linux-kernel - Re: [RFC PATCH v3 2/2] soc: renesas: Add L2 cache management for RZ/Five SoC

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Date:   Wed, 2 Nov 2022 00:59:57 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Guo Ren <guoren@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Atish Patra <atishp@...osinc.com>,
        Anup Patel <anup@...infault.org>,
        Andrew Jones <ajones@...tanamicro.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-renesas-soc@...r.kernel.org,
        Biju Das <biju.das.jz@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [RFC PATCH v3 2/2] soc: renesas: Add L2 cache management for
 RZ/Five SoC

Hi Geert,

On Tue, Nov 1, 2022 at 1:38 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Thu, Oct 20, 2022 at 12:02 AM Prabhakar <prabhakar.csengg@...il.com> wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >
> > On the AX45MP core, cache coherency is a specification option so it may
> > not be supported. In this case DMA will fail. As a workaround, firstly we
> > allocate a global dma coherent pool from which DMA allocations are taken
> > and marked as non-cacheable + bufferable using the PMA region as specified
> > in the device tree. Synchronization callbacks are implemented to
> > synchronize when doing DMA transactions.
> >
> > The Andes AX45MP core has a Programmable Physical Memory Attributes (PMA)
> > block that allows dynamic adjustment of memory attributes in the runtime.
> > It contains a configurable amount of PMA entries implemented as CSR
> > registers to control the attributes of memory locations in interest.
> >
> > Below are the memory attributes supported:
> > * Device, Non-bufferable
> > * Device, bufferable
> > * Memory, Non-cacheable, Non-bufferable
> > * Memory, Non-cacheable, Bufferable
> > * Memory, Write-back, No-allocate
> > * Memory, Write-back, Read-allocate
> > * Memory, Write-back, Write-allocate
> > * Memory, Write-back, Read and Write-allocate
> >
> > This patch adds support to configure the memory attributes of the memory
> > regions as passed from the l2 cache node and exposes the cache management
> > ops.
> >
> > More info about PMA (section 10.3):
> > http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf
> >
> > This feature is based on the work posted [0] by Vincent Chen
> > <vincentc@...estech.com> for the Andes AndeStart RISC-V CPU.
> >
> > [0] https://lore.kernel.org/lkml/1540982130-28248-1-git-send-email-vincentc@andestech.com/
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Thanks for your patch!
>
> > --- a/arch/riscv/include/asm/errata_list.h
> > +++ b/arch/riscv/include/asm/errata_list.h
> > @@ -89,6 +89,7 @@ asm volatile(ALTERNATIVE(                                             \
> >  #define ALT_THEAD_PMA(_val)
> >  #endif
> >
> > +#ifdef CONFIG_ERRATA_THEAD_CMO
> >  /*
> >   * dcache.ipa rs1 (invalidate, physical address)
> >   * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> > @@ -143,5 +144,6 @@ asm volatile(ALTERNATIVE_2(                                         \
> >         : "a0")
> >
> >  #endif /* __ASSEMBLY__ */
> > +#endif
>
> FTR, the new #endif should be above the old #endif.
>
> I noticed because after rebasing on top of commit 65e9fb081877a18c
> ("drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head
> C9xx cores") in riscv/for-next, the build failed because the new
> ALT_SBI_PMU_OVERFLOW() definition ended up inside both #endifs,
> instead of between.
>
Thanks for pointing this out.

Cheers,
Prabhakar