Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230327121317.4081816-1-arnd@kernel.org> <20230327121317.4081816-3-arnd@kernel.org>
In-Reply-To: <20230327121317.4081816-3-arnd@kernel.org>
From:   Max Filippov <jcmvbkbc@gmail.com>
Date:   Mon, 27 Mar 2023 08:42:59 -0700
Message-ID: <CAMo8BfJwjcQxWVW9o6brvBYTgUe9v=QGgs39=_V6Oc9-OKv7Sw@mail.gmail.com>
Subject: Re: [PATCH 02/21] xtensa: dma-mapping: use normal cache invalidation rules
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        Vineet Gupta <vgupta@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
        Brian Cain <bcain@quicinc.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Michal Simek <monstr@monstr.eu>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Dinh Nguyen <dinguyen@kernel.org>,
        Stafford Horne <shorne@gmail.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Rich Felker <dalias@libc.org>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        "David S. Miller" <davem@davemloft.net>,
        Christoph Hellwig <hch@lst.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Conor Dooley <conor.dooley@microchip.com>,
        linux-snps-arc@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-oxnas@groups.io,
        linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,
        linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
        linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
        linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
        linux-xtensa@linux-xtensa.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Mon, Mar 27, 2023 at 5:14=E2=80=AFAM Arnd Bergmann <arnd@kernel.org> wro=
te:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> xtensa is one of the platforms that has both write-back and write-through
> caches, and needs to account for both in its DMA mapping operations.
>
> It does this through a set of operations that is different from any
> architecture. This is not a problem by itself, but it makes it rather
> hard to figure out whether this is correct or not, and to unify this
> implementation with the others.
>
> Change the semantics to the usual ones for non-speculating CPUs:
>
>  - On DMA_TO_DEVICE, call __flush_dcache_range() to perform the
>    writeback even on writethrough caches, where this is a nop.
>
>  - On DMA_FROM_DEVICE, invalidate the mapping before the DMA rather
>    than afterwards.
>
>  - On DMA_BIDIRECTIONAL, combine the pre-writeback with the
>    post-invalidate into a call to __flush_invalidate_dcache_range()
>    that turns into a simple invalidate on writeback caches.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/xtensa/Kconfig                  |  1 -
>  arch/xtensa/include/asm/cacheflush.h |  6 +++---
>  arch/xtensa/kernel/pci-dma.c         | 29 +++++-----------------------
>  3 files changed, 8 insertions(+), 28 deletions(-)

Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>

--=20
Thanks.
-- Max