AT91: Fix AT91SAM9G20 reset as per the errata in the data sheet

If the SDRAM is not cleanly shutdown before reset it can be left driving
the bus, which then stops the bootloader booting from NAND.

Signed-off-by: Peter Horton <phorton@bitbox.co.uk>
[nicolas.ferre@atmel.com: change file header line order]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

3 files changed, 63 insertions, 2 deletions

diff --git a/arch/arm/mach-at91/Makefile b/arch/arm/mach-at91/Makefile
index 72b6b1b1722a..6e97edd47c5f 100644
--- a/arch/arm/mach-at91/Makefile
+++ b/arch/arm/mach-at91/Makefile
@@ -16,7 +16,7 @@ obj-$(CONFIG_ARCH_AT91SAM9261)	+= at91sam9261.o at91sam926x_time.o at91sam9261_d
 obj-$(CONFIG_ARCH_AT91SAM9G10)  += at91sam9261.o at91sam926x_time.o at91sam9261_devices.o sam9_smc.o
 obj-$(CONFIG_ARCH_AT91SAM9263)  += at91sam9263.o at91sam926x_time.o at91sam9263_devices.o sam9_smc.o
 obj-$(CONFIG_ARCH_AT91SAM9RL)   += at91sam9rl.o at91sam926x_time.o at91sam9rl_devices.o sam9_smc.o
-obj-$(CONFIG_ARCH_AT91SAM9G20)  += at91sam9260.o at91sam926x_time.o at91sam9260_devices.o sam9_smc.o
+obj-$(CONFIG_ARCH_AT91SAM9G20)  += at91sam9260.o at91sam926x_time.o at91sam9260_devices.o sam9_smc.o at91sam9g20_reset.o
 obj-$(CONFIG_ARCH_AT91SAM9G45)  += at91sam9g45.o at91sam926x_time.o at91sam9g45_devices.o sam9_smc.o
 obj-$(CONFIG_ARCH_AT91CAP9)     += at91cap9.o at91sam926x_time.o at91cap9_devices.o sam9_smc.o
 obj-$(CONFIG_ARCH_AT572D940HF)  += at572d940hf.o at91sam926x_time.o at572d940hf_devices.o sam9_smc.o
diff --git a/arch/arm/mach-at91/at91sam9260.c b/arch/arm/mach-at91/at91sam9260.c
index 0894f1077be7..f8844506eabb 100644
--- a/arch/arm/mach-at91/at91sam9260.c
+++ b/arch/arm/mach-at91/at91sam9260.c
@@ -25,6 +25,8 @@
 #include "generic.h"
 #include "clock.h"
 
+extern void at91sam9g20_reset(void);
+
 static struct map_desc at91sam9260_io_desc[] __initdata = {
         {
                 .virtual        = AT91_VA_BASE_SYS,
@@ -327,7 +329,11 @@ void __init at91sam9260_initialize(unsigned long main_clock)
         else
                 iotable_init(at91sam9260_sram_desc, ARRAY_SIZE(at91sam9260_sram_desc));
 
-        at91_arch_reset = at91sam9260_reset;
+        if (cpu_is_at91sam9g20())
+                at91_arch_reset = at91sam9g20_reset;
+        else
+                at91_arch_reset = at91sam9260_reset;
+
         pm_power_off = at91sam9260_poweroff;
         at91_extern_irq = (1 << AT91SAM9260_ID_IRQ0) | (1 << AT91SAM9260_ID_IRQ1)
                         | (1 << AT91SAM9260_ID_IRQ2);
diff --git a/arch/arm/mach-at91/at91sam9g20_reset.S b/arch/arm/mach-at91/at91sam9g20_reset.S
new file mode 100644
index 000000000000..f6e9b037f73c
--- /dev/null
+++ b/arch/arm/mach-at91/at91sam9g20_reset.S
@@ -0,0 +1,55 @@
+/*
+ * reset AT91SAM9G20 as per errata
+ *
+ * (C) BitBox Ltd 2010
+ *
+ * unless the SDRAM is cleanly shutdown before we hit the
+ * reset register it can be left driving the data bus and
+ * killing the chance of a subsequent boot from NAND
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#define CP15_CR_I                       (1 << 12)
+
+#define SYS_VIRT_OFS                    (-0x01000000)
+
+#define SDRAMC_BASE                     (SYS_VIRT_OFS + 0xffffea00)
+#define  SDRAMC_TR                      0x0004
+#define  SDRAMC_LPR                     0x0010
+#define   SDRAMC_LPCB_POWER_DOWN        2
+
+#define RSTC_BASE                       (SYS_VIRT_OFS + 0xfffffd00)
+#define  RSTC_CR                        0x0000
+#define   RSTC_PROCRST                  (1 << 0)
+#define   RSTC_PERRST                   (1 << 2)
+#define   RSTC_KEY                      (0xa5 << 24)
+
+                        .arm
+
+                        .globl  at91sam9g20_reset
+
+at91sam9g20_reset:      mov     r0, #0
+                        mcr     p15, 0, r0, c7, c5, 0   @ flush I-cache
+
+                        mrc     p15, 0, r0, c1, c0, 0
+                        orr     r0, r0, #CP15_CR_I
+                        mcr     p15, 0, r0, c1, c0, 0   @ enable I-cache
+
+                        ldr     r0, =SDRAMC_BASE        @ preload constants
+                        ldr     r1, =RSTC_BASE
+
+                        mov     r2, #1
+                        mov     r3, #SDRAMC_LPCB_POWER_DOWN
+                        ldr     r4, =RSTC_KEY | RSTC_PERRST | RSTC_PROCRST
+
+                        .balign 32                      @ align to cache line
+
+                        str     r2, [r0, #SDRAMC_TR]    @ disable SDRAM access
+                        str     r3, [r0, #SDRAMC_LPR]   @ power down SDRAM
+                        str     r4, [r1, #RSTC_CR]      @ reset processor
+
+                        b       .