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	<1290510371-23077-2-git-send-email-jamie@jamieiles.com>
Date: Fri, 3 Dec 2010 15:20:01 -0800
Message-ID: <AANLkTi=jraL77=ix=y5QF9YVTVZ9XGF6AXKEx5yMJW3i@mail.gmail.com>
Subject: Re: [PATCH 1/4] dmaengine/dw_dmac: don't scan descriptors if no xfers
 in progress
From: Dan Williams <dan.j.williams@intel.com>
To: Jamie Iles <jamie@jamieiles.com>
Cc: linux-kernel@vger.kernel.org, Jamie Iles <jamie.iles@picochip.com>,
        hskinnemoen@gmail.com
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[ copying Haavard's new address ]

On Tue, Nov 23, 2010 at 3:06 AM, Jamie Iles <jamie@jamieiles.com> wrote:
> Some hardware (picoChip picoXCell in particular) sometimes has
> the block transfer complete bit being set for a channel after the
> whole transfer has completed. If we don't have any transfers in the
> active list then don't bother to scan the descriptors. This often
> happens in normal operation and doesn't require the channel to be
> reset.
>
> Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Jamie Iles <jamie.iles@picochip.com>
> ---
> ?drivers/dma/dw_dmac.c | ? ?3 +++
> ?1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
> index a3991ab..08c51d4 100644
> --- a/drivers/dma/dw_dmac.c
> +++ b/drivers/dma/dw_dmac.c
> @@ -291,6 +291,9 @@ static void dwc_scan_descriptors(struct dw_dma *dw, struct dw_dma_chan *dwc)
> ? ? ? ? ? ? ? ?return;
> ? ? ? ?}
>
> + ? ? ? ?if (list_empty(&dwc->active_list))
> + ? ? ? ? ? ? ? ?return;
> +
> ? ? ? ?dev_vdbg(chan2dev(&dwc->chan), "scan_descriptors: llp=0x%x\n", llp);
>
> ? ? ? ?list_for_each_entry_safe(desc, _desc, &dwc->active_list, desc_node) {
> --
> 1.7.2.3
>
> --
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