Re: [PATCH] scsi: gvp11: add module parameter for DMA transfer bit mask

Geert Uytterhoeven
2023-08-30T18:38:06Z

Hi Michael,

On Wed, Aug 30, 2023 at 12:26 AM Michael Schmitz <schmitzmic@gmail.com> wrote:
> On 30/08/23 10:05, Arnd Bergmann wrote:
> > On Tue, Aug 29, 2023, at 17:45, Michael Schmitz wrote:
> >> SCSI boards on Amiga. There now is no way to set a non-default
> >> DMA mask on these boards.
> > It might help to mention here in which cases the default mask
> > is actually wrong.
>
> All I have is:
>
> Probably it's needed on A2000 with an accelerator card and GVP II SCSI,
> to prevent DMA to RAM banks that do not support fast DMA cycles.
>
> from Geert's reply. I can add that. It just did sound a shade
> speculative...

Apparently gvp11_setup() became unused in 2.3.13pre2 (in 1999), when all
*_setup() functions were removed from init/main.c, and some of them were
reimplemented using __setup() in the driver sources where they belonged.

> >> +module_param(gvp11_xfer_mask, int, 0444);
> >> +MODULE_PARM_DESC(gvp11_xfer_mask, "DMA mask (0xff000000 == 24 bit DMA)");
> >> +
> > I think the comment is the wrong way round, it should be
> > 0x00ffffff in this case, which also matches the default
> > mask for ZORRO_PROD_GVP_SERIES_II, in the match table:
> >
> > static struct zorro_device_id gvp11_zorro_tbl[] = {
> > { ZORRO_PROD_GVP_COMBO_030_R3_SCSI, ~0x00ffffff },
> > { ZORRO_PROD_GVP_SERIES_II, ~0x00ffffff },
> > { ZORRO_PROD_GVP_GFORCE_030_SCSI, ~0x01ffffff },
> > { ZORRO_PROD_GVP_A530_SCSI, ~0x01ffffff },
> > { ZORRO_PROD_GVP_COMBO_030_R4_SCSI, ~0x01ffffff },
> > { ZORRO_PROD_GVP_A1291, ~0x07ffffff },
> > { ZORRO_PROD_GVP_GFORCE_040_SCSI_1, ~0x07ffffff },
> > { 0 }
> > };

The default masks above were added (in some other form) in 2.1.91pre1
(in 1998). Before, people had to use gvp11_setup() to do that.

So I think it is safe to assume there is no longer a need to configure
this manually.

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