[PATCHv3 4/9] ARM: OMAP2+: AM33XX: Reserve memory to comply with EMIF spec

[Dave Gerlach]

From: Vaibhav Bedia <vaibhav.bedia at ti.com>

SDRAM controller on AM33XX requires that a modification of certain
bit-fields in PWR_MGMT_CTRL register (ref. section 7.3.5.13 in
AM335x-Rev H) is followed by a dummy read access to SDRAM. This
scenario arises when entering a low power state like DeepSleep.
To ensure that the read is not from a cached region we reserve
some memory during bootup using the arm_memblock_steal() API.

A subsequent patch will pass along the location of the reserved
memory location to the AM335x suspend handler which modifies the
PWR_MGMT_CTRL register in the EMIF.

Signed-off-by: Vaibhav Bedia <vaibhav.bedia at ti.com>
Signed-off-by: Dave Gerlach <d-gerlach at ti.com>
---
 arch/arm/mach-omap2/board-generic.c |    2 +-
 arch/arm/mach-omap2/common.c        |   28 ++++++++++++++++++++++++++++
 arch/arm/mach-omap2/common.h        |    4 ++++
 arch/arm/mach-omap2/io.c            |    1 +
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-omap2/board-generic.c b/arch/arm/mach-omap2/board-generic.c
index be5d005..aed750c 100644
--- a/arch/arm/mach-omap2/board-generic.c
+++ b/arch/arm/mach-omap2/board-generic.c
@@ -156,7 +156,7 @@ static const char *am33xx_boards_compat[] __initdata = {
 };
 
 DT_MACHINE_START(AM33XX_DT, "Generic AM33XX (Flattened Device Tree)")
-	.reserve	= omap_reserve,
+	.reserve	= am33xx_reserve,
 	.map_io		= am33xx_map_io,
 	.init_early	= am33xx_init_early,
 	.init_irq	= omap_intc_of_init,
diff --git a/arch/arm/mach-omap2/common.c b/arch/arm/mach-omap2/common.c
index 2dabb9e..756586f 100644
--- a/arch/arm/mach-omap2/common.c
+++ b/arch/arm/mach-omap2/common.c
@@ -15,6 +15,8 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/platform_data/dsp-omap.h>
+#include <asm/memblock.h>
+#include <asm/mach/map.h>
 
 #include "common.h"
 #include "omap-secure.h"
@@ -34,3 +36,29 @@ void __init omap_reserve(void)
 	omap_secure_ram_reserve_memblock();
 	omap_barrier_reserve_memblock();
 }
+
+static phys_addr_t am33xx_paddr;
+static u32 am33xx_size;
+
+/* Steal one page physical memory for uncached read DeepSleep */
+void __init am33xx_reserve(void)
+{
+	am33xx_size = ALIGN(PAGE_SIZE, SZ_1M);
+	am33xx_paddr = arm_memblock_steal(am33xx_size, SZ_1M);
+}
+
+void __iomem *am33xx_dram_sync;
+
+void __init am33xx_dram_sync_init(void)
+{
+	struct map_desc dram_io_desc[1];
+
+	dram_io_desc[0].virtual = __phys_to_virt(am33xx_paddr);
+	dram_io_desc[0].pfn = __phys_to_pfn(am33xx_paddr);
+	dram_io_desc[0].length = am33xx_size;
+	dram_io_desc[0].type = MT_MEMORY_SO;
+
+	iotable_init(dram_io_desc, ARRAY_SIZE(dram_io_desc));
+
+	am33xx_dram_sync = (void __iomem *) dram_io_desc[0].virtual;
+}
diff --git a/arch/arm/mach-omap2/common.h b/arch/arm/mach-omap2/common.h
index dfcc182..6b8ef74 100644
--- a/arch/arm/mach-omap2/common.h
+++ b/arch/arm/mach-omap2/common.h
@@ -294,6 +294,10 @@ struct omap2_hsmmc_info;
 extern int omap4_twl6030_hsmmc_init(struct omap2_hsmmc_info *controllers);
 extern void omap_reserve(void);
 
+extern void am33xx_reserve(void);
+extern void am33xx_dram_sync_init(void);
+extern void __iomem *am33xx_dram_sync;
+
 struct omap_hwmod;
 extern int omap_dss_reset(struct omap_hwmod *);
 
diff --git a/arch/arm/mach-omap2/io.c b/arch/arm/mach-omap2/io.c
index 4a3f06f..3ad7543 100644
--- a/arch/arm/mach-omap2/io.c
+++ b/arch/arm/mach-omap2/io.c
@@ -322,6 +322,7 @@ void __init ti81xx_map_io(void)
 void __init am33xx_map_io(void)
 {
 	iotable_init(omapam33xx_io_desc, ARRAY_SIZE(omapam33xx_io_desc));
+	am33xx_dram_sync_init();
 }
 #endif
 
-- 
1.7.9.5