Re: [PATCH] drm/panfrost: Split io-pgtable requests properly
On 08/11/2022 17:06, Robin Murphy wrote:
> Although we don't use 1GB block mappings, we still need to split
> map/unmap requests at 1GB boundaries to match what io-pgtable expects.
> Fix that, and add some explanation to make sense of it all.
>
> Fixes: 3740b081795a ("drm/panfrost: Update io-pgtable API")
> Reported-by: Dmitry Osipenko
> Signed-off-by: Robin Murphy
Reviewed-by: Steven Price
I'll push to drm-misc-fixes.
Thanks,
Steve
> ---
> The previous diff turned out to be not quite right, so I've not
> included Dmitry's Tested-by given for that.
> ---
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 11 ++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index e246d914e7f6..4e83a1891f3e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -250,13 +250,22 @@ void panfrost_mmu_reset(struct panfrost_device *pfdev)
>
> static size_t get_pgsize(u64 addr, size_t size, size_t *count)
> {
> + /*
> + * io-pgtable only operates on multiple pages within a single table
> + * entry, so we need to split at boundaries of the table size, i.e.
> + * the next block size up. The distance from address A to the next
> + * boundary of block size B is logically B - A % B, but in unsigned
> + * two's complement where B is a power of two we get the equivalence
> + * B - A % B == (B - A) % B == (n * B - A) % B, and choose n = 0 :)
> + */
> size_t blk_offset = -addr % SZ_2M;
>
> if (blk_offset || size < SZ_2M) {
> *count = min_not_zero(blk_offset, size) / SZ_4K;
> return SZ_4K;
> }
> - *count = size / SZ_2M;
> + blk_offset = -addr % SZ_1G ?: SZ_1G;
> + *count = min(blk_offset, size) / SZ_2M;
> return SZ_2M;
> }
>
Re: [PATCH] drm/panfrost: Split io-pgtable requests properly
On 11/8/22 20:06, Robin Murphy wrote:
> Although we don't use 1GB block mappings, we still need to split
> map/unmap requests at 1GB boundaries to match what io-pgtable expects.
> Fix that, and add some explanation to make sense of it all.
>
> Fixes: 3740b081795a ("drm/panfrost: Update io-pgtable API")
> Reported-by: Dmitry Osipenko
> Signed-off-by: Robin Murphy
> ---
> The previous diff turned out to be not quite right, so I've not
> included Dmitry's Tested-by given for that.
> ---
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 11 ++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index e246d914e7f6..4e83a1891f3e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -250,13 +250,22 @@ void panfrost_mmu_reset(struct panfrost_device *pfdev)
>
> static size_t get_pgsize(u64 addr, size_t size, size_t *count)
> {
> + /*
> + * io-pgtable only operates on multiple pages within a single table
> + * entry, so we need to split at boundaries of the table size, i.e.
> + * the next block size up. The distance from address A to the next
> + * boundary of block size B is logically B - A % B, but in unsigned
> + * two's complement where B is a power of two we get the equivalence
> + * B - A % B == (B - A) % B == (n * B - A) % B, and choose n = 0 :)
> + */
> size_t blk_offset = -addr % SZ_2M;
>
> if (blk_offset || size < SZ_2M) {
> *count = min_not_zero(blk_offset, size) / SZ_4K;
> return SZ_4K;
> }
> - *count = size / SZ_2M;
> + blk_offset = -addr % SZ_1G ?: SZ_1G;
> + *count = min(blk_offset, size) / SZ_2M;
> return SZ_2M;
> }
>
This variant also works fine, thanks!
Tested-by: Dmitry Osipenko
--
Best regards,
Dmitry
[PATCH] drm/panfrost: Split io-pgtable requests properly
Although we don't use 1GB block mappings, we still need to split
map/unmap requests at 1GB boundaries to match what io-pgtable expects.
Fix that, and add some explanation to make sense of it all.
Fixes: 3740b081795a ("drm/panfrost: Update io-pgtable API")
Reported-by: Dmitry Osipenko
Signed-off-by: Robin Murphy
---
The previous diff turned out to be not quite right, so I've not
included Dmitry's Tested-by given for that.
---
drivers/gpu/drm/panfrost/panfrost_mmu.c | 11 ++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c
b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index e246d914e7f6..4e83a1891f3e 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -250,13 +250,22 @@ void panfrost_mmu_reset(struct panfrost_device *pfdev)
static size_t get_pgsize(u64 addr, size_t size, size_t *count)
{
+ /*
+* io-pgtable only operates on multiple pages within a single table
+* entry, so we need to split at boundaries of the table size, i.e.
+* the next block size up. The distance from address A to the next
+* boundary of block size B is logically B - A % B, but in unsigned
+* two's complement where B is a power of two we get the equivalence
+* B - A % B == (B - A) % B == (n * B - A) % B, and choose n = 0 :)
+*/
size_t blk_offset = -addr % SZ_2M;
if (blk_offset || size < SZ_2M) {
*count = min_not_zero(blk_offset, size) / SZ_4K;
return SZ_4K;
}
- *count = size / SZ_2M;
+ blk_offset = -addr % SZ_1G ?: SZ_1G;
+ *count = min(blk_offset, size) / SZ_2M;
return SZ_2M;
}
--
2.36.1.dirty
