memremap: add arch specific hook for MEMREMAP_WB mappings (c269cba3) · Commits · e / devices / android_kernel_teracube_emerald

Currently, the memremap code serves MEMREMAP_WB mappings directly from the kernel direct mapping, unless the region is in high memory, in which case it falls back to using ioremap_cache(). However, the semantics of ioremap_cache() are not unambiguously defined, and on ARM, it will actually result in a mapping type that differs from the attributes used for the linear mapping, and for this reason, the ioremap_cache() call fails if the region is part of the memory managed by the kernel. So instead, implement an optional hook 'arch_memremap_wb' whose default implementation calls ioremap_cache() as before, but which can be overridden by the architecture to do what is appropriate for it. Acked-by:

Dan Williams <dan.j.williams@intel.com> Signed-off-by:

Ard Biesheuvel <ard.biesheuvel@linaro.org>

kernel/memremap.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -27,6 +27,13 @@ __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
		}
		#endif

		#ifndef arch_memremap_wb
		static void *arch_memremap_wb(resource_size_t offset, unsigned long size)
		{
		return (__force void *)ioremap_cache(offset, size);
		}
		#endif

		static void *try_ram_remap(resource_size_t offset, size_t size)
		{
		unsigned long pfn = PHYS_PFN(offset);
		@@ -34,7 +41,7 @@ static void *try_ram_remap(resource_size_t offset, size_t size)
		/* In the simple case just return the existing linear address */
		if (pfn_valid(pfn) && !PageHighMem(pfn_to_page(pfn)))
		return __va(offset);
		return NULL; /* fallback to ioremap_cache */
		return NULL; /* fallback to arch_memremap_wb */
		}

		/**
		@@ -90,7 +97,7 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
		if (is_ram == REGION_INTERSECTS)
		addr = try_ram_remap(offset, size);
		if (!addr)
		addr = ioremap_cache(offset, size);
		addr = arch_memremap_wb(offset, size);
		}

		/*