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

[Atish Patra]

On Wed, Sep 15, 2021 at 6:21 PM Guo Ren <guoren at kernel.org> wrote:
>
> On Wed, Sep 15, 2021 at 3:48 PM Christoph Hellwig <hch at lst.de> wrote:
> >
> > On Sat, Sep 11, 2021 at 05:21:36PM +0800, guoren at kernel.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.

I was supposed to send it sooner but got busy with PMU stuff and a bad flu :(.

>
> [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/
>
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-- 
Regards,
Atish