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SubjectRe: [PATCH v1] coresight: tmc-etr: Speed up for bounce buffer in flat mode
Hi all,

On Sat, Jul 10, 2021 at 01:00:46PM +0800, Leo Yan wrote:

[...]

> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -21,6 +21,7 @@
>
> struct etr_flat_buf {
> struct device *dev;
> + struct page *pages;
> dma_addr_t daddr;
> void *vaddr;
> size_t size;
> @@ -600,6 +601,7 @@ static int tmc_etr_alloc_flat_buf(struct tmc_drvdata *drvdata,
> {
> struct etr_flat_buf *flat_buf;
> struct device *real_dev = drvdata->csdev->dev.parent;
> + ssize_t aligned_size;
>
> /* We cannot reuse existing pages for flat buf */
> if (pages)
> @@ -609,12 +611,17 @@ static int tmc_etr_alloc_flat_buf(struct tmc_drvdata *drvdata,
> if (!flat_buf)
> return -ENOMEM;
>
> - flat_buf->vaddr = dma_alloc_coherent(real_dev, etr_buf->size,
> - &flat_buf->daddr, GFP_KERNEL);
> - if (!flat_buf->vaddr) {
> - kfree(flat_buf);
> - return -ENOMEM;
> - }
> + aligned_size = PAGE_ALIGN(etr_buf->size);
> + flat_buf->pages = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO,
> + get_order(aligned_size));
> + if (!flat_buf->pages)
> + goto fail_alloc_pages;
> +
> + flat_buf->vaddr = page_address(flat_buf->pages);
> + flat_buf->daddr = dma_map_page(real_dev, flat_buf->pages, 0,
> + aligned_size, DMA_FROM_DEVICE);
> + if (dma_mapping_error(real_dev, flat_buf->daddr))
> + goto fail_dma_map_page;
>
> flat_buf->size = etr_buf->size;
> flat_buf->dev = &drvdata->csdev->dev;
> @@ -622,23 +629,34 @@ static int tmc_etr_alloc_flat_buf(struct tmc_drvdata *drvdata,
> etr_buf->mode = ETR_MODE_FLAT;
> etr_buf->private = flat_buf;
> return 0;
> +
> +fail_dma_map_page:
> + __free_pages(flat_buf->pages, get_order(aligned_size));
> +fail_alloc_pages:
> + kfree(flat_buf);
> + return -ENOMEM;
> }
>
> static void tmc_etr_free_flat_buf(struct etr_buf *etr_buf)
> {
> struct etr_flat_buf *flat_buf = etr_buf->private;
>
> - if (flat_buf && flat_buf->daddr) {
> + if (flat_buf && flat_buf->vaddr) {

I found here I introduced an unexpected change for checking
"flat_buf->vaddr", we should still check "flat_buf->daddr".

Sent patch v2 to address this issue; please directly review patch
v2.

Thanks,
Leo

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