[PATCH][v2] powerpc/mm: using two zones for freescale 64 bit kernel

[Kumar Gala]

On Aug 24, 2012, at 5:50 AM, Shaohui Xie wrote:

> PowerPC platform only supports ZONE_DMA zone for 64bit kernel, so all the
> memory will be put into this zone. If the memory size is greater than
> the device's DMA capability and device uses dma_alloc_coherent to allocate
> memory, it will get an address which is over the device's DMA addressing,
> the device will fail.
> 
> So we split the memory to two zones: zone ZONE_DMA32 & ZONE_NORMAL, since
> we already allocate PCICSRBAR/PEXCSRBAR right below the 4G boundary (if the
> lowest PCI address is above 4G), so we constrain the DMA zone ZONE_DMA32
> to 2GB, also, we clear flag __GFP_DMA & __GFP_DMA32 and set __GFP_DMA32 only
> if the device's dma_mask < total memory size. By doing this, devices which
> cannot DMA all the memory will be limited to ZONE_DMA32, but devices which
> can DMA all the memory will not be affected by this limitation.
> 
> Signed-off-by: Shaohui Xie <Shaohui.Xie at freescale.com>
> Signed-off-by: Mingkai Hu <Mingkai.hu at freescale.com>
> Signed-off-by: Chen Yuanquan <B41889 at freescale.com>
> ---
> changes for v2:
> 1. use a config option for using two zones (ZONE_DMA32 & ZONE_NORMAL) in
> freescale 64 bit kernel.
> 
> arch/powerpc/Kconfig      |    3 +++
> arch/powerpc/kernel/dma.c |   15 +++++++++++++++
> arch/powerpc/mm/mem.c     |    4 ++++
> 3 files changed, 22 insertions(+), 0 deletions(-)

Ben,

What's the feeling of doing this on ppc64 always? 

- k

> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 352f416..a96fbbb 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -629,6 +629,9 @@ config ZONE_DMA
> 	bool
> 	default y
> 
> +config ZONE_DMA32
> +	def_bool (PPC64 && PPC_FSL_BOOK3E)
> +
> config NEED_DMA_MAP_STATE
> 	def_bool (PPC64 || NOT_COHERENT_CACHE)
> 
> diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
> index 355b9d8..cbf5ac1 100644
> --- a/arch/powerpc/kernel/dma.c
> +++ b/arch/powerpc/kernel/dma.c
> @@ -41,9 +41,24 @@ void *dma_direct_alloc_coherent(struct device *dev, size_t size,
> #else
> 	struct page *page;
> 	int node = dev_to_node(dev);
> +#ifdef CONFIG_ZONE_DMA32
> +	phys_addr_t top_ram_pfn = memblock_end_of_DRAM();
> 
> +	/*
> +	 * check for crappy device which has dma_mask < ZONE_DMA, and
> +	 * we are not going to support it, just warn and fail.
> +	 */
> +	if (*dev->dma_mask < DMA_BIT_MASK(31)) {
> +		dev_err(dev, "Unsupported dma_mask 0x%llx\n", *dev->dma_mask);
> +		return NULL;
> +	}
> 	/* ignore region specifiers */
> +	flag  &= ~(__GFP_HIGHMEM | __GFP_DMA | __GFP_DMA32);
> +	if (*dev->dma_mask < top_ram_pfn - 1)
> +		flag |= __GFP_DMA32;
> +#else
> 	flag  &= ~(__GFP_HIGHMEM);
> +#endif
> 
> 	page = alloc_pages_node(node, flag, get_order(size));
> 	if (page == NULL)
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index baaafde..2a11e49 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -280,6 +280,10 @@ void __init paging_init(void)
> #ifdef CONFIG_HIGHMEM
> 	max_zone_pfns[ZONE_DMA] = lowmem_end_addr >> PAGE_SHIFT;
> 	max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
> +#elif defined CONFIG_ZONE_DMA32
> +	max_zone_pfns[ZONE_DMA32] = min_t(phys_addr_t, top_of_ram,
> +					1ull << 31) >> PAGE_SHIFT;
> +	max_zone_pfns[ZONE_NORMAL] = top_of_ram >> PAGE_SHIFT;
> #else
> 	max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
> #endif
> -- 
> 1.6.4
> 
> 
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