20. 4. 7. 오후 10:42에 Marek Szyprowski 이(가) 쓴 글:
> Explicitly check if the imported buffer has been mapped as contiguous in
> the DMA address space, what is required by all Exynos DRM CRTC drivers.
> While touching this, set buffer flags depending on the availability of
> the IOMMU.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/exynos/exynos_drm_gem.c | 36 +++++++++++++++++--------
> 1 file changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
> index 40514d3dcf60..9d4e4d321bda 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
> @@ -458,6 +458,23 @@ exynos_drm_gem_prime_import_sg_table(struct drm_device *dev,
> int npages;
> int ret;
>
(Optional) could you leave one comment here?
i.e., /* Check if DMA memory region from a exporter are mapped contiguously or not. */
> + if (sgt->nents != 1) {
How about using below condition instead?
if (sgt->nents > 0) {
> + dma_addr_t next_addr = sg_dma_address(sgt->sgl);
> + struct scatterlist *s;
> + unsigned int i;
> +
> + for_each_sg(sgt->sgl, s, sgt->nents, i) {
> + if (!sg_dma_len(s))
> + continue;
Isn't it an error case if sg_dma_len(s) is 0? I think length of s is 0 then it would be invalid because all entries of sgt should be mapped before sg_dma_len() is called.
Thanks,
Inki Dae
> + if (sg_dma_address(s) != next_addr) {
> + DRM_ERROR("buffer chunks must be mapped contiguously");
> + return ERR_PTR(-EINVAL);
> + }
> + next_addr = sg_dma_address(s) + sg_dma_len(s);
> + }
> + return ERR_PTR(-EINVAL);
> + }
> +
> exynos_gem = exynos_drm_gem_init(dev, attach->dmabuf->size);
> if (IS_ERR(exynos_gem)) {
> ret = PTR_ERR(exynos_gem);
> @@ -480,18 +497,15 @@ exynos_drm_gem_prime_import_sg_table(struct drm_device *dev,
>
> exynos_gem->sgt = sgt;
>
> - if (sgt->nents == 1) {
> - /* always physically continuous memory if sgt->nents is 1. */
> - exynos_gem->flags |= EXYNOS_BO_CONTIG;
> - } else {
> - /*
> - * this case could be CONTIG or NONCONTIG type but for now
> - * sets NONCONTIG.
> - * TODO. we have to find a way that exporter can notify
> - * the type of its own buffer to importer.
> - */
> + /*
> + * Buffer has been mapped as contiguous into DMA address space,
> + * but if there is IOMMU, it can be either CONTIG or NONCONTIG.
> + * We assume a simplified logic below:
> + */
> + if (is_drm_iommu_supported(dev))
> exynos_gem->flags |= EXYNOS_BO_NONCONTIG;
> - }
> + else
> + exynos_gem->flags |= EXYNOS_BO_CONTIG;
>
> return &exynos_gem->base;
>
>
