[PATCHv3 2/2] arm64: Enable CMA

[Will Deacon]

Hi Laura,

Couple of really minor comments...

On Tue, Dec 10, 2013 at 09:43:36PM +0000, Laura Abbott wrote:
> arm64 bit targets need the features CMA provides. Add the appropriate
> hooks, header files, and Kconfig to allow this to happen.
> 
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Marek Szyprowski <m.szyprowski at samsung.com>
> Signed-off-by: Laura Abbott <lauraa at codeaurora.org>
> ---
>  arch/arm64/Kconfig                      |    1 +
>  arch/arm64/include/asm/dma-contiguous.h |   29 +++++++++++++++++++++++++++++
>  arch/arm64/mm/dma-mapping.c             |   25 +++++++++++++++++++++++--
>  arch/arm64/mm/init.c                    |    3 +++
>  4 files changed, 56 insertions(+), 2 deletions(-)
>  create mode 100644 arch/arm64/include/asm/dma-contiguous.h
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 9737e97..26e4bef 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -22,6 +22,7 @@ config ARM64
>  	select HAVE_DEBUG_KMEMLEAK
>  	select HAVE_DMA_API_DEBUG
>  	select HAVE_DMA_ATTRS
> +	select HAVE_DMA_CONTIGUOUS
>  	select HAVE_GENERIC_DMA_COHERENT
>  	select HAVE_GENERIC_HARDIRQS
>  	select HAVE_HW_BREAKPOINT if PERF_EVENTS
> diff --git a/arch/arm64/include/asm/dma-contiguous.h b/arch/arm64/include/asm/dma-contiguous.h
> new file mode 100644
> index 0000000..bc32516
> --- /dev/null
> +++ b/arch/arm64/include/asm/dma-contiguous.h
> @@ -0,0 +1,29 @@
> +/*
> + * Copyright (c) 2013, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef ASMARM64_DMA_CONTIGUOUS_H
> +#define ASMARM64_DMA_CONTIGUOUS_H

We've tried to keep these guards consistent for the arm64 headers, so this
would be: __ASM_DMA_CONTIGUOUS_H.

> +
> +#ifdef __KERNEL__
> +#ifdef CONFIG_CMA

Why is this not CONFIG_DMA_CMA?

> +#include <linux/types.h>
> +#include <asm-generic/dma-contiguous.h>
> +
> +static inline void
> +dma_contiguous_early_fixup(phys_addr_t base, unsigned long size) { }
> +
> +#endif
> +#endif
> +
> +#endif
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index 4134212..29d10b9 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -21,6 +21,7 @@
>  #include <linux/export.h>
>  #include <linux/slab.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/dma-contiguous.h>
>  #include <linux/vmalloc.h>
>  #include <linux/swiotlb.h>
>  
> @@ -36,14 +37,34 @@ static void *arm64_swiotlb_alloc_coherent(struct device *dev, size_t size,
>  	if (dev && IS_ENABLED(CONFIG_ZONE_DMA32) &&
>  	    dev->coherent_dma_mask <= DMA_BIT_MASK(32))
>  		flags |= GFP_DMA32;
> -	return swiotlb_alloc_coherent(dev, size, dma_handle, flags);
> +	if (IS_ENABLED(CONFIG_DMA_CMA)) {
> +		struct page *page;
> +
> +		page = dma_alloc_from_contiguous(dev, size >> PAGE_SHIFT,
> +							get_order(size));
> +		if (!page)
> +			return NULL;

Seems a shame to fail the allocation if CMA can't manage it. Is there a good
reason not to fall back to swiotlb (other than complicating the freeing
paths)?

Will