linux-kernel - Re: [PATCH 1/2] sh: dma: fix `dmaor_read_reg`/`dmaor_write

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Date:   Mon, 8 May 2023 13:46:00 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc:     Artur Rojek <contact@...ur-rojek.eu>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Rafael Ignacio Zurita <rafaelignacio.zurita@...il.com>,
        linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] sh: dma: fix `dmaor_read_reg`/`dmaor_write_reg` macros

Hi Adrian,

On Mon, May 8, 2023 at 1:28 PM John Paul Adrian Glaubitz
<glaubitz@...sik.fu-berlin.de> wrote:
> On Mon, 2023-05-08 at 13:20 +0200, Geert Uytterhoeven wrote:
> > Looks like this is still broken on e.g. SH7751R, which has 8 channels,
> > both handled by a single DMAOR register at offset 0x40...
> >
> > While e.g. dma_base_addr() seems to have some provision for this
> > (cfr. the "chan >= 9" (not "8") check), dma_find_base() will fail, as
> > arch/sh/include/cpu-sh4/cpu/dma.h defines SH_DMAC_BASE1.
> > Anyway, that's not new, so I have no objection to your patch.
>
> Was SH7751R broken by 7f47c7189b3e8f19 as well?

I think so.
Before, the code to use 1 or 2 DMA engine relied on the presence of
DMAE1_IRQ, which is/was defined in arch/sh/include/cpu-sh4a/cpu/dma.h,
but not in arch/sh/include/cpu-sh4/cpu/dma.h.

It might be sufficient to fix this by just dropping the SH_DMAC_BASE1
definition from arch/sh/include/cpu-sh4/cpu/dma.h.  I'm actually
wondering why it was added (in commit 71b973a42c545682 ("sh: dma-sh
updates for multi IRQ and new SH-4A CPUs.")), because it looks like
none of the SH4-based (not SH4A!) SoCs have a second base...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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