linux-kernel - Re: dma engine drivers for 2.6.25?

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Date:	Sat, 23 Feb 2008 19:06:06 -0700
From:	"Dan Williams" <dan.j.williams@...el.com>
To:	"Kumar Gala" <galak@...nel.crashing.org>
Cc:	"LKML Kernel" <linux-kernel@...r.kernel.org>,
	"Zhang Wei" <wei.zhang@...escale.com>
Subject: Re: dma engine drivers for 2.6.25?

On Thu, Feb 14, 2008 at 10:29 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> On Thu, Feb 14, 2008 at 8:44 PM, Kumar Gala <galak@...nel.crashing.org> wrote:
>  >
>  >  On Feb 14, 2008, at 12:14 PM, Dan Williams wrote:
>  >
>  >  > On Wed, Feb 13, 2008 at 8:52 PM, Kumar Gala
>  >  > <galak@...nel.crashing.org> wrote:
>  >  >> Dan,
>  >  >>
>  >  >> What's going on with the dma engine drivers for 2.6.25?  We had a
>  >  >> Freescale dma driver from Zhang Wei queued up but seems to have been
>  >  >> lost.
>  >  >
>  >  > I pulled it into my tree and am holding it until Zhang has an
>  >  > opportunity to address the pending review comments [1].  I also did
>  >  > not feel comfortable pushing it to Linus without a PPC maintainer's
>  >  > Acked-by/Reviewed-by.
>  >  >
>  >  > I have attached the version I am carrying.
>  >
>  >  What issues are still open.  I was under the belief that Zhang had
>  >  resolved all the issues.
>  >
>
>  The high priority review item is that the driver performs operation
>  completion callbacks in hardirq context.  Clients of the API assume
>  that callbacks will happen in softirq context.  Of lesser concern is
>  the use of GFP_ATOMIC in fsl_dma_alloc_descriptor.  Other drivers
>  preallocate a small pool of descriptors.
>

Have not received a response, so let's try this the other way.  I took
a closer look and found that my concern should be addressed by the
following one-liner:

diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
index 902e852..cc9a681 100644
--- a/drivers/dma/fsldma.c
+++ b/drivers/dma/fsldma.c
@@ -685,7 +685,6 @@ static irqreturn_t fsl_dma_chan_do_interrupt(int
irq, void *data)
                                "nlndar 0x%016llx\n", (u64)get_cdar(fsl_chan),
                                (u64)get_ndar(fsl_chan));
                stat &= ~FSL_DMA_SR_EOSI;
-               fsl_chan_ld_cleanup(fsl_chan);
        }

        /* If it current transfer is the end-of-transfer,

With your ack I'll push the driver plus this fixlet for the current kernel.

Regards,
Dan
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