drm/v3d/v3d_drv.c
index c5a3bbbc74c5c..f4da7a94e4016 100644
--- a/drivers/gpu/drm/v3d/v3d_drv.c
+++ b/drivers/gpu/drm/v3d/v3d_drv.c
@@ -377,6 +377,8 @@ static int v3d_platform_drm_probe(struct platform_device *pdev)
if (ret)
goto clk_disable;

+ dma_set_max_seg_size(&pdev->dev, UINT_MAX);
+
v3d->va_width = 30 + V3D_GET_FIELD(mmu_debug, V3D_MMU_VA_WIDTH);

ident1 = V3D_READ(V3D_HUB_IDENT1);
--
2.51.0