sh: P4 ioremap pass-through

This patch adds a pass-through case when ioremapping P4 addresses.

Addresses passed to ioremap() should be physical addresses, so the
best option is usually to convert the virtual address to a physical
address before calling ioremap. This will give you a virtual address
in P2 which matches the physical address and this works well for
most internal hardware blocks on the SuperH architecture.

However, some hardware blocks must be accessed through P4. Converting
the P4 address to a physical and then back to a P2 does not work. One
example of this is the sh7722 TMU block, it must be accessed through P4.

Without this patch P4 addresses will be mapped using PTEs which
requires the page allocator to be up and running.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 15 insertions, 0 deletions

diff --git a/arch/sh/include/asm/addrspace.h b/arch/sh/include/asm/addrspace.h
index 2702d81bfc0..36736c7e93d 100644
--- a/arch/sh/include/asm/addrspace.h
+++ b/arch/sh/include/asm/addrspace.h
@@ -49,5 +49,16 @@
 /* Check if an address can be reached in 29 bits */
 #define IS_29BIT(a)	(((unsigned long)(a)) < 0x20000000)
 
+#ifdef CONFIG_SH_STORE_QUEUES
+/*
+ * This is a special case for the SH-4 store queues, as pages for this
+ * space still need to be faulted in before it's possible to flush the
+ * store queue cache for writeout to the remapped region.
+ */
+#define P3_ADDR_MAX		(P4SEG_STORE_QUE + 0x04000000)
+#else
+#define P3_ADDR_MAX		P4SEG
+#endif
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_SH_ADDRSPACE_H */
diff --git a/arch/sh/include/asm/io.h b/arch/sh/include/asm/io.h
index 65eaae34e75..61f6dae4053 100644
--- a/arch/sh/include/asm/io.h
+++ b/arch/sh/include/asm/io.h
@@ -260,6 +260,10 @@ __ioremap_mode(unsigned long offset, unsigned long size, unsigned long flags)
 
 		return (void __iomem *)P2SEGADDR(offset);
 	}
+
+	/* P4 above the store queues are always mapped. */
+	if (unlikely(offset >= P3_ADDR_MAX))
+		return (void __iomem *)P4SEGADDR(offset);
 #endif
 
 	return __ioremap(offset, size, flags);