[U-Boot] [PATCH v3 11/18] arm: Add control over cachability of memory regions

[Simon Glass]

Add support for adjusting the cachability of an L1 section by updating
the MMU. The mmu_set_region_dcache() function allows drivers to make
these changes after the MMU is set up.

It is implemented only for ARMv7 at present.

This is needed for LCD support, where we want to make the LCD frame buffer
write-through (or off) rather than write-back.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 arch/arm/cpu/armv7/cache_v7.c |   11 +++++++
 arch/arm/include/asm/system.h |   30 ++++++++++++++++++++
 arch/arm/lib/cache-cp15.c     |   62 +++++++++++++++++++++++++++++++++-------
 3 files changed, 92 insertions(+), 11 deletions(-)

diff --git a/arch/arm/cpu/armv7/cache_v7.c b/arch/arm/cpu/armv7/cache_v7.c
index 1b4e808..5f6d039 100644
--- a/arch/arm/cpu/armv7/cache_v7.c
+++ b/arch/arm/cpu/armv7/cache_v7.c
@@ -297,6 +297,12 @@ void arm_init_before_mmu(void)
 	v7_inval_tlb();
 }
 
+void mmu_page_table_flush(unsigned long start, unsigned long stop)
+{
+	flush_dcache_range(start, stop);
+	v7_inval_tlb();
+}
+
 /*
  * Flush range from all levels of d-cache/unified-cache used:
  * Affects the range [start, start + size - 1]
@@ -329,6 +335,11 @@ void arm_init_before_mmu(void)
 void  flush_cache(unsigned long start, unsigned long size)
 {
 }
+
+void mmu_page_table_flush(unsigned long start, unsigned long stop)
+{
+}
+
 #endif /* #ifndef CONFIG_SYS_DCACHE_OFF */
 
 #ifndef CONFIG_SYS_ICACHE_OFF
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 2b28a26..f52a4fc 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -75,6 +75,36 @@ static inline void set_cr(unsigned int val)
 	isb();
 }
 
+/* options available for data cache on each page */
+enum dcache_option {
+	DCACHE_OFF,
+	DCACHE_WRITETHROUGH,
+	DCACHE_WRITEBACK,
+};
+
+/* Size of an MMU section */
+enum {
+	MMU_SECTION_SHIFT	= 20,
+	MMU_SECTION_SIZE	= 1 << MMU_SECTION_SHIFT,
+};
+
+/**
+ * Change the cache settings for a region.
+ *
+ * \param start		start address of memory region to change
+ * \param size		size of memory region to change
+ * \param option	dcache option to select
+ */
+void mmu_set_region_dcache(u32 start, int size, enum dcache_option option);
+
+/**
+ * Register an update to the page tables, and flush the TLB
+ *
+ * \param start		start address of update in page table
+ * \param stop		stop address of update in page table
+ */
+void mmu_page_table_flush(unsigned long start, unsigned long stop);
+
 #endif /* __ASSEMBLY__ */
 
 #define arch_align_stack(x) (x)
diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c
index 939de10..52a1fc6 100644
--- a/arch/arm/lib/cache-cp15.c
+++ b/arch/arm/lib/cache-cp15.c
@@ -26,12 +26,6 @@
 
 #if !(defined(CONFIG_SYS_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF))
 
-#if defined(CONFIG_SYS_ARM_CACHE_WRITETHROUGH)
-#define CACHE_SETUP	0x1a
-#else
-#define CACHE_SETUP	0x1e
-#endif
-
 DECLARE_GLOBAL_DATA_PTR;
 
 void __arm_init_before_mmu(void)
@@ -50,9 +44,52 @@ static void cp_delay (void)
 	asm volatile("" : : : "memory");
 }
 
-static inline void dram_bank_mmu_setup(int bank)
+void set_section_dcache(int section, enum dcache_option option)
 {
+	u32 value = section << MMU_SECTION_SHIFT | (3 << 10);
 	u32 *page_table = (u32 *)gd->tlb_addr;
+
+	switch (option) {
+	case DCACHE_WRITETHROUGH:
+		value |= 0x1a;
+		break;
+
+	case DCACHE_WRITEBACK:
+		value |= 0x1e;
+		break;
+
+	case DCACHE_OFF:
+		value |= 0x12;
+		break;
+	}
+
+	page_table[section] = value;
+}
+
+void __mmu_page_table_flush(unsigned long start, unsigned long stop)
+{
+	debug("%s: Warning: not implemented\n", __func__);
+}
+
+void mmu_page_table_flush(unsigned long start, unsigned long stop)
+	__attribute__((weak, alias("__mmu_page_table_flush")));
+
+void mmu_set_region_dcache(u32 start, int size, enum dcache_option option)
+{
+	u32 *page_table = (u32 *)gd->tlb_addr;
+	u32 upto, end;
+
+	end = ALIGN(start + size, MMU_SECTION_SIZE) >> MMU_SECTION_SHIFT;
+	start = start >> MMU_SECTION_SHIFT;
+	debug("mmu_set_region_dcache start=%x, size=%x, option=%d\n",
+	      start, size, option);
+	for (upto = start; upto < end; upto++)
+		set_section_dcache(upto, option);
+	mmu_page_table_flush((u32)&page_table[start], (u32)&page_table[end]);
+}
+
+static inline void dram_bank_mmu_setup(int bank)
+{
 	bd_t *bd = gd->bd;
 	int	i;
 
@@ -60,21 +97,24 @@ static inline void dram_bank_mmu_setup(int bank)
 	for (i = bd->bi_dram[bank].start >> 20;
 	     i < (bd->bi_dram[bank].start + bd->bi_dram[bank].size) >> 20;
 	     i++) {
-		page_table[i] = i << 20 | (3 << 10) | CACHE_SETUP;
+#if defined(CONFIG_SYS_ARM_CACHE_WRITETHROUGH)
+		set_section_dcache(i, DCACHE_WRITETHROUGH);
+#else
+		set_section_dcache(i, DCACHE_WRITEBACK);
+#endif
 	}
 }
 
 /* to activate the MMU we need to set up virtual memory: use 1M areas */
 static inline void mmu_setup(void)
 {
-	u32 *page_table = (u32 *)gd->tlb_addr;
 	int i;
 	u32 reg;
 
 	arm_init_before_mmu();
 	/* Set up an identity-mapping for all 4GB, rw for everyone */
 	for (i = 0; i < 4096; i++)
-		page_table[i] = i << 20 | (3 << 10) | 0x12;
+		set_section_dcache(i, DCACHE_OFF);
 
 	for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++) {
 		dram_bank_mmu_setup(i);
@@ -82,7 +122,7 @@ static inline void mmu_setup(void)
 
 	/* Copy the page table address to cp15 */
 	asm volatile("mcr p15, 0, %0, c2, c0, 0"
-		     : : "r" (page_table) : "memory");
+		     : : "r" (gd->tlb_addr) : "memory");
 	/* Set the access control to all-supervisor */
 	asm volatile("mcr p15, 0, %0, c3, c0, 0"
 		     : : "r" (~0));
-- 
1.7.7.3