Hi Morimoto-san, On Thu, Nov 16, 2017 at 5:33 AM, Kuninori Morimoto <[email protected]> wrote: > From: Kuninori Morimoto <[email protected]>
Thanks for your patch! > DMAC reads data from source device, and buffered it until transferable > size for shink device. Because of this behavoir, DMAC is including sink, behavior > buffered data . > > Now, CHCR DE bit is controlling DMA transfer enable/disable. > > If DE bit was cleared during data transferring, or during buffering, > it will flush buffered data if source device was peripheral device > (The buffered data will be removed if source device was memory). > Because of this behavior, driver should ensure that DE bit is actually > 0 after cleared. clearing > This patch adds new rcar_dmac_chcr_de_barrier() and call it after CHCR > register access. > > Tested-by: Hiroyuki Yokoyama <[email protected]> > Tested-by: Ryo Kodama <[email protected]> > Signed-off-by: Kuninori Morimoto <[email protected]> > --- > drivers/dma/sh/rcar-dmac.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c > index 2b2c7db..16ebd5d 100644 > --- a/drivers/dma/sh/rcar-dmac.c > +++ b/drivers/dma/sh/rcar-dmac.c > @@ -10,6 +10,7 @@ > * published by the Free Software Foundation. > */ > > +#include <linux/delay.h> > #include <linux/dma-mapping.h> > #include <linux/dmaengine.h> > #include <linux/interrupt.h> > @@ -741,6 +742,24 @@ static int rcar_dmac_fill_hwdesc(struct rcar_dmac_chan > *chan, > /* > ----------------------------------------------------------------------------- > * Stop and reset > */ > +static void rcar_dmac_chcr_de_barrier(struct rcar_dmac_chan *chan) > +{ > + u32 chcr; > + int i; unsigned int > + > + /* > + * Ensure that the setting of the DE bit is actually 0 after > + * clearing it. > + */ > + for (i = 0; i < 1024; i++) { > + chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR); > + if (!(chcr & RCAR_DMACHCR_DE)) > + return; > + udelay(1); > + } What's a typical number of loops needed before DE is really cleared? > + > + dev_err(chan->chan.device->dev, "CHCR DE check error\n"); > +} Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected] In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
