Re: [PATCH 03/44] dmaengine: ioat: don't use DMA_ERROR_CODE

From: Alexander Duyck
Date: Fri Jun 16 2017 - 16:40:42 EST


On Fri, Jun 16, 2017 at 11:10 AM, Christoph Hellwig <hch@xxxxxx> wrote:
> DMA_ERROR_CODE is not a public API and will go away. Instead properly
> unwind based on the loop counter.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> Acked-By: Vinod Koul <vinod.koul@xxxxxxxxx>
> ---
> drivers/dma/ioat/init.c | 24 +++++++-----------------
> 1 file changed, 7 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/dma/ioat/init.c b/drivers/dma/ioat/init.c
> index 6ad4384b3fa8..ed8ed1192775 100644
> --- a/drivers/dma/ioat/init.c
> +++ b/drivers/dma/ioat/init.c
> @@ -839,8 +839,6 @@ static int ioat_xor_val_self_test(struct ioatdma_device *ioat_dma)
> goto free_resources;
> }
>
> - for (i = 0; i < IOAT_NUM_SRC_TEST; i++)
> - dma_srcs[i] = DMA_ERROR_CODE;
> for (i = 0; i < IOAT_NUM_SRC_TEST; i++) {
> dma_srcs[i] = dma_map_page(dev, xor_srcs[i], 0, PAGE_SIZE,
> DMA_TO_DEVICE);
> @@ -910,8 +908,6 @@ static int ioat_xor_val_self_test(struct ioatdma_device *ioat_dma)
>
> xor_val_result = 1;
>
> - for (i = 0; i < IOAT_NUM_SRC_TEST + 1; i++)
> - dma_srcs[i] = DMA_ERROR_CODE;
> for (i = 0; i < IOAT_NUM_SRC_TEST + 1; i++) {
> dma_srcs[i] = dma_map_page(dev, xor_val_srcs[i], 0, PAGE_SIZE,
> DMA_TO_DEVICE);
> @@ -965,8 +961,6 @@ static int ioat_xor_val_self_test(struct ioatdma_device *ioat_dma)
> op = IOAT_OP_XOR_VAL;
>
> xor_val_result = 0;
> - for (i = 0; i < IOAT_NUM_SRC_TEST + 1; i++)
> - dma_srcs[i] = DMA_ERROR_CODE;
> for (i = 0; i < IOAT_NUM_SRC_TEST + 1; i++) {
> dma_srcs[i] = dma_map_page(dev, xor_val_srcs[i], 0, PAGE_SIZE,
> DMA_TO_DEVICE);
> @@ -1017,18 +1011,14 @@ static int ioat_xor_val_self_test(struct ioatdma_device *ioat_dma)
> goto free_resources;
> dma_unmap:
> if (op == IOAT_OP_XOR) {
> - if (dest_dma != DMA_ERROR_CODE)
> - dma_unmap_page(dev, dest_dma, PAGE_SIZE,
> - DMA_FROM_DEVICE);
> - for (i = 0; i < IOAT_NUM_SRC_TEST; i++)
> - if (dma_srcs[i] != DMA_ERROR_CODE)
> - dma_unmap_page(dev, dma_srcs[i], PAGE_SIZE,
> - DMA_TO_DEVICE);
> + while (--i >= 0)
> + dma_unmap_page(dev, dma_srcs[i], PAGE_SIZE,
> + DMA_TO_DEVICE);
> + dma_unmap_page(dev, dest_dma, PAGE_SIZE, DMA_FROM_DEVICE);
> } else if (op == IOAT_OP_XOR_VAL) {
> - for (i = 0; i < IOAT_NUM_SRC_TEST + 1; i++)
> - if (dma_srcs[i] != DMA_ERROR_CODE)
> - dma_unmap_page(dev, dma_srcs[i], PAGE_SIZE,
> - DMA_TO_DEVICE);
> + while (--i >= 0)
> + dma_unmap_page(dev, dma_srcs[i], PAGE_SIZE,
> + DMA_TO_DEVICE);

Wouldn't it make more sense to pull out the while loop and just call
dma_unmap_page on dest_dma if "op == IOAT_OP_XOR"? Odds are it is what
the compiler is already generating and will save a few lines of code
so what you end up with is something like:
while (--i >= 0)
dma_unmap_page(dev, dma_srcs[i], PAGE_SIZE, DMA_TO_DEVICE);
if (op == IOAT_OP_XOR)
dma_unmap_page(dev, dest_dma, PAGE_SIZE, DMA_FROM_DEVICE);

> }
> free_resources:
> dma->device_free_chan_resources(dma_chan);
> --
> 2.11.0
>