avr32: Power Management support ("standby" and "mem" modes)

Implement Standby support. In this mode, we'll suspend all drivers,
put the SDRAM in self-refresh mode and switch off the HSB bus
("frozen" mode.)

Implement Suspend-to-mem support. In this mode, we suspend all
drivers, put the SDRAM into self-refresh mode and switch off all
internal clocks except the 32 kHz oscillator ("stop" mode.)

The lowest-level suspend code runs from a small portion of SRAM
allocated at startup time. This gets rid of a small potential race
with the SDRAM where we might try to enter self-refresh mode in the
middle of an icache burst. We also relocate all interrupt and
exception handlers to SRAM during the small window when we enter and
exit the low-power modes.

We don't need to do any special tricks to start and stop the PLL. The
main clock is automatically gated by hardware until the PLL is stable.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

1 files changed, 108 insertions, 0 deletions

diff --git a/arch/avr32/mach-at32ap/pm-at32ap700x.S b/arch/avr32/mach-at32ap/pm-at32ap700x.S
index 949e2485e27..0a53ad314ff 100644
--- a/arch/avr32/mach-at32ap/pm-at32ap700x.S
+++ b/arch/avr32/mach-at32ap/pm-at32ap700x.S
@@ -12,6 +12,12 @@
 #include <asm/thread_info.h>
 #include <asm/arch/pm.h>
 
+#include "pm.h"
+#include "sdramc.h"
+
+/* Same as 0xfff00000 but fits in a 21 bit signed immediate */
+#define PM_BASE	-0x100000
+
 	.section .bss, "wa", @nobits
 	.global	disable_idle_sleep
 	.type	disable_idle_sleep, @object
@@ -64,3 +70,105 @@ cpu_idle_skip_sleep:
 	unmask_interrupts
 	retal	r12
 	.size	cpu_idle_skip_sleep, . - cpu_idle_skip_sleep
+
+#ifdef CONFIG_PM
+	.section .init.text, "ax", @progbits
+
+	.global	pm_exception
+	.type	pm_exception, @function
+pm_exception:
+	/*
+	 * Exceptions are masked when we switch to this handler, so
+	 * we'll only get "unrecoverable" exceptions (offset 0.)
+	 */
+	sub	r12, pc, . - .Lpanic_msg
+	lddpc	pc, .Lpanic_addr
+
+	.align	2
+.Lpanic_addr:
+	.long	panic
+.Lpanic_msg:
+	.asciz	"Unrecoverable exception during suspend\n"
+	.size	pm_exception, . - pm_exception
+
+	.global	pm_irq0
+	.type	pm_irq0, @function
+pm_irq0:
+	/* Disable interrupts and return after the sleep instruction */
+	mfsr	r9, SYSREG_RSR_INT0
+	mtsr	SYSREG_RAR_INT0, r8
+	sbr	r9, SYSREG_GM_OFFSET
+	mtsr	SYSREG_RSR_INT0, r9
+	rete
+
+	/*
+	 * void cpu_enter_standby(unsigned long sdramc_base)
+	 *
+	 * Enter PM_SUSPEND_STANDBY mode. At this point, all drivers
+	 * are suspended and interrupts are disabled. Interrupts
+	 * marked as 'wakeup' event sources may still come along and
+	 * get us out of here.
+	 *
+	 * The SDRAM will be put into self-refresh mode (which does
+	 * not require a clock from the CPU), and the CPU will be put
+	 * into "frozen" mode (HSB bus stopped). The SDRAM controller
+	 * will automatically bring the SDRAM into normal mode on the
+	 * first access, and the power manager will automatically
+	 * start the HSB and CPU clocks upon a wakeup event.
+	 *
+	 * This code uses the same "skip sleep" technique as above.
+	 * It is very important that we jump directly to
+	 * cpu_after_sleep after the sleep instruction since that's
+	 * where we'll end up if the interrupt handler decides that we
+	 * need to skip the sleep instruction.
+	 */
+	.global	pm_standby
+	.type	pm_standby, @function
+pm_standby:
+	/*
+	 * interrupts are already masked at this point, and EVBA
+	 * points to pm_exception above.
+	 */
+	ld.w	r10, r12[SDRAMC_LPR]
+	sub	r8, pc, . - 1f		/* return address for irq handler */
+	mov	r11, SDRAMC_LPR_LPCB_SELF_RFR
+	bfins	r10, r11, 0, 2		/* LPCB <- self Refresh */
+	sync	0			/* flush write buffer */
+	st.w	r12[SDRAMC_LPR], r11	/* put SDRAM in self-refresh mode */
+	ld.w	r11, r12[SDRAMC_LPR]
+	unmask_interrupts
+	sleep	CPU_SLEEP_FROZEN
+1:	mask_interrupts
+	retal	r12
+	.size	pm_standby, . - pm_standby
+
+	.global	pm_suspend_to_ram
+	.type	pm_suspend_to_ram, @function
+pm_suspend_to_ram:
+	/*
+	 * interrupts are already masked at this point, and EVBA
+	 * points to pm_exception above.
+	 */
+	mov	r11, 0
+	cache	r11[2], 8		/* clean all dcache lines */
+	sync	0			/* flush write buffer */
+	ld.w	r10, r12[SDRAMC_LPR]
+	sub	r8, pc, . - 1f		/* return address for irq handler */
+	mov	r11, SDRAMC_LPR_LPCB_SELF_RFR
+	bfins	r10, r11, 0, 2		/* LPCB <- self refresh */
+	st.w	r12[SDRAMC_LPR], r10	/* put SDRAM in self-refresh mode */
+	ld.w	r11, r12[SDRAMC_LPR]
+
+	unmask_interrupts
+	sleep	CPU_SLEEP_STOP
+1:	mask_interrupts
+
+	retal	r12
+	.size	pm_suspend_to_ram, . - pm_suspend_to_ram
+
+	.global	pm_sram_end
+	.type	pm_sram_end, @function
+pm_sram_end:
+	.size	pm_sram_end, 0
+
+#endif /* CONFIG_PM */