From: Leo Yan <leo.yan@linaro.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Mike Leach <mike.leach@linaro.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] coresight: tmc-etr: Speed up for bounce buffer in flat mode
Date: Thu, 2 Sep 2021 20:54:31 +0800 [thread overview]
Message-ID: <20210902125431.GI303522@leoy-ThinkPad-X240s> (raw)
In-Reply-To: <a94acd88-dab9-048d-ed9b-b4cac6c4d794@arm.com>
Hi Robin,
On Wed, Sep 01, 2021 at 09:03:30PM +0100, Robin Murphy wrote:
[...]
> > @@ -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)
> > @@ -609,11 +611,18 @@ 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);
>
> Use dma_alloc_noncoherent() rather than open-coding this - bare
> alloc_pages() has no understanding of DMA masks, and you wouldn't want to
> end up in the worst case of dma_map_page() bounce-buffering your bounce
> buffer...
Will refine the code with dma_alloc_noncoherent(); it's much reliable
than the self writing code.
Thanks a lot for the suggestion!
prev parent reply other threads:[~2021-09-02 12:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-29 13:54 [PATCH v3] coresight: tmc-etr: Speed up for bounce buffer in flat mode Leo Yan
2021-09-01 20:03 ` Robin Murphy
2021-09-02 12:54 ` Leo Yan [this message]
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