On Wed, Sep 23, 2020 at 04:27:04PM +0200, Christian König wrote: > Am 23.09.20 um 14:32 schrieb Thomas Zimmermann: > > The new type struct dma_buf_map represents a mapping of dma-buf memory > > into kernel space. It contains a flag, is_iomem, that signals users to > > access the mapped memory with I/O operations instead of regular loads > > and stores. > > > > It was assumed that DMA buffer memory can be accessed with regular load > > and store operations. Some architectures, such as sparc64, require the > > use of I/O operations to access dma-map buffers that are located in I/O > > memory. Providing struct dma_buf_map allows drivers to implement this. > > This was specifically a problem when refreshing the graphics framebuffer > > on such systems. [1] > > > > As the first step, struct dma_buf stores an instance of struct dma_buf_map > > internally. Afterwards, dma-buf's vmap and vunmap interfaces are be > > converted. Finally, affected drivers can be fixed. > > > > [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdri-devel%2F20200725191012.GA434957%40ravnborg.org%2F&data=02%7C01%7Cchristian.koenig%40amd.com%7C54486b9682654f3950b808d85fbcb1d3%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637364611338153209&sdata=%2BZm7t8OcgkIxnY%2FdZSLhSbKC7t1y4VW5lINFKwCQv3A%3D&reserved=0 > > Only two nit picks below, apart from that Reviewed-by: Christian König > <christian.koenig@xxxxxxx> > > > > > Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> > > Acked-by: Sumit Semwal <sumit.semwal@xxxxxxxxxx> > > --- > > Documentation/driver-api/dma-buf.rst | 3 + > > drivers/dma-buf/dma-buf.c | 14 ++--- > > include/linux/dma-buf-map.h | 87 ++++++++++++++++++++++++++++ > > include/linux/dma-buf.h | 3 +- > > 4 files changed, 99 insertions(+), 8 deletions(-) > > create mode 100644 include/linux/dma-buf-map.h > > > > diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst > > index 13ea0cc0a3fa..3244c600a9a1 100644 > > --- a/Documentation/driver-api/dma-buf.rst > > +++ b/Documentation/driver-api/dma-buf.rst > > @@ -115,6 +115,9 @@ Kernel Functions and Structures Reference > > .. kernel-doc:: include/linux/dma-buf.h > > :internal: Please add a heading here, maybe "Buffer mapping helpers" or somethig like that. > > +.. kernel-doc:: include/linux/dma-buf-map.h > > + :internal: > > + > > Reservation Objects > > ------------------- > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > > index 58564d82a3a2..5e849ca241a0 100644 > > --- a/drivers/dma-buf/dma-buf.c > > +++ b/drivers/dma-buf/dma-buf.c > > @@ -1207,12 +1207,12 @@ void *dma_buf_vmap(struct dma_buf *dmabuf) > > mutex_lock(&dmabuf->lock); > > if (dmabuf->vmapping_counter) { > > dmabuf->vmapping_counter++; > > - BUG_ON(!dmabuf->vmap_ptr); > > - ptr = dmabuf->vmap_ptr; > > + BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr)); > > + ptr = dmabuf->vmap_ptr.vaddr; > > goto out_unlock; > > } > > - BUG_ON(dmabuf->vmap_ptr); > > + BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr)); > > ptr = dmabuf->ops->vmap(dmabuf); > > if (WARN_ON_ONCE(IS_ERR(ptr))) > > @@ -1220,7 +1220,7 @@ void *dma_buf_vmap(struct dma_buf *dmabuf) > > if (!ptr) > > goto out_unlock; > > - dmabuf->vmap_ptr = ptr; > > + dmabuf->vmap_ptr.vaddr = ptr; > > dmabuf->vmapping_counter = 1; > > out_unlock: > > @@ -1239,15 +1239,15 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) > > if (WARN_ON(!dmabuf)) > > return; > > - BUG_ON(!dmabuf->vmap_ptr); > > + BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr)); > > BUG_ON(dmabuf->vmapping_counter == 0); > > - BUG_ON(dmabuf->vmap_ptr != vaddr); > > + BUG_ON(!dma_buf_map_is_vaddr(&dmabuf->vmap_ptr, vaddr)); > > mutex_lock(&dmabuf->lock); > > if (--dmabuf->vmapping_counter == 0) { > > if (dmabuf->ops->vunmap) > > dmabuf->ops->vunmap(dmabuf, vaddr); > > - dmabuf->vmap_ptr = NULL; > > + dma_buf_map_clear(&dmabuf->vmap_ptr); > > } > > mutex_unlock(&dmabuf->lock); > > } > > diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h > > new file mode 100644 > > index 000000000000..d4b1bb3cc4b0 > > --- /dev/null > > +++ b/include/linux/dma-buf-map.h > > @@ -0,0 +1,87 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > +/* > > + * Pointer to dma-buf-mapped memory, plus helpers. > > + */ > > + > > +#ifndef __DMA_BUF_MAP_H__ > > +#define __DMA_BUF_MAP_H__ > > + > > +#include <linux/io.h> > > + > > +/** > > + * struct dma_buf_map - Pointer to vmap'ed dma-buf memory. > > + * @vaddr_iomem: The buffer's address if in I/O memory > > + * @vaddr: The buffer's address if in system memory > > + * @is_iomem: True if the dma-buf memory is located in I/O > > + * memory, or false otherwise. > > + * > > + * Calling dma-buf's vmap operation returns a pointer to the buffer. > > + * Depending on the location of the buffer, users may have to access it > > + * with I/O operations or memory load/store operations. struct dma_buf_map > > + * stores the buffer address and a flag that signals the required access. Maybe explain that this can be used in general for abstracting away the difference between system memory and __iomem for buffer mappings. Or something like that - it's not exlusively tied to dma-buf, just a convenient place. > > + */ > > +struct dma_buf_map { > > + union { > > + void __iomem *vaddr_iomem; > > + void *vaddr; > > + }; > > + bool is_iomem; > > +}; > > + > > +/* API transition helper */ > > +static inline bool dma_buf_map_is_vaddr(const struct dma_buf_map *map, const void *vaddr) > > +{ > > + return !map->is_iomem && (map->vaddr == vaddr); > > +} > > + > > +/** > > + * dma_buf_map_is_null - Tests for a dma-buf mapping to be NULL > > + * @map: The dma-buf mapping structure > > + * > > + * Depending on the state of struct dma_buf_map.is_iomem, tests if the > > + * mapping is NULL. > > + * > > + * Returns: > > + * True if the mapping is NULL, or false otherwise. > > + */ > > +static inline bool dma_buf_map_is_null(const struct dma_buf_map *map) > > +{ > > + if (map->is_iomem) > > + return map->vaddr_iomem == NULL; > > + return map->vaddr == NULL; > > This looks like overkill since both pointers are part of the same union. > > I suggest to test only one and add a comment. > > > +} > > + > > +/** > > + * dma_buf_map_is_set - Tests is the dma-buf mapping has been set > > + * @map: The dma-buf mapping structure > > + * > > + * Depending on the state of struct dma_buf_map.is_iomem, tests if the > > + * mapping has been set. > > + * > > + * Returns: > > + * True if the mapping is been set, or false otherwise. > > + */ > > +static inline bool dma_buf_map_is_set(const struct dma_buf_map *map) > > +{ > > + return !dma_buf_map_is_null(map); > > +} > > + > > +/** > > + * dma_buf_map_clear - Clears a dma-buf mapping structure > > + * @map: The dma-buf mapping structure > > + * > > + * Clears all fields to zero; including struct dma_buf_map.is_iomem. So > > + * mapping structures that were set to point to I/O memory are reset for > > + * system memory. Pointers are cleared to NULL. This is the default. > > + */ > > +static inline void dma_buf_map_clear(struct dma_buf_map *map) > > +{ > > + if (map->is_iomem) { > > + map->vaddr_iomem = NULL; > > + map->is_iomem = false; > > + } else { > > + map->vaddr = NULL; > > + } > > Maybe just use memset() on the structure. gcc should be able to see through this, and I think the clever code is maybe a bit too clever. I'd leave it as-is. Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > Christian. > > > +} > > + > > +#endif /* __DMA_BUF_MAP_H__ */ > > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > > index 957b398d30e5..fcc2ddfb6d18 100644 > > --- a/include/linux/dma-buf.h > > +++ b/include/linux/dma-buf.h > > @@ -13,6 +13,7 @@ > > #ifndef __DMA_BUF_H__ > > #define __DMA_BUF_H__ > > +#include <linux/dma-buf-map.h> > > #include <linux/file.h> > > #include <linux/err.h> > > #include <linux/scatterlist.h> > > @@ -309,7 +310,7 @@ struct dma_buf { > > const struct dma_buf_ops *ops; > > struct mutex lock; > > unsigned vmapping_counter; > > - void *vmap_ptr; > > + struct dma_buf_map vmap_ptr; > > const char *exp_name; > > const char *name; > > spinlock_t name_lock; > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
