linux-kernel - Re: [PATCH 17/21] ARM: dma-mapping: use arch_sync_dma_for

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Message-Id: <f3637818-7528-4564-a208-6e587efd7128@app.fastmail.com>
Date:   Fri, 31 Mar 2023 14:48:34 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Linus Walleij" <linus.walleij@...aro.org>,
        "Arnd Bergmann" <arnd@...nel.org>
Cc:     linux-kernel@...r.kernel.org, "Vineet Gupta" <vgupta@...nel.org>,
        "Russell King" <linux@...linux.org.uk>,
        "Neil Armstrong" <neil.armstrong@...aro.org>,
        "Catalin Marinas" <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>, guoren <guoren@...nel.org>,
        "Brian Cain" <bcain@...cinc.com>,
        "Geert Uytterhoeven" <geert@...ux-m68k.org>,
        "Michal Simek" <monstr@...str.eu>,
        "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
        "Dinh Nguyen" <dinguyen@...nel.org>,
        "Stafford Horne" <shorne@...il.com>,
        "Helge Deller" <deller@....de>,
        "Michael Ellerman" <mpe@...erman.id.au>,
        "Christophe Leroy" <christophe.leroy@...roup.eu>,
        "Paul Walmsley" <paul.walmsley@...ive.com>,
        "Palmer Dabbelt" <palmer@...belt.com>,
        "Rich Felker" <dalias@...c.org>,
        "John Paul Adrian Glaubitz" <glaubitz@...sik.fu-berlin.de>,
        "David S . Miller" <davem@...emloft.net>,
        "Max Filippov" <jcmvbkbc@...il.com>,
        "Christoph Hellwig" <hch@....de>,
        "Robin Murphy" <robin.murphy@....com>,
        "Lad, Prabhakar" <prabhakar.mahadev-lad.rj@...renesas.com>,
        "Conor.Dooley" <conor.dooley@...rochip.com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        "linux-oxnas@...ups.io" <linux-oxnas@...ups.io>,
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        sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH 17/21] ARM: dma-mapping: use arch_sync_dma_for_{device,cpu}()
 internally

On Fri, Mar 31, 2023, at 11:10, Linus Walleij wrote:
> On Mon, Mar 27, 2023 at 2:16 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
>> From: Arnd Bergmann <arnd@...db.de>
>>
>> The arm specific iommu code in dma-mapping.c uses the page+offset based
>> __dma_page_cpu_to_dev()/__dma_page_dev_to_cpu() helpers in place of the
>> phys_addr_t based arch_sync_dma_for_device()/arch_sync_dma_for_cpu()
>> wrappers around the.
>
> Broken sentence?

I've changed s/the/them/ now, at least I think that's what I meant to
write in the first place.

>> In order to be able to move the latter part set of functions into
>> common code, change the iommu implementation to use them directly
>> and remove the internal ones as a separate interface.
>>
>> As page+offset and phys_address are equivalent, but are used in
>> different parts of the code here, this allows removing some of
>> the conversion but adds them elsewhere.
>>
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> Looks good to me, took me some time to verify and understand
> the open-coded version of PFN_UP() and this refactoring alone
> makes the patch highly valuable.
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Thanks!

    ARnd