davinci: add power management support

This patch adds core power management (suspend-to-RAM)
support for DaVinci SoCs.

The code depends on the the "deepsleep" feature to suspend
the SoC and saves power by gating the input clock.

The wakeup can be based on an external event as supported
by the SoC.

Assembly code (in sleep.S) is added to aid gating DDR2
clocks. Code doing this work should not be accessing DDR2.
The assembly code is relocated to SRAM by the code in pm.c

The support has been validated on DA850/OMAP-L138 only
though the code is (hopefully) generic enough that other
SoCs supporting deepsleep feature simply requires SoC
specific code to start using this driver.

Note that all the device drivers don't support suspend/resume
still and are being worked on.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

1 files changed, 224 insertions, 0 deletions

diff --git a/arch/arm/mach-davinci/sleep.S b/arch/arm/mach-davinci/sleep.S
new file mode 100644
index 0000000..fb5e72b
--- /dev/null
+++ b/arch/arm/mach-davinci/sleep.S
@@ -0,0 +1,224 @@
+/*
+ * (C) Copyright 2009, Texas Instruments, Inc. http://www.ti.com/
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR /PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+/* replicated define because linux/bitops.h cannot be included in assembly */
+#define BIT(nr)			(1 << (nr))
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <mach/psc.h>
+#include <mach/memory.h>
+
+#include "clock.h"
+
+/* Arbitrary, hardware currently does not update PHYRDY correctly */
+#define PHYRDY_CYCLES		0x1000
+
+/* Assume 25 MHz speed for the cycle conversions since PLLs are bypassed */
+#define PLL_BYPASS_CYCLES	(PLL_BYPASS_TIME * 25)
+#define PLL_RESET_CYCLES	(PLL_RESET_TIME	* 25)
+#define PLL_LOCK_CYCLES		(PLL_LOCK_TIME * 25)
+
+#define DEEPSLEEP_SLEEPENABLE_BIT	BIT(31)
+
+	.text
+/*
+ * Move DaVinci into deep sleep state
+ *
+ * Note: This code is copied to internal SRAM by PM code. When the DaVinci
+ *	 wakes up it continues execution at the point it went to sleep.
+ * Register Usage:
+ * 	r0: contains virtual base for DDR2 controller
+ * 	r1: contains virtual base for DDR2 Power and Sleep controller (PSC)
+ * 	r2: contains PSC number for DDR2
+ * 	r3: contains virtual base DDR2 PLL controller
+ * 	r4: contains virtual address of the DEEPSLEEP register
+ */
+ENTRY(davinci_cpu_suspend)
+	stmfd	sp!, {r0-r12, lr}		@ save registers on stack
+
+	ldr 	ip, CACHE_FLUSH
+	blx	ip
+
+	ldmia	r0, {r0-r4}
+
+	/*
+	 * Switch DDR to self-refresh mode.
+	 */
+
+	/* calculate SDRCR address */
+	ldr	ip, [r0, #DDR2_SDRCR_OFFSET]
+	bic	ip, ip, #DDR2_SRPD_BIT
+	orr	ip, ip, #DDR2_LPMODEN_BIT
+	str	ip, [r0, #DDR2_SDRCR_OFFSET]
+
+	ldr	ip, [r0, #DDR2_SDRCR_OFFSET]
+	orr	ip, ip, #DDR2_MCLKSTOPEN_BIT
+	str	ip, [r0, #DDR2_SDRCR_OFFSET]
+
+       mov	ip, #PHYRDY_CYCLES
+1:     subs	ip, ip, #0x1
+       bne	1b
+
+       /* Disable DDR2 LPSC */
+	mov	r7, r0
+	mov	r0, #0x2
+	bl davinci_ddr_psc_config
+	mov	r0, r7
+
+	/* Disable clock to DDR PHY */
+	ldr	ip, [r3, #PLLDIV1]
+	bic	ip, ip, #PLLDIV_EN
+	str	ip, [r3, #PLLDIV1]
+
+	/* Put the DDR PLL in bypass and power down */
+	ldr	ip, [r3, #PLLCTL]
+	bic	ip, ip, #PLLCTL_PLLENSRC
+	bic	ip, ip, #PLLCTL_PLLEN
+	str	ip, [r3, #PLLCTL]
+
+	/* Wait for PLL to switch to bypass */
+       mov	ip, #PLL_BYPASS_CYCLES
+2:     subs	ip, ip, #0x1
+       bne	2b
+
+       /* Power down the PLL */
+	ldr	ip, [r3, #PLLCTL]
+	orr	ip, ip, #PLLCTL_PLLPWRDN
+	str	ip, [r3, #PLLCTL]
+
+	/* Go to deep sleep */
+	ldr	ip, [r4]
+	orr	ip, ip, #DEEPSLEEP_SLEEPENABLE_BIT
+	/* System goes to sleep beyond after this instruction */
+	str	ip, [r4]
+
+	/* Wake up from sleep */
+
+	/* Clear sleep enable */
+	ldr	ip, [r4]
+	bic	ip, ip, #DEEPSLEEP_SLEEPENABLE_BIT
+	str	ip, [r4]
+
+	/* initialize the DDR PLL controller */
+
+	/* Put PLL in reset */
+	ldr	ip, [r3, #PLLCTL]
+	bic	ip, ip, #PLLCTL_PLLRST
+	str	ip, [r3, #PLLCTL]
+
+	/* Clear PLL power down */
+	ldr	ip, [r3, #PLLCTL]
+	bic	ip, ip, #PLLCTL_PLLPWRDN
+	str	ip, [r3, #PLLCTL]
+
+       mov	ip, #PLL_RESET_CYCLES
+3:     subs	ip, ip, #0x1
+       bne	3b
+
+       /* Bring PLL out of reset */
+	ldr	ip, [r3, #PLLCTL]
+	orr	ip, ip, #PLLCTL_PLLRST
+	str	ip, [r3, #PLLCTL]
+
+	/* Wait for PLL to lock (assume prediv = 1, 25MHz OSCIN) */
+       mov	ip, #PLL_LOCK_CYCLES
+4:     subs	ip, ip, #0x1
+       bne	4b
+
+       /* Remove PLL from bypass mode */
+	ldr	ip, [r3, #PLLCTL]
+	bic	ip, ip, #PLLCTL_PLLENSRC
+	orr	ip, ip, #PLLCTL_PLLEN
+	str	ip, [r3, #PLLCTL]
+
+	/* Start 2x clock to DDR2 */
+
+	ldr	ip, [r3, #PLLDIV1]
+	orr	ip, ip, #PLLDIV_EN
+	str	ip, [r3, #PLLDIV1]
+
+	/* Enable VCLK */
+
+       /* Enable DDR2 LPSC */
+	mov	r7, r0
+	mov	r0, #0x3
+	bl davinci_ddr_psc_config
+	mov	r0, r7
+
+	/* clear  MCLKSTOPEN */
+
+	ldr	ip, [r0, #DDR2_SDRCR_OFFSET]
+	bic	ip, ip, #DDR2_MCLKSTOPEN_BIT
+	str	ip, [r0, #DDR2_SDRCR_OFFSET]
+
+	ldr	ip, [r0, #DDR2_SDRCR_OFFSET]
+	bic	ip, ip, #DDR2_LPMODEN_BIT
+	str	ip, [r0, #DDR2_SDRCR_OFFSET]
+
+	/* Restore registers and return */
+	ldmfd   sp!, {r0-r12, pc}
+
+ENDPROC(davinci_cpu_suspend)
+
+/*
+ * Disables or Enables DDR2 LPSC
+ * Register Usage:
+ * 	r0: Enable or Disable LPSC r0 = 0x3 => Enable, r0 = 0x2 => Disable LPSC
+ * 	r1: contains virtual base for DDR2 Power and Sleep controller (PSC)
+ * 	r2: contains PSC number for DDR2
+ */
+ENTRY(davinci_ddr_psc_config)
+	/* Set next state in mdctl for DDR2 */
+	mov	r6, #MDCTL
+	add	r6, r6, r2, lsl #2
+	ldr	ip, [r1, r6]
+	bic	ip, ip, #MDSTAT_STATE_MASK
+	orr	ip, ip, r0
+	str	ip, [r1, r6]
+
+	/* Enable the Power Domain Transition Command */
+	ldr	ip, [r1, #PTCMD]
+	orr	ip, ip, #0x1
+	str	ip, [r1, #PTCMD]
+
+	/* Check for Transition Complete (PTSTAT) */
+ptstat_done:
+	ldr	ip, [r1, #PTSTAT]
+	and	ip, ip, #0x1
+	cmp 	ip, #0x0
+	bne	ptstat_done
+
+	/* Check for DDR2 clock disable completion; */
+	mov	r6, #MDSTAT
+	add	r6, r6, r2, lsl #2
+ddr2clk_stop_done:
+	ldr	ip, [r1, r6]
+	and	ip, ip, #MDSTAT_STATE_MASK
+	cmp	ip, r0
+	bne	ddr2clk_stop_done
+
+	mov	pc, lr
+ENDPROC(davinci_ddr_psc_config)
+
+CACHE_FLUSH:
+	.word	arm926_flush_kern_cache_all
+
+ENTRY(davinci_cpu_suspend_sz)
+	.word	. - davinci_cpu_suspend
+ENDPROC(davinci_cpu_suspend_sz)