| Message ID | 20221120234441.550908-1-m.grzeschik@pengutronix.de |
|---|---|
| State | New |
| Headers | show |
| Series | media: videobuf2-dma-sg: use v{un,}map instead of vm_{un,}map_ram | expand |
On Wed, Nov 01, 2023 at 12:43:25PM +0900, Tomasz Figa wrote: >On Tue, May 16, 2023 at 7:50 PM Tomasz Figa <tfiga@chromium.org> wrote: >> >> Hi Michael, >> >> On Wed, May 10, 2023 at 11:25 PM Michael Grzeschik <mgr@pengutronix.de> wrote: >> > >> > Sorry for the late comeback, however here are some thoughts. >> > >> > On Fri, Dec 02, 2022 at 06:01:02PM +0900, Tomasz Figa wrote: >> > >On Thu, Nov 24, 2022 at 10:35 PM Hans Verkuil <hverkuil@xs4all.nl> wrote: >> > >> >> > >> On 21/11/2022 00:44, Michael Grzeschik wrote: >> > >> > The comments before the vm_map_ram function state that it should be used >> > >> > for up to 256 KB only, and video buffers are definitely much larger. It >> > >> > recommends using vmap in that case. >> > >> > >> > >> > Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de> >> > >> > --- >> > >> > drivers/media/common/videobuf2/videobuf2-dma-sg.c | 7 ++++--- >> > >> >> > >> drivers/media/common/videobuf2/videobuf2-vmalloc.c uses it as well, >> > >> probably also incorrectly. It makes sense to change that one as well. >> > > >> > >Comparing vm_map_ram() and vmap(..., VM_MAP, PAGE_KERNEL), for blocks >> > >bigger than VMAP_MAX_ALLOC they're equivalent and for smaller blocks >> > >the former should be faster, so I don't see what's wrong with the >> > >current code. >> > >> > I got another comment on this from Andrzej Pietrasiewicz >> > where he expands the comment on the use of vmap over vm_map_ram. >> > >> > https://lore.kernel.org/linux-media/64375ff4-dbbb-3d5b-eaf6-32d6780fd496@collabora.com >> > >> > As I understand this, we should probably update the vm_map_ram to vmap, >> > due to the expectation that video buffers are long-living objects. >> > >> > Since there are some more places that would probably need to be updated >> > if we should decide to use vmap over vm_map_ram in the whole >> > videbuf2-* users, I would like to clarify on this before making >> > a series. >> >> Ah, I see. Thanks for the pointer. >> >> VB2 buffers would usually require long-lived mappings, so based on >> that, we should switch to vmap() indeed. >> >> As a side note, not directly related to this patch, I wonder if we >> should also call invalidate/flush_kernel_vmap_range() in >> vb2_dma_sg_prepare/finish(). (In principle we shouldn't, but so far >> our drivers don't explicitly call begin/end_cpu_access() and rely on >> prepare/finish to handle the cache maintenance of the kernel >> mapping...) Let me also add Sergey on CC for visibility. > >Sorry, I forgot last time, so maybe it wasn't clear I'm good with this patch: > >Acked-by: Tomasz Figa <tfiga@chromium.org> > >Hans, will you pick it? Thanks! Gentle Ping!
Hi Michael, On 15/11/2023 22:46, Michael Grzeschik wrote: > On Wed, Nov 01, 2023 at 12:43:25PM +0900, Tomasz Figa wrote: >> On Tue, May 16, 2023 at 7:50 PM Tomasz Figa <tfiga@chromium.org> wrote: >>> >>> Hi Michael, >>> >>> On Wed, May 10, 2023 at 11:25 PM Michael Grzeschik <mgr@pengutronix.de> wrote: >>> > >>> > Sorry for the late comeback, however here are some thoughts. >>> > >>> > On Fri, Dec 02, 2022 at 06:01:02PM +0900, Tomasz Figa wrote: >>> > >On Thu, Nov 24, 2022 at 10:35 PM Hans Verkuil <hverkuil@xs4all.nl> wrote: >>> > >> >>> > >> On 21/11/2022 00:44, Michael Grzeschik wrote: >>> > >> > The comments before the vm_map_ram function state that it should be used >>> > >> > for up to 256 KB only, and video buffers are definitely much larger. It >>> > >> > recommends using vmap in that case. >>> > >> > >>> > >> > Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de> >>> > >> > --- >>> > >> > drivers/media/common/videobuf2/videobuf2-dma-sg.c | 7 ++++--- >>> > >> >>> > >> drivers/media/common/videobuf2/videobuf2-vmalloc.c uses it as well, >>> > >> probably also incorrectly. It makes sense to change that one as well. >>> > > >>> > >Comparing vm_map_ram() and vmap(..., VM_MAP, PAGE_KERNEL), for blocks >>> > >bigger than VMAP_MAX_ALLOC they're equivalent and for smaller blocks >>> > >the former should be faster, so I don't see what's wrong with the >>> > >current code. >>> > >>> > I got another comment on this from Andrzej Pietrasiewicz >>> > where he expands the comment on the use of vmap over vm_map_ram. >>> > >>> > https://lore.kernel.org/linux-media/64375ff4-dbbb-3d5b-eaf6-32d6780fd496@collabora.com >>> > >>> > As I understand this, we should probably update the vm_map_ram to vmap, >>> > due to the expectation that video buffers are long-living objects. >>> > >>> > Since there are some more places that would probably need to be updated >>> > if we should decide to use vmap over vm_map_ram in the whole >>> > videbuf2-* users, I would like to clarify on this before making >>> > a series. >>> >>> Ah, I see. Thanks for the pointer. >>> >>> VB2 buffers would usually require long-lived mappings, so based on >>> that, we should switch to vmap() indeed. >>> >>> As a side note, not directly related to this patch, I wonder if we >>> should also call invalidate/flush_kernel_vmap_range() in >>> vb2_dma_sg_prepare/finish(). (In principle we shouldn't, but so far >>> our drivers don't explicitly call begin/end_cpu_access() and rely on >>> prepare/finish to handle the cache maintenance of the kernel >>> mapping...) Let me also add Sergey on CC for visibility. >> >> Sorry, I forgot last time, so maybe it wasn't clear I'm good with this patch: >> >> Acked-by: Tomasz Figa <tfiga@chromium.org> >> >> Hans, will you pick it? Thanks! > > Gentle Ping! > This patch is marked with "Changes Requested" in patchwork: https://patchwork.linuxtv.org/project/linux-media/patch/20221120234441.550908-1-m.grzeschik@pengutronix.de/ Looking at the comments, there is a request to improve a comment and a request from me to make the same change to videobuf2-vmalloc.c. I have no problem with the change itself, it makes sense to use vmap. In any case, a v2 is needed. Regards, Hans
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c index dcb8de5ab3e84a..e86621fba350f3 100644 --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c @@ -188,7 +188,7 @@ static void vb2_dma_sg_put(void *buf_priv) dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC); if (buf->vaddr) - vm_unmap_ram(buf->vaddr, buf->num_pages); + vunmap(buf->vaddr); sg_free_table(buf->dma_sgt); while (--i >= 0) __free_page(buf->pages[i]); @@ -289,7 +289,7 @@ static void vb2_dma_sg_put_userptr(void *buf_priv) __func__, buf->num_pages); dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC); if (buf->vaddr) - vm_unmap_ram(buf->vaddr, buf->num_pages); + vunmap(buf->vaddr); sg_free_table(buf->dma_sgt); if (buf->dma_dir == DMA_FROM_DEVICE || buf->dma_dir == DMA_BIDIRECTIONAL) @@ -312,7 +312,8 @@ static void *vb2_dma_sg_vaddr(struct vb2_buffer *vb, void *buf_priv) ret = dma_buf_vmap(buf->db_attach->dmabuf, &map); buf->vaddr = ret ? NULL : map.vaddr; } else { - buf->vaddr = vm_map_ram(buf->pages, buf->num_pages, -1); + buf->vaddr = vmap(buf->pages, buf->num_pages, VM_MAP, + PAGE_KERNEL); } }
The comments before the vm_map_ram function state that it should be used for up to 256 KB only, and video buffers are definitely much larger. It recommends using vmap in that case. Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de> --- drivers/media/common/videobuf2/videobuf2-dma-sg.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)