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

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Message-ID: <CACRpkdZdnTX4-jnnXZveXxwOg76yH4Zyoa-ZSGeC7KzOnn+6Lg@mail.gmail.com>
Date:   Fri, 31 Mar 2023 11:10:44 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        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>, Guo Ren <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>,
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        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
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        Max Filippov <jcmvbkbc@...il.com>,
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        Conor Dooley <conor.dooley@...rochip.com>,
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Subject: Re: [PATCH 17/21] ARM: dma-mapping: use arch_sync_dma_for_{device,cpu}()
 internally

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?

> 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>

Yours,
Linus Walleij