Hi Geert,
> Subject: Re: [PATCH v3] dmaengine: sh: rz-dmac: Add device_synchronize
> callback
>
> Hi Biju,
>
> On Thu, Jul 21, 2022 at 4:49 PM Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> wrote:
> > Some on-chip peripheral modules(for eg:- rspi) on RZ/G2L SoC use the
> > same signal for both interrupt and DMA transfer requests.
> > The signal works as a DMA transfer request signal by setting DMARS,
> > and subsequent interrupt requests to the interrupt controller are
> > masked.
> >
> > We can re-enable the interrupt by clearing the DMARS.
> >
> > This patch adds device_synchronize callback for clearing DMARS and
> > thereby allowing DMA consumers to switch to interrupt mode.
> >
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > ---
> > v2->v3:
> > * Fixed commit description
> > * Added check if the DMA operation has been completed or terminated,
> > and wait (sleep) if needed.
>
> Thanks for the uodate!
>
> > --- a/drivers/dma/sh/rz-dmac.c
> > +++ b/drivers/dma/sh/rz-dmac.c
> > @@ -12,6 +12,7 @@
> > #include <linux/dma-mapping.h>
> > #include <linux/dmaengine.h>
> > #include <linux/interrupt.h>
> > +#include <linux/iopoll.h>
> > #include <linux/list.h>
> > #include <linux/module.h>
> > #include <linux/of.h>
> > @@ -630,6 +631,21 @@ static void rz_dmac_virt_desc_free(struct
> virt_dma_desc *vd)
> > */
> > }
> >
> > +static void rz_dmac_device_synchronize(struct dma_chan *chan) {
> > + struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> > + struct rz_dmac *dmac = to_rz_dmac(chan->device);
> > + u32 chstat;
> > + int ret;
> > +
> > + ret = read_poll_timeout(rz_dmac_ch_readl, chstat, !(chstat &
> CHSTAT_EN),
> > + 10, 1000, false, channel, CHSTAT, 1);
>
> Isn't 1000 µs = 1 ms a bit short?
> IIUIC, I can submit a DMA operation for transfering a 64 KiB (or larger)
> block, and call dmaengine_synchronize() immediately after that?
Will increase to 100 msec?? is it ok?
Cheers,
biju
>
> > + if (ret < 0)
> > + dev_warn(dmac->dev, "DMA Timeout");
> > +
> > + rz_dmac_set_dmars_register(dmac, channel->index, 0); }
> > +
> > /*
> > * ------------------------------------------------------------------
> -----------
> > * IRQ handling
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-
> m68k.org
>
> 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
