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

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Date: Mon, 9 Oct 2023 13:10:26 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Robin Murphy <robin.murphy@....com>
Cc: Christoph Hellwig <hch@....de>, iommu@...ts.linux.dev, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Wei Fang <wei.fang@....com>, 
	Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>, 
	NXP Linux Team <linux-imx@....com>, linux-m68k@...ts.linux-m68k.org, netdev@...r.kernel.org, 
	Jim Quinlan <james.quinlan@...adcom.com>, linux-riscv <linux-riscv@...ts.infradead.org>, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>, 
	"Lad, Prabhakar" <prabhakar.mahadev-lad.rj@...renesas.com>, arm-soc <soc@...nel.org>
Subject: Re: [PATCH 1/6] dma-direct: add depdenencies to CONFIG_DMA_GLOBAL_POOL

Hi Robin,

On Mon, Oct 9, 2023 at 12:04 PM Robin Murphy <robin.murphy@....com> wrote:
> On 2023-10-09 10:51, Geert Uytterhoeven wrote:
> > On Mon, Oct 9, 2023 at 11:43 AM Christoph Hellwig <hch@....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@...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