Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 16 Oct 2017 09:14:50 +0200 | Subject | Re: [PATCH] dmaengine: rcar-dmac: read DMATCRB instead of DMATCR for residue |
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Hi Morimoto-san,
On Mon, Oct 16, 2017 at 9:12 AM, Kuninori Morimoto <kuninori.morimoto.gx@renesas.com> wrote: >> > SYS/RT/Audio DMAC have both TCR/TCRB register. >> > Its difference is transfer counter value of read (= TCR) >> > or write (= TCRB). The relationship is like below. >> > >> > TCR TCRB >> > [SOURCE] -> [DMAC] -> [DESTINATION] >> > >> > Thus, we want to read TCRB instead of TCR for residue. >> > Otherwise, Sound Capture has noise after PluseAudio support >> > (= 07b7acb51d2 ("ASoC: rsnd: update pointer more accurate")) >> > >> > Signed-off-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com> >> > [Kuninori: added detail information in log] >> > Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com> > (snip) >> However, shouldn't the register to use depend on the DMA direction? > > I think TCRB is OK for all direction, > but yes, we can care its direction. > I can post v2 patch, if you want. > Geert do you want to care direction ?
Please do. I think in general the .get_residue() callback should return the correct value for both reading and writing.
Thanks!
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
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