powerpc/mm: rework io-workaround invocation.

ppc_md.ioremap() is only used for I/O workaround on CELL platform,
so indirect function call can be avoided.

This patch reworks the io-workaround and ioremap() functions to
use the global 'io_workaround_inited' flag for the activation
of io-workaround.

When CONFIG_PPC_IO_WORKAROUNDS or CONFIG_PPC_INDIRECT_MMIO are not
selected, the I/O workaround ioremap() voids and the global flag is
not used.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5fa3ef069fbd0f152512afaae19e7a60161454cf.1566309262.git.christophe.leroy@c-s.fr

arch/powerpc/include/asm/io-workarounds.h

@@ -8,6 +8,7 @@
 #ifndef _IO_WORKAROUNDS_H
 #define _IO_WORKAROUNDS_H
 
+#ifdef CONFIG_PPC_IO_WORKAROUNDS
 #include <linux/io.h>
 #include <asm/pci-bridge.h>
 
@@ -32,4 +33,23 @@ extern int spiderpci_iowa_init(struct iowa_bus *, void *);
 #define SPIDER_PCI_DUMMY_READ		0x0810
 #define SPIDER_PCI_DUMMY_READ_BASE	0x0814
 
+#endif
+
+#if defined(CONFIG_PPC_IO_WORKAROUNDS) && defined(CONFIG_PPC_INDIRECT_MMIO)
+extern bool io_workaround_inited;
+
+static inline bool iowa_is_active(void)
+{
+	return unlikely(io_workaround_inited);
+}
+#else
+static inline bool iowa_is_active(void)
+{
+	return false;
+}
+#endif
+
+void __iomem *iowa_ioremap(phys_addr_t addr, unsigned long size,
+			   pgprot_t prot, void *caller);
+
 #endif /* _IO_WORKAROUNDS_H */

arch/powerpc/include/asm/machdep.h

@@ -31,8 +31,6 @@ struct pci_host_bridge;
 struct machdep_calls {
 	char		*name;
 #ifdef CONFIG_PPC64
-	void __iomem *	(*ioremap)(phys_addr_t addr, unsigned long size,
-				   pgprot_t prot, void *caller);
 #ifdef CONFIG_PM
 	void		(*iommu_save)(void);
 	void		(*iommu_restore)(void);

arch/powerpc/kernel/io-workarounds.c

@@ -149,8 +149,8 @@ static const struct ppc_pci_io iowa_pci_io = {
 };
 
 #ifdef CONFIG_PPC_INDIRECT_MMIO
-static void __iomem *iowa_ioremap(phys_addr_t addr, unsigned long size,
-				  pgprot_t prot, void *caller)
+void __iomem *iowa_ioremap(phys_addr_t addr, unsigned long size,
+			   pgprot_t prot, void *caller)
 {
 	struct iowa_bus *bus;
 	void __iomem *res = __ioremap_caller(addr, size, prot, caller);
@@ -163,20 +163,17 @@ static void __iomem *iowa_ioremap(phys_addr_t addr, unsigned long size,
 	}
 	return res;
 }
-#else /* CONFIG_PPC_INDIRECT_MMIO */
-#define iowa_ioremap NULL
 #endif /* !CONFIG_PPC_INDIRECT_MMIO */
 
+bool io_workaround_inited;
+
 /* Enable IO workaround */
 static void io_workaround_init(void)
 {
-	static int io_workaround_inited;
-
 	if (io_workaround_inited)
 		return;
 	ppc_pci_io = iowa_pci_io;
-	ppc_md.ioremap = iowa_ioremap;
-	io_workaround_inited = 1;
+	io_workaround_inited = true;
 }
 
 /* Register new bus to support workaround */

arch/powerpc/mm/pgtable_64.c

@@ -35,6 +35,7 @@
 #include <asm/page.h>
 #include <asm/prom.h>
 #include <asm/io.h>
+#include <asm/io-workarounds.h>
 #include <asm/mmu_context.h>
 #include <asm/pgtable.h>
 #include <asm/mmu.h>
@@ -208,8 +209,8 @@ void __iomem * ioremap(phys_addr_t addr, unsigned long size)
 	pgprot_t prot = pgprot_noncached(PAGE_KERNEL);
 	void *caller = __builtin_return_address(0);
 
-	if (ppc_md.ioremap)
-		return ppc_md.ioremap(addr, size, prot, caller);
+	if (iowa_is_active())
+		return iowa_ioremap(addr, size, prot, caller);
 	return __ioremap_caller(addr, size, prot, caller);
 }
 
@@ -218,8 +219,8 @@ void __iomem * ioremap_wc(phys_addr_t addr, unsigned long size)
 	pgprot_t prot = pgprot_noncached_wc(PAGE_KERNEL);
 	void *caller = __builtin_return_address(0);
 
-	if (ppc_md.ioremap)
-		return ppc_md.ioremap(addr, size, prot, caller);
+	if (iowa_is_active())
+		return iowa_ioremap(addr, size, prot, caller);
 	return __ioremap_caller(addr, size, prot, caller);
 }
 
@@ -228,8 +229,8 @@ void __iomem *ioremap_coherent(phys_addr_t addr, unsigned long size)
 	pgprot_t prot = pgprot_cached(PAGE_KERNEL);
 	void *caller = __builtin_return_address(0);
 
-	if (ppc_md.ioremap)
-		return ppc_md.ioremap(addr, size, prot, caller);
+	if (iowa_is_active())
+		return iowa_ioremap(addr, size, prot, caller);
 	return __ioremap_caller(addr, size, prot, caller);
 }
 
@@ -250,8 +251,8 @@ void __iomem * ioremap_prot(phys_addr_t addr, unsigned long size,
 	 */
 	pte = pte_mkprivileged(pte);
 
-	if (ppc_md.ioremap)
-		return ppc_md.ioremap(addr, size, pte_pgprot(pte), caller);
+	if (iowa_is_active())
+		return iowa_ioremap(addr, size, pte_pgprot(pte), caller);
 	return __ioremap_caller(addr, size, pte_pgprot(pte), caller);
 }