diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/io.h | 1 | ||||
| -rw-r--r-- | arch/x86/mm/ioremap.c | 36 | ||||
| -rw-r--r-- | arch/x86/mm/pageattr.c | 3 |
3 files changed, 39 insertions, 1 deletions
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index 34a5b93704d3..4afc05ffa566 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -177,6 +177,7 @@ static inline unsigned int isa_virt_to_bus(volatile void *address) * look at pci_iomap(). */ extern void __iomem *ioremap_nocache(resource_size_t offset, unsigned long size); +extern void __iomem *ioremap_uc(resource_size_t offset, unsigned long size); extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size); extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size, unsigned long prot_val); diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c index 70e7444c6835..a493bb83aa89 100644 --- a/arch/x86/mm/ioremap.c +++ b/arch/x86/mm/ioremap.c @@ -237,7 +237,8 @@ void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size) * pat_enabled ? _PAGE_CACHE_MODE_UC : _PAGE_CACHE_MODE_UC_MINUS; * * Till we fix all X drivers to use ioremap_wc(), we will use - * UC MINUS. + * UC MINUS. Drivers that are certain they need or can already + * be converted over to strong UC can use ioremap_uc(). */ enum page_cache_mode pcm = _PAGE_CACHE_MODE_UC_MINUS; @@ -247,6 +248,39 @@ void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size) EXPORT_SYMBOL(ioremap_nocache); /** + * ioremap_uc - map bus memory into CPU space as strongly uncachable + * @phys_addr: bus address of the memory + * @size: size of the resource to map + * + * ioremap_uc performs a platform specific sequence of operations to + * make bus memory CPU accessible via the readb/readw/readl/writeb/ + * writew/writel functions and the other mmio helpers. The returned + * address is not guaranteed to be usable directly as a virtual + * address. + * + * This version of ioremap ensures that the memory is marked with a strong + * preference as completely uncachable on the CPU when possible. For non-PAT + * systems this ends up setting page-attribute flags PCD=1, PWT=1. For PAT + * systems this will set the PAT entry for the pages as strong UC. This call + * will honor existing caching rules from things like the PCI bus. Note that + * there are other caches and buffers on many busses. In particular driver + * authors should read up on PCI writes. + * + * It's useful if some control registers are in such an area and + * write combining or read caching is not desirable: + * + * Must be freed with iounmap. + */ +void __iomem *ioremap_uc(resource_size_t phys_addr, unsigned long size) +{ + enum page_cache_mode pcm = _PAGE_CACHE_MODE_UC; + + return __ioremap_caller(phys_addr, size, pcm, + __builtin_return_address(0)); +} +EXPORT_SYMBOL_GPL(ioremap_uc); + +/** * ioremap_wc - map memory into CPU space write combined * @phys_addr: bus address of the memory * @size: size of the resource to map diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 5ddd9005f6c3..c77abd7f92a2 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -1467,6 +1467,9 @@ int _set_memory_uc(unsigned long addr, int numpages) { /* * for now UC MINUS. see comments in ioremap_nocache() + * If you really need strong UC use ioremap_uc(), but note + * that you cannot override IO areas with set_memory_*() as + * these helpers cannot work with IO memory. */ return change_page_attr_set(&addr, numpages, cachemode2pgprot(_PAGE_CACHE_MODE_UC_MINUS), |