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From:   Guo Ren <guoren@kernel.org>
Date:   Thu, 16 Sep 2021 09:32:41 +0800
Message-ID: <CAJF2gTSgbmff7aTjwTD+rhQroWeaXfjepGeEAmooBV6d4u70kg@mail.gmail.com>
Subject: Re: [RFC PATCH V4 4/6] RISC-V: Implement arch_sync_dma* functions
To:     Christoph Hellwig <hch@lst.de>
Cc:     Anup Patel <anup.patel@wdc.com>, Atish Patra <atish.patra@wdc.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        =?UTF-8?Q?Christoph_M=C3=BCllner?= <christoph.muellner@vrull.eu>,
        Philipp Tomsich <philipp.tomsich@vrull.eu>,
        liush <liush@allwinnertech.com>, wefu@redhat.com,
        =?UTF-8?B?V2VpIFd1ICjlkLTkvJ8p?= <lazyparser@gmail.com>,
        Drew Fustini <drew@beagleboard.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        taiten.peng@canonical.com, aniket.ponkshe@canonical.com,
        heinrich.schuchardt@canonical.com, gordan.markus@canonical.com
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On Wed, Sep 15, 2021 at 3:50 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Sat, Sep 11, 2021 at 05:21:37PM +0800, guoren@kernel.org wrote:
> > +static void __dma_sync(phys_addr_t paddr, size_t size, enum dma_data_direction dir)
> > +{
> > +     if ((dir == DMA_FROM_DEVICE) && (dma_cache_sync->cache_invalidate))
> > +             dma_cache_sync->cache_invalidate(paddr, size);
> > +     else if ((dir == DMA_TO_DEVICE) && (dma_cache_sync->cache_clean))
> > +             dma_cache_sync->cache_clean(paddr, size);
> > +     else if ((dir == DMA_BIDIRECTIONAL) && dma_cache_sync->cache_flush)
> > +             dma_cache_sync->cache_flush(paddr, size);
> > +}
>
> Despite various snipplets this is a still pretty much the broken previous
> versions.  These need to use the CMO instructions directly which are
> about to go into review, and then your SBI can trap on those can call
> whatever non-standard mess you're using.
I think you mean put an ALTERNATIVE slot in the prologue of __dma_sync?

#define ALT_DMA_SYNC()                                           \
asm(ALTERNATIVE(".rept 64\n nop\n .endr\n", "<vendor code>",
XXX_VENDOR_ID,        \
                ERRATA_XXX, CONFIG_ERRATA_XXX)  \
                : : : "memory")

static void __dma_sync(phys_addr_t paddr, size_t size, enum
dma_data_direction dir)
{
        ALT_DMA_SYNC();

        /* future cmo codes */
}


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/