Messages in this thread Patch in this message | | | Subject | [PATCH] implement on-chip Coherent memory API for DMA | From | James Bottomley <> | Date | 30 Jun 2004 21:49:22 -0500 |
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This just adds the description and the skeleton null implementation
James
# This is a BitKeeper generated diff -Nru style patch. # # ChangeSet # 2004/06/30 21:02:11-05:00 jejb@mulgrave.(none) # Add dma_declare_coherent_memory() API # # This adds the description and a null prototype. # # include/linux/dma-mapping.h # 2004/06/30 21:01:43-05:00 jejb@mulgrave.(none) +26 -0 # Add dma_declare_coherent_memory() API # # Documentation/DMA-API.txt # 2004/06/30 21:01:43-05:00 jejb@mulgrave.(none) +79 -0 # Add dma_declare_coherent_memory() API # diff -Nru a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt --- a/Documentation/DMA-API.txt 2004-06-30 21:45:21 -05:00 +++ b/Documentation/DMA-API.txt 2004-06-30 21:45:21 -05:00 @@ -444,4 +444,83 @@ continuing on for size. Again, you *must* observe the cache line boundaries when doing this. +int +dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr, + dma_addr_t device_addr, size_t size, int + flags) + + +Declare region of memory to be handed out by dma_alloc_coherent when +it's asked for coherent memory for this device. + +bus_addr is the physical address to which the memory is currently +assigned in the bus responding region (this will be used by the +platform to perform the mapping) + +device_addr is the physical address the device needs to be programmed +with actually to address this memory (this will be handed out as the +dma_addr_t in dma_alloc_coherent()) + +size is the size of the area (must be multiples of PAGE_SIZE). + +flags can be or'd together and are + +DMA_MEMORY_MAP - request that the memory returned from +dma_alloc_coherent() be directly writeable. + +DMA_MEMORY_IO - request that the memory returned from +dma_alloc_coherent() be addressable using read/write/memcpy_toio etc. + +One or both of these flags must be present + +DMA_MEMORY_INCLUDES_CHILDREN - make the declared memory be allocated by +dma_alloc_coherent of any child devices of this one (for memory residing +on a bridge). + +DMA_MEMORY_EXCLUSIVE - only allocate memory from the declared regions. +Do not allow dma_alloc_coherent() to fall back to system memory when +it's out of memory in the declared region. + +The return value will be either DMA_MEMORY_MAP or DMA_MEMORY_IO and +must correspond to a passed in flag (i.e. no returning DMA_MEMORY_IO +if only DMA_MEMORY_MAP were passed in) for success or zero for +failure. + +Note, for DMA_MEMORY_IO returns, all subsequent memory returned by +dma_alloc_coherent() may no longer be accessed directly, but instead +must be accessed using the correct bus functions. If your driver +isn't prepared to handle this contingency, it should not specify +DMA_MEMORY_IO in the input flags. + +As a simplification for the platforms, only *one* such region of +memory may be declared per device. + +For reasons of efficiency, most platforms choose to track the declared +region only at the granularity of a page. For smaller allocations, +you should use the dma_pool() API. + +void +dma_release_declared_memory(struct device *dev) + +Remove the memory region previously declared from the system. This +API performs *no* in-use checking for this region and will return +unconditionally having removed all the required structures. It is the +drivers job to ensure that no parts of this memory region are +currently in use. + +void * +dma_mark_declared_memory_occupied(struct device *dev, + dma_addr_t device_addr, size_t size) + +This is used to occupy specific regions of the declared space +(dma_alloc_coherent() will hand out the first free region it finds). + +device_addr is the *device* address of the region requested + +size is the size (and should be a page sized multiple). + +The return value will be either a pointer to the processor virtual +address of the memory, or an error (via PTR_ERR()) if any part of the +region is occupied. + diff -Nru a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h --- a/include/linux/dma-mapping.h 2004-06-30 21:45:21 -05:00 +++ b/include/linux/dma-mapping.h 2004-06-30 21:45:22 -05:00 @@ -42,6 +42,32 @@ } #endif +/* flags for the coherent memory api */ +#define DMA_MEMORY_MAP 0x01 +#define DMA_MEMORY_IO 0x02 +#define DMA_MEMORY_INCLUDES_CHILDREN 0x04 +#define DMA_MEMORY_EXCLUSIVE 0x08 + +#ifndef ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY +static inline int +dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr, + dma_addr_t device_addr, size_t size, int flags) +{ + return 0; +} + +static inline void +dma_release_declared_memory(struct device *dev) +{ +} + +void *dma_mark_declared_memory_occupied(struct device *dev, + dma_addr_t device_addr, size_t size) +{ + return ERR_PTR(-EBUSY); +} +#endif + #endif
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