Hi Geert, Thanks for the feedback. > I would add a cpu_relax() to the loop. This routine is being called from soft IRQ context (rx_timer_fn in case of sh-sci). Does it still make sense to add cpu_relax? > BTW, please run scripts/checkpatch.pl on your patches before submission. I did run that and got no warning/error. Am I missing something? Cheers! Hamza -----Original Message----- From: geert.uytterhoeven@xxxxxxxxx [mailto:geert.uytterhoeven@xxxxxxxxx] On Behalf Of Geert Uytterhoeven Sent: Dienstag, 15. September 2015 17:11 To: hamzahfrq.sub@xxxxxxxxx Cc: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>; dmaengine@xxxxxxxxxxxxxxx; Jürg Billeter <j@xxxxxxxxx>; Joe Perches <joe@xxxxxxxxxxx>; Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>; Mark Brown <broonie@xxxxxxxxxx>; Geert Uytterhoeven <geert+renesas@xxxxxxxxx>; Vinod Koul <vinod.koul@xxxxxxxxx>; Farooq, Muhammad (M.HAMZA.) <mfarooq@xxxxxxxxxxx> Subject: Re: [PATCH 1/6] dma: rcar-dma: add wait after stopping dma engine Hi Hamza, On Mon, Sep 14, 2015 at 2:02 PM, <hamzahfrq.sub@xxxxxxxxx> wrote: > DMA engine does not stop instantaneously when transaction is going on > (see datasheet). Wait has been added > > Signed-off-by: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx> Thanks for your patch! > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c > index 7820d07..920f977 100644 > --- a/drivers/dma/sh/rcar-dmac.c > +++ b/drivers/dma/sh/rcar-dmac.c > @@ -716,14 +716,37 @@ static int rcar_dmac_fill_hwdesc(struct > rcar_dmac_chan *chan, > /* ----------------------------------------------------------------------------- > * Stop and reset > */ > +#define NR_READS_TO_WAIT (5) /* number of reads to perform to check DE = 0 */ > +static inline int rcar_dmac_wait_stop(struct rcar_dmac_chan *chan) { > + unsigned int i = 0; > + do { > + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR); > + > + if(!(chcr & RCAR_DMACHCR_DE)) > + return 0; > + dev_dbg(chan->chan.device->dev, "DMA transfer couldn't > + be stopped"); I would add a cpu_relax() to the loop. > + } > + while(++i < NR_READS_TO_WAIT); BTW, please run scripts/checkpatch.pl on your patches before submission. Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx 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 ��.n��������+%������w��{.n��������)�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
