On 25-06-18, 11:27, Andrea Merello wrote:
> Whenever a single or cyclic transaction is prepared, the driver
> could eventually split it over several SG descriptors in order
> to deal with the HW maximum transfer length.
>
> This could end up in DMA operations starting from a misaligned
> address. This seems fatal for the HW if DRE is not enabled.
>
> This patch eventually adjusts the transfer size in order to make sure
> all operations start from an aligned address.
>
> Cc: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
> Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
> ---
> Changes in v2:
> - don't introduce copy_mask field, rather rely on already-esistent
> copy_align field. Suggested by Radhey Shyam Pandey
> - reword title
> Changes in v3:
> - fix bug introduced in v2: wrong copy size when DRE is enabled
> use implementation suggested by Radhey Shyam Pandey
> ---
> drivers/dma/xilinx/xilinx_dma.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 27b523530c4a..113d9bf1b6a1 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -1793,6 +1793,16 @@ static struct dma_async_tx_descriptor *xilinx_dma_prep_slave_sg(
> */
> copy = min_t(size_t, sg_dma_len(sg) - sg_used,
> XILINX_DMA_MAX_TRANS_LEN);
> +
> + if ((copy + sg_used < sg_dma_len(sg)) &&
> + chan->xdev->common.copy_align) {
> + /*
> + * If this is not the last descriptor, make sure
> + * the next one will be properly aligned
> + */
> + copy = rounddown(copy,
> + (1 << chan->xdev->common.copy_align));
> + }
> hw = &segment->hw;
>
> /* Fill in the descriptor */
> @@ -1898,6 +1908,16 @@ static struct dma_async_tx_descriptor *xilinx_dma_prep_dma_cyclic(
> */
> copy = min_t(size_t, period_len - sg_used,
> XILINX_DMA_MAX_TRANS_LEN);
> +
> + if ((copy + sg_used < period_len) &&
> + chan->xdev->common.copy_align) {
> + /*
> + * If this is not the last descriptor, make sure
> + * the next one will be properly aligned
> + */
> + copy = rounddown(copy,
> + (1 << chan->xdev->common.copy_align));
> + }
same code pasted twice, can we have a routine for this... perhaps more
code can be made common too
--
~Vinod
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