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

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Message-ID: <1cd44af1-10ac-465a-8d20-e0aa268e036f@arm.com>
Date: Mon, 9 Oct 2023 11:04:09 +0100
From: Robin Murphy <robin.murphy@....com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>, Christoph Hellwig <hch@....de>
Cc: 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

On 2023-10-09 10:51, Geert Uytterhoeven wrote:
> Hi Christoph,
> 
> CC soc
> 
> 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.

Thanks,
Robin.

> Note that the fix is already in soc/for-next, so we need coordination
> with the soc people.
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
>