Re: [PATCH] serial: sh-sci: submit rx dma the way the DMA driver can handle it

[Wolfram Sang <wsa@the-dreams.de>]

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On Mon, Oct 06, 2014 at 10:55:40AM +0900, Simon Horman wrote:
> On Thu, Oct 02, 2014 at 06:14:08PM +0200, Wolfram Sang wrote:
> > From: Wolfram Sang <wsa+renesas@sang-engineering.com>
> > 
> > The shdmac driver has a problem when one wants to submit two RX
> > descriptors and then use issue_pending on both (like this driver does):
> > 
> > Submit first desc
> > -> channel state after: SHDMA_PM_ESTABLISHED
> > 
> > Submit second desc
> > -> channel state after: SHDMA_PM_PENDING
> > 
> > PENDING here means: "Oh, we will wait until the first desc is finished
> > and then the second desc will be grabbed from the list anyhow"
> > 
> > However, because issue_pending does nothing for states !=
> > SHDMA_PM_ESTABLISHED, nothing ever gets active :(
> > 
> > Since the DMA driver is probably replaced soon anyhow, I decided for the
> > least intrusive workaround which is to use issue_pending on every RX
> > desc. (Yes, setting s->active_rx twice is ugly).
> > 
> > Probably not for upstream! However, this patch restores DMA capability
> > for SCIFA on my Lager board. Sadly, not for SCIF due to interrupt
> > problems still to be investigated.
> > 
> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> 
> Acked-by: Simon Horman <horms+renesas@verge.net.au>
> 
> sh-sci patches usually go via linux-serial@vger.kernel.org and
> Greg Kroah-Hartman <gregkh@linuxfoundation.org>. Could you repost this patch
> with those parties included?

I wanted to send this patch as RFC, but forgot to rename it :) I'd
really like some discussion about it, probably in Düsseldorf even. I am
still not sure this patch should go upstream, but we should talk about
it.

Thanks,

   Wolfram


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