linux-kernel - Re: [RFC PATCH V4 3/6] RISC-V: Support a new config option for non-coherent DMA

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Message-ID: <CAJF2gTRS=6i6zgdM8-WsdrzbiSrQkrmu+Xx-h6D4puKZqu1ruQ@mail.gmail.com>
Date:   Thu, 16 Sep 2021 14:09:35 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Atish Patra <atishp@...shpatra.org>
Cc:     Christoph Hellwig <hch@....de>, Anup Patel <anup.patel@....com>,
        Atish Patra <atish.patra@....com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Christoph Müllner <christoph.muellner@...ll.eu>,
        Philipp Tomsich <philipp.tomsich@...ll.eu>,
        liush <liush@...winnertech.com>, wefu@...hat.com,
        Wei Wu (吴伟) <lazyparser@...il.com>,
        Drew Fustini <drew@...gleboard.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        taiten.peng@...onical.com, aniket.ponkshe@...onical.com,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        gordan.markus@...onical.com, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [RFC PATCH V4 3/6] RISC-V: Support a new config option for
 non-coherent DMA

On Thu, Sep 16, 2021 at 12:39 PM Atish Patra <atishp@...shpatra.org> wrote:
>
> On Wed, Sep 15, 2021 at 6:21 PM Guo Ren <guoren@...nel.org> wrote:
> >
> > On Wed, Sep 15, 2021 at 3:48 PM Christoph Hellwig <hch@....de> wrote:
> > >
> > > On Sat, Sep 11, 2021 at 05:21:36PM +0800, guoren@...nel.org wrote:
> > > > +     select DMA_GLOBAL_POOL
> > > > +     select DMA_DIRECT_REMAP
> > >
> > > No need to select DMA_GLOBAL_POOL when DMA_DIRECT_REMAP is select.
> > If we want to support PBMT & global_dma_pool both in riscv. Could they
> > work together in arch/riscv with [1]?
>
> We don't have to worry about it as the next version of my series will
> use the simpler
> dma_uncached functionality to support uncached window approach taken
> by starlight socs.
Sounds good, thx.

>
> I was supposed to send it sooner but got busy with PMU stuff and a bad flu :(.
Take good care of yourself and hope you feel better soon.

>
> >
> > [1]: https://lore.kernel.org/lkml/20210818142715.GA10755@lst.de/T/
> >
> > >
> > > Also a patch just to add a option that is not selected and won't build
> > > if selected does not make sense.
> > I just want to rebase on Atish's patch and append DMA_DIRECT_REMAP.
> > Okay, DMA_DIRECT_REMAP & DMA_GLOBAL_POOL should be separated from the
> > patch.
> >
> >
> >
> > --- a/kernel/dma/direct.c
> > +++ b/kernel/dma/direct.c
> > @@ -156,9 +156,14 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> >
> >   if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
> >      !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
> > +    !IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
> >      !dev_is_dma_coherent(dev))
> >   return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);
> >
> > + if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
> > +    !dev_is_dma_coherent(dev))
> > + return dma_alloc_from_global_coherent(dev, size, dma_handle);
> > +
> >   /*
> >   * Remapping or decrypting memory may block. If either is required and
> >   * we can't block, allocate the memory from the atomic pools.
> > @@ -255,11 +260,19 @@ void dma_direct_free(struct device *dev, size_t size,
> >
> >   if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
> >      !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
> > +    !IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
> >      !dev_is_dma_coherent(dev)) {
> >   arch_dma_free(dev, size, cpu_addr, dma_addr, attrs);
> >   return;
> >   }
> >
> > + if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
> > +    !dev_is_dma_coherent(dev)) {
> > + if (!dma_release_from_global_coherent(page_order, cpu_addr))
> > + WARN_ON_ONCE(1);
> > + return;
> > + }
> > +
> > Here CONFIG_DMA_GLOBAL_POOL is independent from CONFIG_DMA_DIRECT_REMAP.
> >
> >   /* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */
> >   if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
> >      dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
> >
> > --
> > Best Regards
> >  Guo Ren
> >
> > ML: https://lore.kernel.org/linux-csky/
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
>
>
>
> --
> Regards,
> Atish


-- 
Best Regards
 Guo Ren

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

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