Make bcm2835 DMA address handling less egregious #6658
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A basic device-specific linear memory mapping was introduced back in
commit ("dma: Take into account dma_pfn_offset") as a single-valued offset
preserved in the device.dma_pfn_offset field, which was initialized for
instance by means of the "dma-ranges" DT property. Afterwards the
functionality was extended to support more than one device-specific region
defined in the device.dma_range_map list of maps. But all of these
improvements concerned a single pointer, page or sg DMA-mapping methods,
while the system resource mapping function turned to miss the
corresponding modification. Thus the dma_direct_map_resource() method now
just casts the CPU physical address to the device DMA address with no
dma-ranges-based mapping taking into account, which is obviously wrong.
Let's fix it by using the phys_to_dma_direct() method to get the
device-specific bus address from the passed memory resource for the case
of the directly mapped DMA.
Fixes: 25f1e18 ("dma: Take into account dma_pfn_offset")
Signed-off-by: Serge Semin <[email protected]>
The commit titled "bcm2835-dma: Derive slave DMA addresses correctly" (now squashed into DMA roll-up) moved the responsibility for calculating DMA addresses to the DMA driver. Unfortunately it committed the sin of using phys_to_dma directly rather than using the approved API, i.e. dma_map_resource. Signed-off-by: Phil Elwell <[email protected]>
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popcornmix
approved these changes
Feb 7, 2025
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Replace calls to
phys_to_dma(and function that belongs to the internals of the DMA framework) withdma_map_resource. Note that this patch does not include matching calls todma_unmap_resourcebecause the dma_device struct does not include a method to release a dma_async_tx_descriptor, requiring other means to decide when it's no longer needed, and because it does nothing if direct DMA is being used - the mapping process is just an address calculation.