ARM: mvebu: Armada XP GP specific suspend/resume code

On the Armada XP GP platform, entering suspend to RAM state is
triggering by talking to an external PIC micro-controller connected to
the SoC using 3 GPIOs. There is then a small magic sequence of GPIO
toggling that needs to be used to tell the PIC to turn off the SoC.

The code uses the Device Tree to find out which GPIOs are used to
connect to the PIC micro-controller, and then registers its
mvebu_armada_xp_gp_pm_enter() callback to the SoC-level PM code. The
SoC PM code will call back into this registered function at the very
end of the suspend procedure.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1416585613-2113-12-git-send-email-thomas.petazzoni@free-electrons.comSigned-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/mach-mvebu/Makefile

@@ -7,7 +7,7 @@ CFLAGS_pmsu.o			:= -march=armv7-a
 obj-$(CONFIG_MACH_MVEBU_ANY)	 += system-controller.o mvebu-soc-id.o
 
 ifeq ($(CONFIG_MACH_MVEBU_V7),y)
-obj-y				 += cpu-reset.o board-v7.o coherency.o coherency_ll.o pmsu.o pmsu_ll.o pm.o
+obj-y				 += cpu-reset.o board-v7.o coherency.o coherency_ll.o pmsu.o pmsu_ll.o pm.o pm-board.o
 obj-$(CONFIG_SMP)		 += platsmp.o headsmp.o platsmp-a9.o headsmp-a9.o
 endif
 

arch/arm/mach-mvebu/pm-board.c

+/*
+ * Board-level suspend/resume support.
+ *
+ * Copyright (C) 2014 Marvell
+ *
+ * Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_gpio.h>
+#include <linux/slab.h>
+#include "common.h"
+
+#define ARMADA_XP_GP_PIC_NR_GPIOS 3
+
+static void __iomem *gpio_ctrl;
+static int pic_gpios[ARMADA_XP_GP_PIC_NR_GPIOS];
+static int pic_raw_gpios[ARMADA_XP_GP_PIC_NR_GPIOS];
+
+static void mvebu_armada_xp_gp_pm_enter(void __iomem *sdram_reg, u32 srcmd)
+{
+	u32 reg, ackcmd;
+	int i;
+
+	/* Put 001 as value on the GPIOs */
+	reg = readl(gpio_ctrl);
+	for (i = 0; i < ARMADA_XP_GP_PIC_NR_GPIOS; i++)
+		reg &= ~BIT(pic_raw_gpios[i]);
+	reg |= BIT(pic_raw_gpios[0]);
+	writel(reg, gpio_ctrl);
+
+	/* Prepare writing 111 to the GPIOs */
+	ackcmd = readl(gpio_ctrl);
+	for (i = 0; i < ARMADA_XP_GP_PIC_NR_GPIOS; i++)
+		ackcmd |= BIT(pic_raw_gpios[i]);
+
+	/*
+	 * Wait a while, the PIC needs quite a bit of time between the
+	 * two GPIO commands.
+	 */
+	mdelay(3000);
+
+	asm volatile (
+		/* Align to a cache line */
+		".balign 32\n\t"
+
+		/* Enter self refresh */
+		"str %[srcmd], [%[sdram_reg]]\n\t"
+
+		/*
+		 * Wait 100 cycles for DDR to enter self refresh, by
+		 * doing 50 times two instructions.
+		 */
+		"mov r1, #50\n\t"
+		"1: subs r1, r1, #1\n\t"
+		"bne 1b\n\t"
+
+		/* Issue the command ACK */
+		"str %[ackcmd], [%[gpio_ctrl]]\n\t"
+
+		/* Trap the processor */
+		"b .\n\t"
+		: : [srcmd] "r" (srcmd), [sdram_reg] "r" (sdram_reg),
+		  [ackcmd] "r" (ackcmd), [gpio_ctrl] "r" (gpio_ctrl) : "r1");
+}
+
+static int mvebu_armada_xp_gp_pm_init(void)
+{
+	struct device_node *np;
+	struct device_node *gpio_ctrl_np;
+	int ret = 0, i;
+
+	if (!of_machine_is_compatible("marvell,axp-gp"))
+		return -ENODEV;
+
+	np = of_find_node_by_name(NULL, "pm_pic");
+	if (!np)
+		return -ENODEV;
+
+	for (i = 0; i < ARMADA_XP_GP_PIC_NR_GPIOS; i++) {
+		char *name;
+		struct of_phandle_args args;
+
+		pic_gpios[i] = of_get_named_gpio(np, "ctrl-gpios", i);
+		if (pic_gpios[i] < 0) {
+			ret = -ENODEV;
+			goto out;
+		}
+
+		name = kasprintf(GFP_KERNEL, "pic-pin%d", i);
+		if (!name) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		ret = gpio_request(pic_gpios[i], name);
+		if (ret < 0) {
+			kfree(name);
+			goto out;
+		}
+
+		ret = gpio_direction_output(pic_gpios[i], 0);
+		if (ret < 0) {
+			gpio_free(pic_gpios[i]);
+			kfree(name);
+			goto out;
+		}
+
+		ret = of_parse_phandle_with_fixed_args(np, "ctrl-gpios", 2,
+						       i, &args);
+		if (ret < 0) {
+			gpio_free(pic_gpios[i]);
+			kfree(name);
+			goto out;
+		}
+
+		gpio_ctrl_np = args.np;
+		pic_raw_gpios[i] = args.args[0];
+	}
+
+	gpio_ctrl = of_iomap(gpio_ctrl_np, 0);
+	if (!gpio_ctrl)
+		return -ENOMEM;
+
+	mvebu_pm_init(mvebu_armada_xp_gp_pm_enter);
+
+out:
+	of_node_put(np);
+	return ret;
+}
+
+late_initcall(mvebu_armada_xp_gp_pm_init);