Hello,
This is one more respin of the patches which add support for creating reserved memory regions defined in device tree. The last attempt (http://lists.linaro.org/pipermail/linaro-mm-sig/2014-February/003738.html) ended in merging only half of the code, so right now we have complete documentation merged and only basic code, which implements a half of it is written in the documentation. Although the merged patches allow to reserve memory, there is no way of using it for devices and drivers.
This situation makes CMA rather useless, as the main architecture (ARM), which used it, has been converted from board-file based system initialization to device tree. Thus there is no place to use direct calls to dma_declare_contiguous() and some new solution, which bases on device tree, is urgently needed.
This patch series fixes this issue. It provides two, already widely discussed and already present in the kernel, drivers for reserved memory: first based on DMA-coherent allocator, second using Contiguous Memory Allocator. The first one nicely implements typical 'carved out' reserved memory way of allocating contiguous buffers in a kernel-style way. The memory is used exclusively by devices assigned to the given memory region. The second one allows to reuse reserved memory for movable kernel pages (like disk buffers, anonymous memory) and migrates it out when device to allocates contiguous memory buffer. Both driver provides memory buffers via standard dma-mapping API.
The patches have been rebased on top of latest CMA and mm changes merged to akmp kernel tree.
To define a 64MiB CMA region following node is needed:
multimedia_reserved: multimedia_mem_region { compatible = "shared-dma-pool"; reusable; size = <0x4000000>; alignment = <0x400000>; };
Similarly, one can define 64MiB region with DMA coherent memory:
multimedia_reserved: multimedia_mem_region { compatible = "shared-dma-pool"; no-map; size = <0x4000000>; alignment = <0x400000>; };
Then the defined region can be assigned to devices:
scaler: scaler@12500000 { memory-region = <&multimedia_reserved>; /* ... */ }; codec: codec@12600000 { memory-region = <&multimedia_reserved>; /* ... */ };
Best regards Marek Szyprowski Samsung R&D Institute Poland
Changes since v1: (http://www.spinics.net/lists/arm-kernel/msg343702.html) - fixed possible memory leak in case of reserved memory allocation failure (thanks to Joonsoo Kim)
Changes since the version posted in '[PATCH v6 00/11] reserved-memory regions/CMA in devicetree, again' thread http://lists.linaro.org/pipermail/linaro-mm-sig/2014-February/003738.html: - rebased on top of '[PATCH v3 -next 0/9] CMA: generalize CMA reserved area management code' patch series on v3.16-rc3 - improved dma-coherent driver, now it correctly handles assigning more than one device to the given memory region
Patch summary:
Marek Szyprowski (4): drivers: of: add automated assignment of reserved regions to client devices drivers: of: initialize and assign reserved memory to newly created devices drivers: dma-coherent: add initialization from device tree drivers: dma-contiguous: add initialization from device tree
drivers/base/dma-coherent.c | 40 +++++++++++++++++++++++ drivers/base/dma-contiguous.c | 60 +++++++++++++++++++++++++++++++++++ drivers/of/of_reserved_mem.c | 70 +++++++++++++++++++++++++++++++++++++++++ drivers/of/platform.c | 7 +++++ include/linux/cma.h | 3 ++ include/linux/of_reserved_mem.h | 7 +++++ mm/cma.c | 62 +++++++++++++++++++++++++++++------- 7 files changed, 238 insertions(+), 11 deletions(-)