[RFC/PATCH 2/2] ARM: kirkwood: Add basic suspend-to-RAM support

[Ezequiel Garcia]

Implements suspend-to-RAM support in a standby-like fashion:
when the SoC enters suspend state the peripheral clocks are gated
and the memory PM units are disabled.

However the network controller clock is not gated for now, since there is
still some work to be done in the driver to provide proper suspend/resume
operations.

Signed-off-by: Simon Guinot <sguinot at lacie.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia at free-electrons.com>
---
 arch/arm/mach-kirkwood/Makefile                   |  1 +
 arch/arm/mach-kirkwood/include/mach/bridge-regs.h |  2 +
 arch/arm/mach-kirkwood/pm.c                       | 83 +++++++++++++++++++++++
 3 files changed, 86 insertions(+)
 create mode 100644 arch/arm/mach-kirkwood/pm.c

diff --git a/arch/arm/mach-kirkwood/Makefile b/arch/arm/mach-kirkwood/Makefile
index e1f3735..2c56aa0 100644
--- a/arch/arm/mach-kirkwood/Makefile
+++ b/arch/arm/mach-kirkwood/Makefile
@@ -1,4 +1,5 @@
 obj-y				+= common.o irq.o pcie.o mpp.o
+obj-$(CONFIG_PM)		+= pm.o
 
 obj-$(CONFIG_MACH_D2NET_V2)		+= d2net_v2-setup.o lacie_v2-common.o
 obj-$(CONFIG_MACH_DB88F6281_BP)		+= db88f6281-bp-setup.o
diff --git a/arch/arm/mach-kirkwood/include/mach/bridge-regs.h b/arch/arm/mach-kirkwood/include/mach/bridge-regs.h
index 5c82b7d..fad3a35 100644
--- a/arch/arm/mach-kirkwood/include/mach/bridge-regs.h
+++ b/arch/arm/mach-kirkwood/include/mach/bridge-regs.h
@@ -78,4 +78,6 @@
 #define CGC_TDM			(1 << 20)
 #define CGC_RESERVED		(0x6 << 21)
 
+#define MEMORY_PM_CTRL		(BRIDGE_VIRT_BASE + 0x118)
+
 #endif
diff --git a/arch/arm/mach-kirkwood/pm.c b/arch/arm/mach-kirkwood/pm.c
new file mode 100644
index 0000000..5624b66
--- /dev/null
+++ b/arch/arm/mach-kirkwood/pm.c
@@ -0,0 +1,83 @@
+/*
+ * Power Management driver for Marvell Kirkwood SoCs
+ *
+ * Copyright (C) 2013 Ezequiel Garcia <ezequiel.garcia at free-electrons.com>
+ * Copyright (C) 2010 Simon Guinot <sguinot at lacie.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 of the License.
+ *
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/suspend.h>
+#include <linux/io.h>
+#include <mach/bridge-regs.h>
+
+
+static void __iomem *ddr_operation_base;
+
+static void kirkwood_suspend_mem(void)
+{
+	u32 clk_ctrl, mem_pm_ctrl;
+
+	clk_ctrl = readl(CLOCK_GATING_CTRL);
+	mem_pm_ctrl = readl(MEMORY_PM_CTRL);
+
+	/*
+	 * Gate clocks, except for so-called 'Runit' unit, which apparently
+	 * corresponds to NAND, SPI and BootROM.
+	 *
+	 * Also, we skip the gating of the GE0 and GE1 clocks for now.
+	 *
+	 * Contrary to my expectation, the SDRAM clock can also be disabled and
+	 * the suspend-resume cycle will complete successfully.
+	 */
+	writel(CGC_GE1 | CGC_GE0 | CGC_RUNIT, CLOCK_GATING_CTRL);
+
+	/* Set peripherals to low-power mode */
+	writel(~0, MEMORY_PM_CTRL);
+
+	/*
+	 * Set DDR in self-refresh.
+	 */
+	writel(0x7, ddr_operation_base);
+
+	/*
+	 * Set CPU in wait-for-interrupt state.
+	 */
+	cpu_do_idle();
+
+	writel(mem_pm_ctrl, MEMORY_PM_CTRL);
+	writel(clk_ctrl, CLOCK_GATING_CTRL);
+}
+
+static int kirkwood_suspend_enter(suspend_state_t state)
+{
+	switch (state) {
+	case PM_SUSPEND_MEM:
+		kirkwood_suspend_mem();
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static const struct platform_suspend_ops kirkwood_suspend_ops = {
+	.enter = kirkwood_suspend_enter,
+	.valid = suspend_valid_only_mem,
+};
+
+static int __init kirkwood_pm_init(void)
+{
+	ddr_operation_base = ioremap(DDR_OPERATION_BASE, 4);
+	suspend_set_ops(&kirkwood_suspend_ops);
+	return 0;
+}
+arch_initcall(kirkwood_pm_init);
-- 
1.8.1.5