Hi Sergei,
Thanks for your patch.
On Fri, 2 Aug 2013, Sergei Shtylyov wrote:
> I'm testing SH-Mobile SDHI driver in DMA mode with a new DMA controller
> using
> 'bonnie++' and getting DMA error after which the tmio_mmc_dma.c code falls
> back
> to PIO but all commands time out after that. It turned out that the fallback
> code calls tmio_mmc_enable_dma() with RX/TX channels already freed and
> pointers
> to them cleared, so that the function bails out early instead of clearing the
> DMA bit in the CTL_DMA_ENABLE register. Fixing the RX/TX channel check so
> that
> it takes place only when enabling DMA helps with the PIO fallback.
>
> Signed-off-by: Sergei Shtylyov <sergei.shtyl...@cogentembedded.com>
>
> ---
> The patch is against Chris Ball's 'mmc.git' repo, 'master' branch.
>
> drivers/mmc/host/tmio_mmc_dma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: mmc/drivers/mmc/host/tmio_mmc_dma.c
> ===================================================================
> --- mmc.orig/drivers/mmc/host/tmio_mmc_dma.c
> +++ mmc/drivers/mmc/host/tmio_mmc_dma.c
> @@ -25,7 +25,7 @@
>
> void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable)
> {
> - if (!host->chan_tx || !host->chan_rx)
> + if (enable && !(host->chan_tx && host->chan_rx))
> return;
Ok, I see the problem and this does fix it. But it adds complexity to the
driver - one more condition to an if. Whereas, I think, it can be avoided
if we just move calls to
tmio_mmc_enable_dma(host, false);
in tmio_mmc_start_dma_rx() and tmio_mmc_start_dma_tx() a couple of lines
up - before clearing ->chan_rx and ->chan_tx pointers? That should work
too at no cost. I think that would be a better fix, could you, please,
try?
Thanks
Guennadi
> #if defined(CONFIG_SUPERH) || defined(CONFIG_ARCH_SHMOBILE)
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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