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

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Date: Mon, 9 Oct 2023 17:45:59 +0100
From: Robin Murphy <robin.murphy@....com>
To: Christoph Hellwig <hch@....de>, Geert Uytterhoeven <geert@...ux-m68k.org>
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 09/10/2023 1:48 pm, Christoph Hellwig wrote:
> On Mon, Oct 09, 2023 at 01:10:26PM +0200, Geert Uytterhoeven wrote:
>> 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.

Bleh, guess I should have known better than to trust my Monday morning 
memory without double-checking the code :)

> Yeah, and we'll basically need to split RISCV_DMA_NONCOHERENT into
> an option for each type of non-coherent support.  This is why we
> should never have added support for any of the non-standard versions,
> as it's turning into a giant mess.

Indeed the main point I was trying to get at is for ARCH_R9A07G043 (or 
rather possibly ERRATA_ANDES_CMO) to not select RISCV_DMA_NONCOHERENT in 
its current form, since that ending up selecting DMA_DIRECT_REMAP on a 
platform which can't support it is the thing that's most obviously wrong.

Thanks,
Robin.