Am Montag, den 19.05.2014, 18:46 +0900 schrieb Alexandre Courbot:
This patch is not meant to be merged, but rather to try and understand why this is needed and what a more suitable solution could be.
Allowing BOs to be write-cached results in the following happening when trying to run any program on Tegra/GK20A:
Unhandled fault: external abort on non-linefetch (0x1008) at 0xf0036010 ... (nouveau_bo_rd32) from [<c0357d00>] (nouveau_fence_update+0x5c/0x80) (nouveau_fence_update) from [<c0357d40>] (nouveau_fence_done+0x1c/0x38) (nouveau_fence_done) from [<c02c3d00>] (ttm_bo_wait+0xec/0x168) (ttm_bo_wait) from [<c035e334>] (nouveau_gem_ioctl_cpu_prep+0x44/0x100) (nouveau_gem_ioctl_cpu_prep) from [<c02aaa84>] (drm_ioctl+0x1d8/0x4f4) (drm_ioctl) from [<c0355394>] (nouveau_drm_ioctl+0x54/0x80) (nouveau_drm_ioctl) from [<c00ee7b0>] (do_vfs_ioctl+0x3dc/0x5a0) (do_vfs_ioctl) from [<c00ee9a8>] (SyS_ioctl+0x34/0x5c) (SyS_ioctl) from [<c000e6e0>] (ret_fast_syscall+0x0/0x30
The offending nouveau_bo_rd32 is done over an IO-mapped BO, e.g. a BO mapped through the BAR.
Um wait, this memory is behind an already mapped bar? I think ioremap on ARM defaults to uncached mappings, so if you want to access the memory behind this bar as WC you need to map the BAR as a whole as WC by using ioremap_wc.
Regards, Lucas
Any idea about the origin of this behavior? Does ARM forbid cached mappings over IO regions?
Signed-off-by: Alexandre Courbot acourbot@nvidia.com
drivers/gpu/drm/nouveau/nouveau_bo.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c index 8db54a217232..9cfb8e61f5c4 100644 --- a/drivers/gpu/drm/nouveau/nouveau_bo.c +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c @@ -552,7 +552,11 @@ nouveau_bo_init_mem_type(struct ttm_bo_device *bdev, uint32_t type, TTM_MEMTYPE_FLAG_MAPPABLE; man->available_caching = TTM_PL_FLAG_UNCACHED | TTM_PL_FLAG_WC; +#if defined(__arm__)
man->default_caching = TTM_PL_FLAG_UNCACHED;+#else man->default_caching = TTM_PL_FLAG_WC; +#endif break; case TTM_PL_TT: if (nv_device(drm->device)->card_type >= NV_50)