Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

Geert Uytterhoeven
2023-10-09T11:10:43Z

Hi Robin,

On Mon, Oct 9, 2023 at 12:04 PM Robin Murphy <robin.murphy@arm.com> wrote:
> On 2023-10-09 10:51, Geert Uytterhoeven wrote:
> > On Mon, Oct 9, 2023 at 11:43 AM Christoph Hellwig <hch@lst.de> wrote:
> >> On Mon, Oct 09, 2023 at 11:34:55AM +0200, Geert Uytterhoeven wrote:
> >>> The fix you are referring too is probably commit c1ec4b450ab729e3
> >>> ("soc: renesas: Make ARCH_R9A07G043 (riscv version) depend
> >>> on NONPORTABLE") in next-20231006 and later. It is not yet upstream.
> >>>
> >>> Still, it merely makes ARCH_R9A07G043 (which selects DMA_GLOBAL_POOL)
> >>> depend on ARCH_R9A07G043.
> >>> RISCV_DMA_NONCOHERENT still selects DMA_DIRECT_REMAP, so both can end
> >>> up being enabled.
> >>
> >> Ok, so we need to actually fix this properly. Lad, can you respin
> >> the fix to not select DMA_DIRECT_REMAP, for ARCH_R9A07G043?
> >
> > ARCH_R9A07G043 does not select DMA_DIRECT_REMAP directly,
> > RISCV_DMA_NONCOHERENT does. And there are other users of
> > RISCV_DMA_NONCOHERENT (RISCV_ISA_ZICBOM and ERRATA_THEAD_CMO).
> > Should the selection of DMA_DIRECT_REMAP moved to their users?
>
> No, the selection of DMA_GLOBAL_POOL should be removed from
> RISV_DMA_NONCOHERENT and selected directly by ARCH_R9A07G043 (along with
> any of the other implied symbols it needs). Or if as suggested this
> physical-attribute-remap wackiness is due to show up on more platforms
> as well, maybe have a common config for that which selects
> DMA_GLOBAL_POOL plus the relevant cache maintenance extensions as an
> equivalent to RISCV_DMA_NONCOHERENT, and can itself explicitly depend on
> NONPORTABLE for clarity.

RISCV_DMA_NONCOHERENT does not select DMA_GLOBAL_POOL,
ARCH_R9A07G043 selects DMA_GLOBAL_POOL.
RISCV_DMA_NONCOHERENT does select DMA_DIRECT_REMAP if MMU.

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