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    Subject[PATCH v8 07/26] dmaengine: dw-edma: Add CPU to PCIe bus address translation
    Date
    Starting from commit 9575632052ba ("dmaengine: make slave address
    physical") the source and destination addresses of the DMA-slave device
    have been converted to being defined in CPU address space. It's DMA-device
    driver responsibility to properly convert them to the reachable DMA bus
    spaces. In case of the DW eDMA device, the source or destination
    peripheral (slave) devices reside PCIe bus space. Thus we need to perform
    the PCIe Host/EP windows-based (i.e. ranges DT-property) addresses
    translation otherwise the eDMA transactions won't work as expected (or can
    be even harmful) in case if the CPU and PCIe address spaces don't match.

    Note 1. Even though the DMA interleaved template has both source and
    destination addresses declared of dma_addr_t type only CPU memory range is
    supposed to be mapped in a way so to be seen by the DMA device since it's
    a subject of the DMA getting towards the system side. The device part must
    not be mapped since slave device resides in the PCIe bus space, which
    isn't affected by IOMMUs or iATU translations. DW PCIe eDMA generates
    corresponding MWr/MRd TLPs on its own.

    Note 2. This functionality is mainly required for the remote eDMA setup
    since the CPU address must be manually translated into the PCIe bus space
    before being written to LLI.{SAR,DAR}. If eDMA is embedded into the
    locally accessible DW PCIe RP/EP software-based translation isn't required
    since it will be done by hardware by means of the Outbound iATU as long as
    the DMA_BYPASS flag is cleared. If the later flag is set or there is no
    Outbound iATU entry found to which the SAR or DAR falls in (for Read and
    Write channel respectfully), there won't be any translation performed but
    DMA will proceed with the corresponding source/destination address as is.

    Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
    Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
    Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
    Acked-by: Vinod Koul <vkoul@kernel.org>
    ---
    drivers/dma/dw-edma/dw-edma-core.c | 18 +++++++++++++++++-
    include/linux/dma/edma.h | 15 +++++++++++++++
    2 files changed, 32 insertions(+), 1 deletion(-)

    diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
    index d5c4192141ef..6c9f95a8e397 100644
    --- a/drivers/dma/dw-edma/dw-edma-core.c
    +++ b/drivers/dma/dw-edma/dw-edma-core.c
    @@ -39,6 +39,17 @@ struct dw_edma_desc *vd2dw_edma_desc(struct virt_dma_desc *vd)
    return container_of(vd, struct dw_edma_desc, vd);
    }

    +static inline
    +u64 dw_edma_get_pci_address(struct dw_edma_chan *chan, phys_addr_t cpu_addr)
    +{
    + struct dw_edma_chip *chip = chan->dw->chip;
    +
    + if (chip->ops->pci_address)
    + return chip->ops->pci_address(chip->dev, cpu_addr);
    +
    + return cpu_addr;
    +}
    +
    static struct dw_edma_burst *dw_edma_alloc_burst(struct dw_edma_chunk *chunk)
    {
    struct dw_edma_burst *burst;
    @@ -327,11 +338,11 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
    {
    struct dw_edma_chan *chan = dchan2dw_edma_chan(xfer->dchan);
    enum dma_transfer_direction dir = xfer->direction;
    - phys_addr_t src_addr, dst_addr;
    struct scatterlist *sg = NULL;
    struct dw_edma_chunk *chunk;
    struct dw_edma_burst *burst;
    struct dw_edma_desc *desc;
    + u64 src_addr, dst_addr;
    size_t fsz = 0;
    u32 cnt = 0;
    int i;
    @@ -406,6 +417,11 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
    dst_addr = chan->config.dst_addr;
    }

    + if (dir == DMA_DEV_TO_MEM)
    + src_addr = dw_edma_get_pci_address(chan, (phys_addr_t)src_addr);
    + else
    + dst_addr = dw_edma_get_pci_address(chan, (phys_addr_t)dst_addr);
    +
    if (xfer->type == EDMA_XFER_CYCLIC) {
    cnt = xfer->xfer.cyclic.cnt;
    } else if (xfer->type == EDMA_XFER_SCATTER_GATHER) {
    diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
    index a864978ddd27..380a0a3e251f 100644
    --- a/include/linux/dma/edma.h
    +++ b/include/linux/dma/edma.h
    @@ -23,8 +23,23 @@ struct dw_edma_region {
    size_t sz;
    };

    +/**
    + * struct dw_edma_core_ops - platform-specific eDMA methods
    + * @irq_vector: Get IRQ number of the passed eDMA channel. Note the
    + * method accepts the channel id in the end-to-end
    + * numbering with the eDMA write channels being placed
    + * first in the row.
    + * @pci_address: Get PCIe bus address corresponding to the passed CPU
    + * address. Note there is no need in specifying this
    + * function if the address translation is performed by
    + * the DW PCIe RP/EP controller with the DW eDMA device in
    + * subject and DMA_BYPASS isn't set for all the outbound
    + * iATU windows. That will be done by the controller
    + * automatically.
    + */
    struct dw_edma_core_ops {
    int (*irq_vector)(struct device *dev, unsigned int nr);
    + u64 (*pci_address)(struct device *dev, phys_addr_t cpu_addr);
    };

    enum dw_edma_map_format {
    --
    2.38.1

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