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

[Guo Ren]

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]?

[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/