Hi Am 23.09.20 um 16:27 schrieb Christian König: > 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: >> +.. 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. >> + */ >> +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. I've been trying to separate I/O and system memory as much as possible. I'd rather leave it as it is. Best regards Thomas > >> +} >> + >> +/** >> + * 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. > > 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; > -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
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