[ARM] 3439/2: xsc3: add I/O coherency support

Patch from Lennert Buytenhek

This patch adds support for the I/O coherent cache available on the
xsc3.  The approach is to provide a simple API to determine whether the
chipset supports coherency by calling arch_is_coherent() and then
setting the appropriate system memory PTE and PMD bits.  In addition,
we call this API on dma_alloc_coherent() and dma_map_single() calls.
A generic version exists that will compile out all the coherency-related
code that is not needed on the majority of ARM systems.

Note that we do not check for coherency in the dma_alloc_writecombine()
function as that still requires a special PTE setting.  We also don't
touch dma_mmap_coherent() as that is a special ARM-only API that is by
definition only used on non-coherent system.
Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/setup.c

@@ -252,6 +252,9 @@ static void __init dump_cpu_info(int cpu)
 			dump_cache("cache", cpu, CACHE_ISIZE(info));
 		}
 	}
+
+	if (arch_is_coherent())
+		printk("Cache coherency enabled\n");
 }
 
 int cpu_architecture(void)

arch/arm/mach-ixp23xx/pci.c

@@ -219,6 +219,12 @@ static void __init ixp23xx_pci_common_init(void)
 		*IXP23XX_PCI_CPP_ADDR_BITS &= ~(1 << 1);
 	} else {
 		*IXP23XX_PCI_CPP_ADDR_BITS |= (1 << 1);
+
+		/*
+		 * Enable coherency on A2 silicon.
+		 */
+		if (arch_is_coherent())
+			*IXP23XX_CPP2XSI_CURR_XFER_REG3 &= ~IXP23XX_CPP2XSI_COH_OFF;
 	}
 }
 

arch/arm/mm/consistent.c

@@ -18,6 +18,7 @@
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 
+#include <asm/memory.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/sizes.h>
@@ -272,6 +273,17 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
 void *
 dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp)
 {
+	if (arch_is_coherent()) {
+		void *virt;
+
+		virt = kmalloc(size, gfp);
+		if (!virt)
+			return NULL;
+		*handle =  virt_to_dma(dev, virt);
+
+		return virt;
+	}
+
 	return __dma_alloc(dev, size, handle, gfp,
 			   pgprot_noncached(pgprot_kernel));
 }
@@ -350,6 +362,11 @@ void dma_free_coherent(struct device *dev, size_t size, void *cpu_addr, dma_addr
 
 	WARN_ON(irqs_disabled());
 
+	if (arch_is_coherent()) {
+		kfree(cpu_addr);
+		return;
+	}
+
 	size = PAGE_ALIGN(size);
 
 	spin_lock_irqsave(&consistent_lock, flags);

arch/arm/mm/mm-armv.c

@@ -388,6 +388,17 @@ void __init build_mem_type_table(void)
 	cp = &cache_policies[cachepolicy];
 	kern_pgprot = user_pgprot = cp->pte;
 
+	/*
+	 * Enable CPU-specific coherency if supported.
+	 * (Only available on XSC3 at the moment.)
+	 */
+	if (arch_is_coherent()) {
+		if (cpu_is_xsc3()) {
+			mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
+			mem_types[MT_MEMORY].prot_pte |= L_PTE_COHERENT;
+		}
+	}
+
 	/*
 	 * ARMv6 and above have extended page tables.
 	 */

arch/arm/mm/proc-xsc3.S

@@ -371,7 +371,7 @@ ENTRY(cpu_xsc3_switch_mm)
 ENTRY(cpu_xsc3_set_pte)
 	str	r1, [r0], #-2048		@ linux version
 
-	bic	r2, r1, #0xff0
+	bic	r2, r1, #0xdf0			@ Keep C, B, coherency bits
 	orr	r2, r2, #PTE_TYPE_EXT		@ extended page
 
 	eor	r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY

include/asm-arm/arch-ixp23xx/memory.h

@@ -28,6 +28,7 @@
  *		to an address that the kernel can use.
  */
 #ifndef __ASSEMBLY__
+#include <asm/mach-types.h>
 
 #define __virt_to_bus(v)						\
 	({ unsigned int ret;						\
@@ -40,6 +41,22 @@
 	data = *((volatile int *)IXP23XX_PCI_SDRAM_BAR);		\
 	 __phys_to_virt((((b - (data & 0xfffffff0)) + 0x00000000))); })
 
+/*
+ * Coherency support.  Only supported on A2 CPUs or on A1
+ * systems that have the cache coherency workaround.
+ */
+static inline int __ixp23xx_arch_is_coherent(void)
+{
+	extern unsigned int processor_id;
+
+	if (((processor_id & 15) >= 2) || machine_is_roadrunner())
+		return 1;
+
+	return 0;
+}
+
+#define arch_is_coherent()	__ixp23xx_arch_is_coherent()
+
 #endif
 
 

include/asm-arm/dma-mapping.h

@@ -47,7 +47,7 @@ static inline int dma_get_cache_alignment(void)
 
 static inline int dma_is_consistent(dma_addr_t handle)
 {
-	return 0;
+	return !!arch_is_coherent();
 }
 
 /*
@@ -145,7 +145,9 @@ static inline dma_addr_t
 dma_map_single(struct device *dev, void *cpu_addr, size_t size,
 	       enum dma_data_direction dir)
 {
-	consistent_sync(cpu_addr, size, dir);
+	if (!arch_is_coherent())
+		consistent_sync(cpu_addr, size, dir);
+
 	return virt_to_dma(dev, (unsigned long)cpu_addr);
 }
 #else
@@ -255,7 +257,9 @@ dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 
 		sg->dma_address = page_to_dma(dev, sg->page) + sg->offset;
 		virt = page_address(sg->page) + sg->offset;
-		consistent_sync(virt, sg->length, dir);
+
+		if (!arch_is_coherent())
+			consistent_sync(virt, sg->length, dir);
 	}
 
 	return nents;
@@ -310,14 +314,16 @@ static inline void
 dma_sync_single_for_cpu(struct device *dev, dma_addr_t handle, size_t size,
 			enum dma_data_direction dir)
 {
-	consistent_sync((void *)dma_to_virt(dev, handle), size, dir);
+	if (!arch_is_coherent())
+		consistent_sync((void *)dma_to_virt(dev, handle), size, dir);
 }
 
 static inline void
 dma_sync_single_for_device(struct device *dev, dma_addr_t handle, size_t size,
 			   enum dma_data_direction dir)
 {
-	consistent_sync((void *)dma_to_virt(dev, handle), size, dir);
+	if (!arch_is_coherent())
+		consistent_sync((void *)dma_to_virt(dev, handle), size, dir);
 }
 #else
 extern void dma_sync_single_for_cpu(struct device*, dma_addr_t, size_t, enum dma_data_direction);
@@ -347,7 +353,8 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
 
 	for (i = 0; i < nents; i++, sg++) {
 		char *virt = page_address(sg->page) + sg->offset;
-		consistent_sync(virt, sg->length, dir);
+		if (!arch_is_coherent())
+			consistent_sync(virt, sg->length, dir);
 	}
 }
 
@@ -359,7 +366,8 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
 
 	for (i = 0; i < nents; i++, sg++) {
 		char *virt = page_address(sg->page) + sg->offset;
-		consistent_sync(virt, sg->length, dir);
+		if (!arch_is_coherent())
+			consistent_sync(virt, sg->length, dir);
 	}
 }
 #else

include/asm-arm/memory.h

@@ -234,6 +234,14 @@ static inline __deprecated void *bus_to_virt(unsigned long x)
 #define virt_to_dma(dev, addr)		(__arch_virt_to_dma(dev, addr))
 #endif
 
+/*
+ * Optional coherency support.  Currently used only by selected
+ * Intel XSC3-based systems.
+ */
+#ifndef arch_is_coherent
+#define arch_is_coherent()		0
+#endif
+
 #endif
 
 #include <asm-generic/memory_model.h>

include/asm-arm/pgtable-hwdef.h

@@ -73,6 +73,7 @@
 #define PTE_EXT_AP_URW_SRW	(PTE_EXT_AP1|PTE_EXT_AP0)
 #define PTE_EXT_TEX(x)		((x) << 6)	/* v5 */
 #define PTE_EXT_APX		(1 << 9)	/* v6 */
+#define PTE_EXT_COHERENT	(1 << 9)	/* XScale3 */
 #define PTE_EXT_SHARED		(1 << 10)	/* v6 */
 #define PTE_EXT_NG		(1 << 11)	/* v6 */
 

include/asm-arm/pgtable.h

@@ -156,6 +156,7 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
 #define L_PTE_WRITE		(1 << 5)
 #define L_PTE_EXEC		(1 << 6)
 #define L_PTE_DIRTY		(1 << 7)
+#define L_PTE_COHERENT		(1 << 9)	/* I/O coherent (xsc3) */
 #define L_PTE_SHARED		(1 << 10)	/* shared between CPUs (v6) */
 #define L_PTE_ASID		(1 << 11)	/* non-global (use ASID, v6) */