[PATCH 16/26] asm-generic: don't provide ioremap for CONFIG_MMU

Christoph Hellwig
2019-08-17T07:32:43Z

All MMU-enabled ports have a non-trivial ioremap and should thus provide
the prototype for their implementation instead of providing a generic
one unless a different symbol is not defined. Note that this only
affects sparc32 nds32 as all others do provide their own version.

Also update the kerneldoc comments in asm-generic/io.h to explain the
situation around the default ioremap* implementations correctly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/nds32/include/asm/io.h | 2 ++
arch/sparc/include/asm/io_32.h | 1 +
include/asm-generic/io.h | 29 ++++++++---------------------
3 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/arch/nds32/include/asm/io.h b/arch/nds32/include/asm/io.h
index 16f262322b8f..fb0e8a24c7af 100644
--- a/arch/nds32/include/asm/io.h
+++ b/arch/nds32/include/asm/io.h
@@ -6,6 +6,7 @@

#include <linux/types.h>

+void __iomem *ioremap(phys_addr_t phys_addr, size_t size);
extern void iounmap(volatile void __iomem *addr);
#define __raw_writeb __raw_writeb
static inline void __raw_writeb(u8 val, volatile void __iomem *addr)
@@ -80,4 +81,5 @@ static inline u32 __raw_readl(const volatile void __iomem *addr)
#define writew(v,c) ({ __iowmb(); writew_relaxed((v),(c)); })
#define writel(v,c) ({ __iowmb(); writel_relaxed((v),(c)); })
#include <asm-generic/io.h>
+
#endif /* __ASM_NDS32_IO_H */
diff --git a/arch/sparc/include/asm/io_32.h b/arch/sparc/include/asm/io_32.h
index df2dc1784673..9a52d9506f80 100644
--- a/arch/sparc/include/asm/io_32.h
+++ b/arch/sparc/include/asm/io_32.h
@@ -127,6 +127,7 @@ static inline void sbus_memcpy_toio(volatile void __iomem *dst,
* Bus number may be embedded in the higher bits of the physical address.
* This is why we have no bus number argument to ioremap().
*/
+void __iomem *ioremap(phys_addr_t offset, size_t size);
void iounmap(volatile void __iomem *addr);
/* Create a virtual mapping cookie for an IO port range */
void __iomem *ioport_map(unsigned long port, unsigned int nr);
diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index a98ed6325727..6a5edc23afe2 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -922,28 +922,16 @@ static inline void *phys_to_virt(unsigned long address)
/**
* DOC: ioremap() and ioremap_*() variants
*
- * If you have an IOMMU your architecture is expected to have both ioremap()
- * and iounmap() implemented otherwise the asm-generic helpers will provide a
- * direct mapping.
+ * Architectures with an MMU are expected to provide ioremap() and iounmap()
+ * themselves. For NOMMU architectures we provide a default nop-op
+ * implementation that expect that the physical address used for MMIO are
+ * already marked as uncached, and can be used as kernel virtual addresses.
*
- * There are ioremap_*() call variants, if you have no IOMMU we naturally will
- * default to direct mapping for all of them, you can override these defaults.
- * If you have an IOMMU you are highly encouraged to provide your own
- * ioremap variant implementation as there currently is no safe architecture
- * agnostic default. To avoid possible improper behaviour default asm-generic
- * ioremap_*() variants all return NULL when an IOMMU is available. If you've
- * defined your own ioremap_*() variant you must then declare your own
- * ioremap_*() variant as defined to itself to avoid the default NULL return.
+ * ioremap_wc() and ioremap_wt() can provide more relaxed caching attributes
+ * for specific drivers if the architecture choses to implement them. If they
+ * are not implemented we fall back to plain ioremap.
*/
#ifndef CONFIG_MMU
-
-/*
- * Change "struct page" to physical address.
- *
- * This implementation is for the no-MMU case only... if you have an MMU
- * you'll need to provide your own definitions.
- */
-
#ifndef ioremap
#define ioremap ioremap
static inline void __iomem *ioremap(phys_addr_t offset, size_t size)
@@ -954,14 +942,13 @@ static inline void __iomem *ioremap(phys_addr_t offset, size_t size)

#ifndef iounmap
#define iounmap iounmap
-
static inline void iounmap(void __iomem *addr)
{
}
#endif
#endif /* CONFIG_MMU */
+
#ifndef ioremap_nocache
-void __iomem *ioremap(phys_addr_t phys_addr, size_t size);
#define ioremap_nocache ioremap_nocache
static inline void __iomem *ioremap_nocache(phys_addr_t offset, size_t size)
{
--
2.20.1