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: <20230330204217.47666-1-prabhakar.mahadev-lad.rj@bp.renesas.com>
 <20230330204217.47666-2-prabhakar.mahadev-lad.rj@bp.renesas.com> <ZCu1tFrQCVe2sgNz@infradead.org>
In-Reply-To: <ZCu1tFrQCVe2sgNz@infradead.org>
From:   "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Date:   Thu, 6 Apr 2023 18:59:22 +0000
Message-ID: <CA+V-a8sn8ai1h9+D-b2+Uj2xGcPOw95ukFPy=T_jL+EjTuqApQ@mail.gmail.com>
Subject: Re: [PATCH v7 1/6] riscv: mm: dma-noncoherent: Switch using function
 pointers for cache management
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Conor Dooley <conor.dooley@microchip.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Heiko Stuebner <heiko@sntech.de>, Guo Ren <guoren@kernel.org>,
        Andrew Jones <ajones@ventanamicro.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Samuel Holland <samuel@sholland.org>,
        linux-riscv@lists.infradead.org, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-renesas-soc@vger.kernel.org,
        Biju Das <biju.das.jz@bp.renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Hi Christoph,

On Tue, Apr 4, 2023 at 6:29=E2=80=AFAM Christoph Hellwig <hch@infradead.org=
> wrote:
>
> On Thu, Mar 30, 2023 at 09:42:12PM +0100, Prabhakar wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> >
> > Currently, selecting which CMOs to use on a given platform is done usin=
g
> > and ALTERNATIVE_X() macro. This was manageable when there were just two
> > CMO implementations, but now that there are more and more platforms com=
ing
> > needing custom CMOs, the use of the ALTERNATIVE_X() macro is unmanageab=
le.
> >
> > To avoid such issues this patch switches to use of function pointers
> > instead of ALTERNATIVE_X() macro for cache management (the only drawbac=
k
> > being performance over the previous approach).
> >
> > void (*clean_range)(unsigned long addr, unsigned long size);
> > void (*inv_range)(unsigned long addr, unsigned long size);
> > void (*flush_range)(unsigned long addr, unsigned long size);
> >
>
> NAK.  Function pointers for somthing high performance as cache
> maintainance is a complete no-go.
>
Ok, I will take the ALTERNATIVE() macro route.

Cheers,
Prabhakar