| | 34 | |
| | 35 | Edit: |
| | 36 | |
| | 37 | ioremap_cache() is uncached by default since a long time. |
| | 38 | |
| | 39 | all 5.X kernels down to version 5.0 |
| | 40 | all 4.X kernels down to version 4.0 |
| | 41 | all 3.X kernels down to version 3.0 |
| | 42 | |
| | 43 | from version 2.6.25 onwards we know for sure |
| | 44 | that ioremap_cache() has uncached semantics by default. |
| | 45 | |
| | 46 | [https://elixir.bootlin.com/linux/v2.6.25/source/include/asm-x86/io_64.h#L161][[BR]] |
| | 47 | |
| | 48 | {{{ |
| | 49 | * This one maps high address device memory and turns off caching for that area. |
| | 50 | * it's useful if some control registers are in such an area and write combining |
| | 51 | * or read caching is not desirable: |
| | 52 | */ |
| | 53 | extern void __iomem *ioremap_nocache(resource_size_t offset, unsigned long size); |
| | 54 | extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size); |
| | 55 | |
| | 56 | /* |
| | 57 | * The default ioremap() behavior is non-cached: |
| | 58 | */ |
| | 59 | static inline void __iomem *ioremap(resource_size_t offset, unsigned long size) |
| | 60 | { |
| | 61 | return ioremap_nocache(offset, size); |
| | 62 | } |
| | 63 | }}} |
| | 64 | |
| | 65 | That means we can and should replace ioremap_nocache() usage |
| | 66 | with ioremap_cache() and make kernel version 2.6.25 the tipping |
| | 67 | point for this. |
