switch m68k to use the generic remapping DMA allocator v2

switch m68k to use the generic remapping DMA allocator v2

[Christoph Hellwig]

Hi Geert,

can you take a look at the (untested) patches below?  They convert m68k
to use the generic remapping DMA allocator, which is also used by
arm64 and csky.

Changes since v2:
 - fix kconfig dependencies to properly build on sun3
 - updated a patch description to better explain why we are doing this
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[PATCH 1/2] m68k: use the generic dma coherent remap allocator

[Christoph Hellwig]

This switche to using common code for the DMA allocations, including
potential use of the CMA allocator if configure.  Also add a
comment where the existing behavior seems to be lacking.

Switching to the generic code enables DMA allocations from atomic
context, which is required by the DMA API documentation, and also
adds various other minor features drivers start relying upon.  It
also makes sure we have on tested code base for all architectures
that require uncached pte bits for coherent DMA allocations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/m68k/Kconfig      |  2 ++
 arch/m68k/kernel/dma.c | 59 ++++++++----------------------------------
 2 files changed, 13 insertions(+), 48 deletions(-)

diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 218e037ef901..3a52bf46e043 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -3,10 +3,12 @@ config M68K
 	bool
 	default y
 	select ARCH_32BIT_OFF_T
+	select ARCH_HAS_DMA_MMAP_PGPROT if MMU && !COLDFIRE
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
 	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
 	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_NO_PREEMPT if !COLDFIRE
+	select DMA_DIRECT_REMAP if HAS_DMA && MMU && !COLDFIRE
 	select HAVE_IDE
 	select HAVE_AOUT if MMU
 	select HAVE_DEBUG_BUGVERBOSE
diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
index b4aa853051bd..9c6a350a16d8 100644
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
@@ -18,57 +18,20 @@
 #include <asm/pgalloc.h>
 
 #if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
-
-void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
-		gfp_t flag, unsigned long attrs)
+pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
+		unsigned long attrs)
 {
-	struct page *page, **map;
-	pgprot_t pgprot;
-	void *addr;
-	int i, order;
-
-	pr_debug("dma_alloc_coherent: %d,%x\n", size, flag);
-
-	size = PAGE_ALIGN(size);
-	order = get_order(size);
-
-	page = alloc_pages(flag | __GFP_ZERO, order);
-	if (!page)
-		return NULL;
-
-	*handle = page_to_phys(page);
-	map = kmalloc(sizeof(struct page *) << order, flag & ~__GFP_DMA);
-	if (!map) {
-		__free_pages(page, order);
-		return NULL;
+	/*
+	 * XXX: this doesn't seem to handle the sun3 MMU at all.
+	 */
+	if (CPU_IS_040_OR_060) {
+		pgprot_val(prot) &= ~_PAGE_CACHE040;
+		pgprot_val(prot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
+	} else {
+		pgprot_val(prot) |= _PAGE_NOCACHE030;
 	}
-	split_page(page, order);
-
-	order = 1 << order;
-	size >>= PAGE_SHIFT;
-	map[0] = page;
-	for (i = 1; i < size; i++)
-		map[i] = page + i;
-	for (; i < order; i++)
-		__free_page(page + i);
-	pgprot = __pgprot(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_DIRTY);
-	if (CPU_IS_040_OR_060)
-		pgprot_val(pgprot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
-	else
-		pgprot_val(pgprot) |= _PAGE_NOCACHE030;
-	addr = vmap(map, size, VM_MAP, pgprot);
-	kfree(map);
-
-	return addr;
+	return prot;
 }
-
-void arch_dma_free(struct device *dev, size_t size, void *addr,
-		dma_addr_t handle, unsigned long attrs)
-{
-	pr_debug("dma_free_coherent: %p, %x\n", addr, handle);
-	vfree(addr);
-}
-
 #else
 
 #include <asm/cacheflush.h>
-- 
2.20.1

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Re: [PATCH 1/2] m68k: use the generic dma coherent remap allocator

[Geert Uytterhoeven]

Hi Christoph,

On Tue, Jun 25, 2019 at 11:01 AM Christoph Hellwig <hch@lst.de> wrote:
> This switche to using common code for the DMA allocations, including

switches m68k

> potential use of the CMA allocator if configure.  Also add a

configured

> comment where the existing behavior seems to be lacking.
>
> Switching to the generic code enables DMA allocations from atomic
> context, which is required by the DMA API documentation, and also
> adds various other minor features drivers start relying upon.  It
> also makes sure we have on tested code base for all architectures

a tested code base

> that require uncached pte bits for coherent DMA allocations.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Thanks, applying and queueing for v5.3.

> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c
> @@ -18,57 +18,20 @@
>  #include <asm/pgalloc.h>
>
>  #if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
> -
> -void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> -               gfp_t flag, unsigned long attrs)
> +pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> +               unsigned long attrs)
>  {
> -       struct page *page, **map;
> -       pgprot_t pgprot;
> -       void *addr;
> -       int i, order;
> -
> -       pr_debug("dma_alloc_coherent: %d,%x\n", size, flag);
> -
> -       size = PAGE_ALIGN(size);
> -       order = get_order(size);
> -
> -       page = alloc_pages(flag | __GFP_ZERO, order);
> -       if (!page)
> -               return NULL;
> -
> -       *handle = page_to_phys(page);
> -       map = kmalloc(sizeof(struct page *) << order, flag & ~__GFP_DMA);
> -       if (!map) {
> -               __free_pages(page, order);
> -               return NULL;
> +       /*
> +        * XXX: this doesn't seem to handle the sun3 MMU at all.

Correct.  This file is not compiled on Sun-3, which selects NO_DMA, so
I'll drop the comment while applying.

> +        */
> +       if (CPU_IS_040_OR_060) {
> +               pgprot_val(prot) &= ~_PAGE_CACHE040;
> +               pgprot_val(prot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
> +       } else {
> +               pgprot_val(prot) |= _PAGE_NOCACHE030;
>         }
> -       split_page(page, order);
> -
> -       order = 1 << order;
> -       size >>= PAGE_SHIFT;
> -       map[0] = page;
> -       for (i = 1; i < size; i++)
> -               map[i] = page + i;
> -       for (; i < order; i++)
> -               __free_page(page + i);
> -       pgprot = __pgprot(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_DIRTY);
> -       if (CPU_IS_040_OR_060)
> -               pgprot_val(pgprot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
> -       else
> -               pgprot_val(pgprot) |= _PAGE_NOCACHE030;
> -       addr = vmap(map, size, VM_MAP, pgprot);
> -       kfree(map);
> -
> -       return addr;
> +       return prot;
>  }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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[PATCH 2/2] m68k: implement arch_dma_prep_coherent

[Christoph Hellwig]

When we remap memory as non-cached to be used as a DMA coherent buffer
we should writeback all cache and invalidate the cache lines so that
we make sure we have a clean slate.  Implement this using the
cache_push() helper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/m68k/Kconfig      | 1 +
 arch/m68k/kernel/dma.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 3a52bf46e043..00f5c98a5e05 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -4,6 +4,7 @@ config M68K
 	default y
 	select ARCH_32BIT_OFF_T
 	select ARCH_HAS_DMA_MMAP_PGPROT if MMU && !COLDFIRE
+	select ARCH_HAS_DMA_PREP_COHERENT
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
 	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
 	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
index 9c6a350a16d8..e720e6eed838 100644
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
@@ -18,6 +18,11 @@
 #include <asm/pgalloc.h>
 
 #if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
+void arch_dma_prep_coherent(struct page *page, size_t size)
+{
+	cache_push(page_to_phys(page), size);
+}
+
 pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
 		unsigned long attrs)
 {
-- 
2.20.1

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Re: switch m68k to use the generic remapping DMA allocator v2

[Geert Uytterhoeven]

Hi Christoph,

On Tue, Jun 25, 2019 at 11:01 AM Christoph Hellwig <hch@lst.de> wrote:
> can you take a look at the (untested) patches below?  They convert m68k
> to use the generic remapping DMA allocator, which is also used by
> arm64 and csky.
>
> Changes since v2:
>  - fix kconfig dependencies to properly build on sun3
>  - updated a patch description to better explain why we are doing this

Thanks, both applied and queued for v5.3.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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