[PATCH] drm/panfrost: Update io-pgtable API

[Dmitry Osipenko]

On 8/23/22 01:01, Robin Murphy wrote:
> Convert to io-pgtable's bulk {map,unmap}_pages() APIs, to help the old
> single-page interfaces eventually go away. Unmapping heap BOs still
> wants to be done a page at a time, but everything else can get the full
> benefit of the more efficient interface.
> 
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 40 +++++++++++++++----------
>  1 file changed, 25 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index b285a8001b1d..e246d914e7f6 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -248,11 +248,15 @@ void panfrost_mmu_reset(struct panfrost_device *pfdev)
>  	mmu_write(pfdev, MMU_INT_MASK, ~0);
>  }
>  
> -static size_t get_pgsize(u64 addr, size_t size)
> +static size_t get_pgsize(u64 addr, size_t size, size_t *count)
>  {
> -	if (addr & (SZ_2M - 1) || size < SZ_2M)
> -		return SZ_4K;
> +	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;
>  	return SZ_2M;
>  }
>  
> @@ -287,12 +291,16 @@ static int mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
>  		dev_dbg(pfdev->dev, "map: as=%d, iova=%llx, paddr=%lx, len=%zx", mmu->as, iova, paddr, len);
>  
>  		while (len) {
> -			size_t pgsize = get_pgsize(iova | paddr, len);
> +			size_t pgcount, mapped = 0;
> +			size_t pgsize = get_pgsize(iova | paddr, len, &pgcount);
>  
> -			ops->map(ops, iova, paddr, pgsize, prot, GFP_KERNEL);
> -			iova += pgsize;
> -			paddr += pgsize;
> -			len -= pgsize;
> +			ops->map_pages(ops, iova, paddr, pgsize, pgcount, prot,
> +				       GFP_KERNEL, &mapped);
> +			/* Don't get stuck if things have gone wrong */
> +			mapped = max(mapped, pgsize);
> +			iova += mapped;
> +			paddr += mapped;
> +			len -= mapped;
>  		}
>  	}
>  
> @@ -344,15 +352,17 @@ void panfrost_mmu_unmap(struct panfrost_gem_mapping *mapping)
>  		mapping->mmu->as, iova, len);
>  
>  	while (unmapped_len < len) {
> -		size_t unmapped_page;
> -		size_t pgsize = get_pgsize(iova, len - unmapped_len);
> +		size_t unmapped_page, pgcount;
> +		size_t pgsize = get_pgsize(iova, len - unmapped_len, &pgcount);
>  
> -		if (ops->iova_to_phys(ops, iova)) {
> -			unmapped_page = ops->unmap(ops, iova, pgsize, NULL);
> -			WARN_ON(unmapped_page != pgsize);
> +		if (bo->is_heap)
> +			pgcount = 1;
> +		if (!bo->is_heap || ops->iova_to_phys(ops, iova)) {
> +			unmapped_page = ops->unmap_pages(ops, iova, pgsize, pgcount, NULL);
> +			WARN_ON(unmapped_page != pgsize * pgcount);

This patch causes this WARN_ON to trigger. It doesn't happen all the
time, I see that the whole unmapped area is mapped. Initially, I thought
that this happens because it tries to unmap a partially mapped range,
but I checked that ops->iova_to_phys() returns address for all 4k chunks.

For example the pgsize * pgcount = 0x8000000, while returned
unmapped_page = 0x6000000.

I don't see this problem with this patch reverted. This is using today's
linux-next. Any ideas?

-- 
Best regards,
Dmitry