The RISC-V Svpbmt privileged extension provides support for overriding
page memory coherency attributes, and, along with vendor extensions like
Xtheadmae, supports pgprot_{writecombine,noncached} on RISC-V.

Adapt the codepath that maps ttm_write_combined to pgprot_writecombine
and ttm_noncached to pgprot_noncached to RISC-V, to allow proper page
access attributes.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
---
 drivers/gpu/drm/ttm/ttm_module.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_module.c b/drivers/gpu/drm/ttm/ttm_module.c
index b3fffe7b5062..aa137ead5cc5 100644
--- a/drivers/gpu/drm/ttm/ttm_module.c
+++ b/drivers/gpu/drm/ttm/ttm_module.c
@@ -74,7 +74,8 @@ pgprot_t ttm_prot_from_caching(enum ttm_caching caching, pgprot_t tmp)
 #endif /* CONFIG_UML */
 #endif /* __i386__ || __x86_64__ */
 #if defined(__ia64__) || defined(__arm__) || defined(__aarch64__) || \
-	defined(__powerpc__) || defined(__mips__) || defined(__loongarch__)
+	defined(__powerpc__) || defined(__mips__) || defined(__loongarch__) || \
+	defined(__riscv)
 	if (caching == ttm_write_combined)
 		tmp = pgprot_writecombine(tmp);
 	else
-- 
2.50.1

On Tue, Jul 22, 2025 at 7:21 PM Icenowy Zheng <uwu@icenowy.me> wrote:
>
> The RISC-V Svpbmt privileged extension provides support for overriding
> page memory coherency attributes, and, along with vendor extensions like
> Xtheadmae, supports pgprot_{writecombine,noncached} on RISC-V.
>
> Adapt the codepath that maps ttm_write_combined to pgprot_writecombine
> and ttm_noncached to pgprot_noncached to RISC-V, to allow proper page
> access attributes.
>
> Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> ---
>  drivers/gpu/drm/ttm/ttm_module.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_module.c b/drivers/gpu/drm/ttm/ttm_module.c
> index b3fffe7b5062..aa137ead5cc5 100644
> --- a/drivers/gpu/drm/ttm/ttm_module.c
> +++ b/drivers/gpu/drm/ttm/ttm_module.c
> @@ -74,7 +74,8 @@ pgprot_t ttm_prot_from_caching(enum ttm_caching caching, pgprot_t tmp)
>  #endif /* CONFIG_UML */
>  #endif /* __i386__ || __x86_64__ */
>  #if defined(__ia64__) || defined(__arm__) || defined(__aarch64__) || \
> -       defined(__powerpc__) || defined(__mips__) || defined(__loongarch__)
> +       defined(__powerpc__) || defined(__mips__) || defined(__loongarch__) || \
> +       defined(__riscv)
>         if (caching == ttm_write_combined)
>                 tmp = pgprot_writecombine(tmp);
>         else
> --
> 2.50.1
>

Tested-by: Han Gao <rabenda.cn@gmail.com>

Thanks.