[PATCH v6 10/19] xen: introduce xen_alloc/free_coherent_pages
From: Stefano Stabellini <hidden>
Date: 2013-10-02 17:04:56
Also in:
lkml, xen-devel
On Tue, 1 Oct 2013, Catalin Marinas wrote:
On 30 Sep 2013, at 16:31, Konrad Rzeszutek Wilk [off-list ref] wrote:quoted
On Fri, Sep 27, 2013 at 05:09:58PM +0100, Stefano Stabellini wrote:quoted
xen_swiotlb_alloc_coherent needs to allocate a coherent buffer for cpu and devices. On native x86 and ARMv8 is sufficient to call __get_free_pages in order to get a coherent buffer, while on ARM we need to call the native dma_ops->alloc implementation. When arm64 stops using the swiotlb by default and starts having multiple dma_ops implementations, we'll use __get_dma_ops there too.I presume this is a future TODO, not some further patch (in which case you should say in here the title of it). If it is a TODO could you stick that in the sentence here somewhere to make it crytal clear that it is not implemented.Thanks for pointing this out. The arm64 patch shouldn't be different from arm here. I thought a subsequent patch already added __get_dma_ops() for arm64.
Yes, the arm64 patch already added __get_dma_ops. However I am not using __get_dma_ops to implement xen_alloc_coherent_pages for arm64 because I can just use __get_free_pages for the moment:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/include/asm/xen/page-coherent.h b/arch/arm64/include/asm/xen/page-coherent.h new file mode 100644 index 0000000..0d6ad25 --- /dev/null +++ b/arch/arm64/include/asm/xen/page-coherent.h@@ -0,0 +1,24 @@ +#ifndef _ASM_ARM64_XEN_PAGE_COHERENT_H +#define _ASM_ARM64_XEN_PAGE_COHERENT_H + +#include <asm/page.h> +#include <linux/dma-attrs.h> +#include <linux/dma-mapping.h> + +static inline void *xen_alloc_coherent_pages(struct device *hwdev, size_t size, + dma_addr_t *dma_handle, gfp_t flags, + struct dma_attrs *attrs) +{ + void *vstart = (void*)__get_free_pages(flags, get_order(size)); + *dma_handle = virt_to_phys(vstart); + return vstart; +} + +static inline void xen_free_coherent_pages(struct device *hwdev, size_t size, + void *cpu_addr, dma_addr_t dma_handle, + struct dma_attrs *attrs) +{ + free_pages((unsigned long) cpu_addr, get_order(size)); +} + +#endif /* _ASM_ARM64_XEN_PAGE_COHERENT_H */