[ARM] 5264/2: [AT91] Suspend-to-RAM disables main oscillator

This patch adds support for a low(er)-power suspend-to-RAM.
In addition to the SDRAM being put into self-refresh mode, the Master
Clock is set to the Slow-clock rate (32Khz) and PLLA & PLLB are
disabled.
Certain peripherals are therefore also disabled, and thus cannot be
used as wakeup sources.

This patch has been included in the AT91 patches in various forms
since 2.6.19 and a number of people have worked or commented on it,
most notably:
 Savin Zlobec (for the original AT91RM9200 support)
 Anti Sullin (for the SAM9260 version)
 David Brownell, etc.

Signed-off-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 297 insertions, 0 deletions

diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
index 68537e37387f..5aafb2e2ca7a 100644
--- a/arch/arm/mach-at91/Kconfig
+++ b/arch/arm/mach-at91/Kconfig
@@ -323,6 +323,19 @@ config AT91_PROGRAMMABLE_CLOCKS
           Select this if you need to program one or more of the PCK0..PCK3
           programmable clock outputs.
 
+config AT91_SLOW_CLOCK
+        bool "Suspend-to-RAM disables main oscillator"
+        depends on SUSPEND
+        help
+          Select this if you want Suspend-to-RAM to save the most power
+          possible (without powering off the CPU) by disabling the PLLs
+          and main oscillator so that only the 32 KiHz clock is available.
+
+          When only that slow-clock is available, some peripherals lose
+          functionality.  Many can't issue wakeup events unless faster
+          clocks are available.  Some lose their operating state and
+          need to be completely re-initialized.
+
 config AT91_TIMER_HZ
        int "Kernel HZ (jiffies per second)"
        range 32 1024
diff --git a/arch/arm/mach-at91/Makefile b/arch/arm/mach-at91/Makefile
index a95c49bdf927..cca612d97ca2 100644
--- a/arch/arm/mach-at91/Makefile
+++ b/arch/arm/mach-at91/Makefile
@@ -65,6 +65,7 @@ obj-y				+= leds.o
 
 # Power Management
 obj-$(CONFIG_PM)                += pm.o
+obj-$(CONFIG_AT91_SLOW_CLOCK)   += pm_slowclock.o
 
 ifeq ($(CONFIG_PM_DEBUG),y)
 CFLAGS_pm.o += -DDEBUG
diff --git a/arch/arm/mach-at91/pm_slowclock.S b/arch/arm/mach-at91/pm_slowclock.S
new file mode 100644
index 000000000000..987fab3d846a
--- /dev/null
+++ b/arch/arm/mach-at91/pm_slowclock.S
@@ -0,0 +1,283 @@
+/*
+ * arch/arm/mach-at91/pm_slow_clock.S
+ *
+ *  Copyright (C) 2006 Savin Zlobec
+ *
+ * AT91SAM9 support:
+ *  Copyright (C) 2007 Anti Sullin <anti.sullin@artecdesign.ee
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/linkage.h>
+#include <mach/hardware.h>
+#include <mach/at91_pmc.h>
+
+#ifdef CONFIG_ARCH_AT91RM9200
+#include <mach/at91rm9200_mc.h>
+#elif defined(CONFIG_ARCH_AT91CAP9)
+#include <mach/at91cap9_ddrsdr.h>
+#else
+#include <mach/at91sam9_sdramc.h>
+#endif
+
+
+#ifdef CONFIG_ARCH_AT91SAM9263
+/*
+ * FIXME either or both the SDRAM controllers (EB0, EB1) might be in use;
+ * handle those cases both here and in the Suspend-To-RAM support.
+ */
+#define AT91_SDRAMC     AT91_SDRAMC0
+#warning Assuming EB1 SDRAM controller is *NOT* used
+#endif
+
+/*
+ * When SLOWDOWN_MASTER_CLOCK is defined we will also slow down the Master
+ * clock during suspend by adjusting its prescalar and divisor.
+ * NOTE: This hasn't been shown to be stable on SAM9s; and on the RM9200 there
+ *       are errata regarding adjusting the prescalar and divisor.
+ */
+#undef SLOWDOWN_MASTER_CLOCK
+
+#define MCKRDY_TIMEOUT          1000
+#define MOSCRDY_TIMEOUT         1000
+#define PLLALOCK_TIMEOUT        1000
+#define PLLBLOCK_TIMEOUT        1000
+
+
+/*
+ * Wait until master clock is ready (after switching master clock source)
+ */
+        .macro wait_mckrdy
+        mov     r4, #MCKRDY_TIMEOUT
+1:      sub     r4, r4, #1
+        cmp     r4, #0
+        beq     2f
+        ldr     r3, [r1, #(AT91_PMC_SR - AT91_PMC)]
+        tst     r3, #AT91_PMC_MCKRDY
+        beq     1b
+2:
+        .endm
+
+/*
+ * Wait until master oscillator has stabilized.
+ */
+        .macro wait_moscrdy
+        mov     r4, #MOSCRDY_TIMEOUT
+1:      sub     r4, r4, #1
+        cmp     r4, #0
+        beq     2f
+        ldr     r3, [r1, #(AT91_PMC_SR - AT91_PMC)]
+        tst     r3, #AT91_PMC_MOSCS
+        beq     1b
+2:
+        .endm
+
+/*
+ * Wait until PLLA has locked.
+ */
+        .macro wait_pllalock
+        mov     r4, #PLLALOCK_TIMEOUT
+1:      sub     r4, r4, #1
+        cmp     r4, #0
+        beq     2f
+        ldr     r3, [r1, #(AT91_PMC_SR - AT91_PMC)]
+        tst     r3, #AT91_PMC_LOCKA
+        beq     1b
+2:
+        .endm
+
+/*
+ * Wait until PLLB has locked.
+ */
+        .macro wait_pllblock
+        mov     r4, #PLLBLOCK_TIMEOUT
+1:      sub     r4, r4, #1
+        cmp     r4, #0
+        beq     2f
+        ldr     r3, [r1, #(AT91_PMC_SR - AT91_PMC)]
+        tst     r3, #AT91_PMC_LOCKB
+        beq     1b
+2:
+        .endm
+
+        .text
+
+ENTRY(at91_slow_clock)
+        /* Save registers on stack */
+        stmfd   sp!, {r0 - r12, lr}
+
+        /*
+         * Register usage:
+         *  R1 = Base address of AT91_PMC
+         *  R2 = Base address of AT91_SDRAMC (or AT91_SYS on AT91RM9200)
+         *  R3 = temporary register
+         *  R4 = temporary register
+         */
+        ldr     r1, .at91_va_base_pmc
+        ldr     r2, .at91_va_base_sdramc
+
+        /* Drain write buffer */
+        mcr     p15, 0, r0, c7, c10, 4
+
+#ifdef CONFIG_ARCH_AT91RM9200
+        /* Put SDRAM in self-refresh mode */
+        mov     r3, #1
+        str     r3, [r2, #AT91_SDRAMC_SRR]
+#elif defined(CONFIG_ARCH_AT91CAP9)
+        /* Enable SDRAM self-refresh mode */
+        ldr     r3, [r2, #AT91_DDRSDRC_LPR - AT91_DDRSDRC]
+        str     r3, .saved_sam9_lpr
+
+        mov     r3, #AT91_DDRSDRC_LPCB_SELF_REFRESH
+        str     r3, [r2, #AT91_DDRSDRC_LPR - AT91_DDRSDRC]
+#else
+        /* Enable SDRAM self-refresh mode */
+        ldr     r3, [r2, #AT91_SDRAMC_LPR - AT91_SDRAMC]
+        str     r3, .saved_sam9_lpr
+
+        mov     r3, #AT91_SDRAMC_LPCB_SELF_REFRESH
+        str     r3, [r2, #AT91_SDRAMC_LPR - AT91_SDRAMC]
+#endif
+
+        /* Save Master clock setting */
+        ldr     r3, [r1, #(AT91_PMC_MCKR - AT91_PMC)]
+        str     r3, .saved_mckr
+
+        /*
+         * Set the Master clock source to slow clock
+         */
+        bic     r3, r3, #AT91_PMC_CSS
+        str     r3, [r1, #(AT91_PMC_MCKR - AT91_PMC)]
+
+        wait_mckrdy
+
+#ifdef SLOWDOWN_MASTER_CLOCK
+        /*
+         * Set the Master Clock PRES and MDIV fields.
+         *
+         * See AT91RM9200 errata #27 and #28 for details.
+         */
+        mov     r3, #0
+        str     r3, [r1, #(AT91_PMC_MCKR - AT91_PMC)]
+
+        wait_mckrdy
+#endif
+
+        /* Save PLLA setting and disable it */
+        ldr     r3, [r1, #(AT91_CKGR_PLLAR - AT91_PMC)]
+        str     r3, .saved_pllar
+
+        mov     r3, #AT91_PMC_PLLCOUNT
+        orr     r3, r3, #(1 << 29)              /* bit 29 always set */
+        str     r3, [r1, #(AT91_CKGR_PLLAR - AT91_PMC)]
+
+        wait_pllalock
+
+        /* Save PLLB setting and disable it */
+        ldr     r3, [r1, #(AT91_CKGR_PLLBR - AT91_PMC)]
+        str     r3, .saved_pllbr
+
+        mov     r3, #AT91_PMC_PLLCOUNT
+        str     r3, [r1, #(AT91_CKGR_PLLBR - AT91_PMC)]
+
+        wait_pllblock
+
+        /* Turn off the main oscillator */
+        ldr     r3, [r1, #(AT91_CKGR_MOR - AT91_PMC)]
+        bic     r3, r3, #AT91_PMC_MOSCEN
+        str     r3, [r1, #(AT91_CKGR_MOR - AT91_PMC)]
+
+        /* Wait for interrupt */
+        mcr     p15, 0, r0, c7, c0, 4
+
+        /* Turn on the main oscillator */
+        ldr     r3, [r1, #(AT91_CKGR_MOR - AT91_PMC)]
+        orr     r3, r3, #AT91_PMC_MOSCEN
+        str     r3, [r1, #(AT91_CKGR_MOR - AT91_PMC)]
+
+        wait_moscrdy
+
+        /* Restore PLLB setting */
+        ldr     r3, .saved_pllbr
+        str     r3, [r1, #(AT91_CKGR_PLLBR - AT91_PMC)]
+
+        wait_pllblock
+
+        /* Restore PLLA setting */
+        ldr     r3, .saved_pllar
+        str     r3, [r1, #(AT91_CKGR_PLLAR - AT91_PMC)]
+
+        wait_pllalock
+
+#ifdef SLOWDOWN_MASTER_CLOCK
+        /*
+         * First set PRES if it was not 0,
+         * than set CSS and MDIV fields.
+         *
+         * See AT91RM9200 errata #27 and #28 for details.
+         */
+        ldr     r3, .saved_mckr
+        tst     r3, #AT91_PMC_PRES
+        beq     2f
+        and     r3, r3, #AT91_PMC_PRES
+        str     r3, [r1, #(AT91_PMC_MCKR - AT91_PMC)]
+
+        wait_mckrdy
+#endif
+
+        /*
+         * Restore master clock setting
+         */
+2:      ldr     r3, .saved_mckr
+        str     r3, [r1, #(AT91_PMC_MCKR - AT91_PMC)]
+
+        wait_mckrdy
+
+#ifdef CONFIG_ARCH_AT91RM9200
+        /* Do nothing - self-refresh is automatically disabled. */
+#elif defined(CONFIG_ARCH_AT91CAP9)
+        /* Restore LPR on AT91CAP9 */
+        ldr     r3, .saved_sam9_lpr
+        str     r3, [r2, #AT91_DDRSDRC_LPR - AT91_DDRSDRC]
+#else
+        /* Restore LPR on AT91SAM9 */
+        ldr     r3, .saved_sam9_lpr
+        str     r3, [r2, #AT91_SDRAMC_LPR - AT91_SDRAMC]
+#endif
+
+        /* Restore registers, and return */
+        ldmfd   sp!, {r0 - r12, pc}
+
+
+.saved_mckr:
+        .word 0
+
+.saved_pllar:
+        .word 0
+
+.saved_pllbr:
+        .word 0
+
+.saved_sam9_lpr:
+        .word 0
+
+.at91_va_base_pmc:
+        .word AT91_VA_BASE_SYS + AT91_PMC
+
+#ifdef CONFIG_ARCH_AT91RM9200
+.at91_va_base_sdramc:
+        .word AT91_VA_BASE_SYS
+#elif defined(CONFIG_ARCH_AT91CAP9)
+.at91_va_base_sdramc:
+        .word AT91_VA_BASE_SYS + AT91_DDRSDRC
+#else
+.at91_va_base_sdramc:
+        .word AT91_VA_BASE_SYS + AT91_SDRAMC
+#endif
+
+ENTRY(at91_slow_clock_sz)
+        .word .-at91_slow_clock