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    Subject[PATCH v8 08/10] dmaengine: dw: Initialize min and max burst DMA device capability
    Date
    According to the DW APB DMAC data book the minimum burst transaction
    length is 1 and it's true for any version of the controller since
    isn't parametrised in the coreAssembler so can't be changed at the
    IP-core synthesis stage. The maximum burst transaction can vary from
    channel to channel and from controller to controller depending on a
    IP-core parameter the system engineer activated during the IP-core
    synthesis. Let's initialise both min_burst and max_burst members of the
    DMA controller descriptor with extreme values so the DMA clients could
    use them to properly optimize the DMA requests. The channels and
    controller-specific max_burst length initialization will be introduced
    by the follow-up patches.

    Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
    Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

    ---

    Changelog v4:
    - This is a new patch suggested by Andy.

    Changelog v5:
    - Introduce macro with extreme min and max burst length supported by the
    DW DMA controller.
    - Initialize max_burst length capability with extreme burst length supported
    by the DW DMAC IP-core.
    ---
    drivers/dma/dw/core.c | 2 ++
    include/linux/platform_data/dma-dw.h | 2 ++
    2 files changed, 4 insertions(+)

    diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
    index fb95920c429e..afe5a2e465af 100644
    --- a/drivers/dma/dw/core.c
    +++ b/drivers/dma/dw/core.c
    @@ -1223,6 +1223,8 @@ int do_dma_probe(struct dw_dma_chip *chip)
    dw->dma.device_issue_pending = dwc_issue_pending;

    /* DMA capabilities */
    + dw->dma.min_burst = DW_DMA_MIN_BURST;
    + dw->dma.max_burst = DW_DMA_MAX_BURST;
    dw->dma.src_addr_widths = DW_DMA_BUSWIDTHS;
    dw->dma.dst_addr_widths = DW_DMA_BUSWIDTHS;
    dw->dma.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV) |
    diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h
    index f3eaf9ec00a1..369e41e9dcc9 100644
    --- a/include/linux/platform_data/dma-dw.h
    +++ b/include/linux/platform_data/dma-dw.h
    @@ -12,6 +12,8 @@

    #define DW_DMA_MAX_NR_MASTERS 4
    #define DW_DMA_MAX_NR_CHANNELS 8
    +#define DW_DMA_MIN_BURST 1
    +#define DW_DMA_MAX_BURST 256

    /**
    * struct dw_dma_slave - Controller-specific information about a slave
    --
    2.26.2
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