From: wangx@marvell•com (Xiang Wang)
To: linux-arm-kernel@lists•infradead.org
Subject: [v3 1/2] dma: mmp_pdma: add support for residue reporting
Date: Fri, 16 Aug 2013 15:57:53 +0800 [thread overview]
Message-ID: <520DDB81.20607@marvell.com> (raw)
In-Reply-To: <1376497189-21298-1-git-send-email-zonque@gmail.com>
On 08/15/2013 12:19 AM, Daniel Mack wrote:
> In order to report the channel's residue, we have to memorize the first
> dma buffer position when the channel is configured.
>
> Signed-off-by: Daniel Mack <zonque@gmail•com>
> ---
> drivers/dma/mmp_pdma.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 43 insertions(+), 2 deletions(-)
>
> +static unsigned int mmp_pdma_residue(struct mmp_pdma_chan *chan)
> +{
> + struct mmp_pdma_desc_sw *sw;
> + u32 curr, done = 0;
> +
> + if (chan->dir == DMA_DEV_TO_MEM)
> + curr = readl(chan->phy->base + DTADR(chan->phy->idx));
One concern for this patch:
If we call dmaengine_tx_status() after dma_do_tasklet at mmp_pdma.c,
chan->phy will most likely to be NULL.
dma_do_tasklet() -> start_pending_queue() -> mmp_pdma_free_phy()
For why do we call dmaengine_tx_status() after a DMA interrupt:
briefly, if we use DMA to handle device trailing bytes, it'll report a
DMA interrupt. We need to get to know how many bytes have been received
in the IRQ handler.
We've discussed about this in the link below:
http://thread.gmane.org/gmane.linux.kernel/1500713
--
Regards,
Xiang
next prev parent reply other threads:[~2013-08-16 7:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-14 16:19 [v3 1/2] dma: mmp_pdma: add support for residue reporting Daniel Mack
2013-08-14 16:23 ` Russell King - ARM Linux
2013-08-15 1:57 ` Chao Xie
2013-08-15 3:44 ` Daniel Mack
2013-08-15 8:08 ` Chao Xie
2013-08-15 18:12 ` Daniel Mack
2013-08-16 2:21 ` Chao Xie
2013-08-16 7:57 ` Xiang Wang [this message]
2013-08-16 15:40 ` Daniel Mack
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