On Wed, Mar 09, 2022 at 03:12:02PM -0600, Frank Li wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
>
> The "direction" member of the "dma_slave_config" structure is deprecated.
> The clients no longer use this field to specify the direction of the slave
> channel. But in the eDMA core, this field is used to differentiate between the
> Root complex (remote) and Endpoint (local) DMA accesses.
>
> Nevertheless, we can't differentiate between local and remote accesses without
> a dedicated flag. So let's get rid of the old check and add a new check for
> verifying the DMA operation between local and remote memory instead.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> ---
> no chang between v1 to v4
> drivers/dma/dw-edma/dw-edma-core.c | 17 ++---------------
> 1 file changed, 2 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index 507f08db1aad3..47c6a52929fcd 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -341,22 +341,9 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
> if (!chan->configured)
> return NULL;
>
> - switch (chan->config.direction) {
> - case DMA_DEV_TO_MEM: /* local DMA */
> - if (dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_READ)
> - break;
> - return NULL;
> - case DMA_MEM_TO_DEV: /* local DMA */
> - if (dir == DMA_MEM_TO_DEV && chan->dir == EDMA_DIR_WRITE)
> - break;
> + /* eDMA supports only read and write between local and remote memory */
The comment is a bit confusing because both cases are named as
"memory" while the permitted directions contains DEV-part, which
means "device". What I would suggest to write here is something like:
"DW eDMA supports transferring data from/to the CPU/Application memory
to/from the PCIe link partner device by injecting the PCIe MWr/MRd TLPs."
-Sergey
> + if (dir != DMA_DEV_TO_MEM && dir != DMA_MEM_TO_DEV)
> return NULL;
> - default: /* remote DMA */
> - if (dir == DMA_MEM_TO_DEV && chan->dir == EDMA_DIR_READ)
> - break;
> - if (dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_WRITE)
> - break;
> - return NULL;
> - }
>
> if (xfer->type == EDMA_XFER_CYCLIC) {
> if (!xfer->xfer.cyclic.len || !xfer->xfer.cyclic.cnt)
> --
> 2.24.0.rc1
>
