[PATCH v1 6/6] soc/tegra: pmc: Add power off handler

[Dmitry Osipenko <digetx@gmail.com>]

Nexus 7 Android tablet can be turned off using a special bootloader
command which is conveyed to bootloader by putting magic value into
specific scratch register and then rebooting normally. This power off
method should be invoked if USB cable is connected. Bootloader then will
display battery status and power off the device. This behaviour is
borrowed from downstream kernel and matches user expectations, otherwise
it looks like device got hung during power off.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/soc/tegra/pmc.c | 42 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
index dc9ad075ee4a..44de043c2012 100644
--- a/drivers/soc/tegra/pmc.c
+++ b/drivers/soc/tegra/pmc.c
@@ -39,6 +39,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_domain.h>
 #include <linux/pm_opp.h>
+#include <linux/power_supply.h>
 #include <linux/reboot.h>
 #include <linux/regmap.h>
 #include <linux/reset.h>
@@ -107,6 +108,7 @@
 #define PMC_USB_DEBOUNCE_DEL		0xec
 #define PMC_USB_AO			0xf0
 
+#define PMC_SCRATCH37			0x130
 #define PMC_SCRATCH41			0x140
 
 #define PMC_WAKE2_MASK			0x160
@@ -1063,10 +1065,8 @@ int tegra_pmc_cpu_remove_clamping(unsigned int cpuid)
 	return tegra_powergate_remove_clamping(id);
 }
 
-static int tegra_pmc_restart_notify(struct notifier_block *this,
-				    unsigned long action, void *data)
+static void tegra_pmc_restart(const char *cmd)
 {
-	const char *cmd = data;
 	u32 value;
 
 	value = tegra_pmc_scratch_readl(pmc, pmc->soc->regs->scratch0);
@@ -1089,6 +1089,12 @@ static int tegra_pmc_restart_notify(struct notifier_block *this,
 	value = tegra_pmc_readl(pmc, PMC_CNTRL);
 	value |= PMC_CNTRL_MAIN_RST;
 	tegra_pmc_writel(pmc, value, PMC_CNTRL);
+}
+
+static int tegra_pmc_restart_notify(struct notifier_block *this,
+				    unsigned long action, void *data)
+{
+	tegra_pmc_restart(data);
 
 	return NOTIFY_DONE;
 }
@@ -1098,6 +1104,29 @@ static struct notifier_block tegra_pmc_restart_handler = {
 	.priority = 128,
 };
 
+static int tegra_pmc_poweroff_notify(struct notifier_block *this,
+				     unsigned long action, void *data)
+{
+	/*
+	 * Reboot Nexus 7 into special bootloader mode if USB cable is
+	 * connected in order to display battery status and power off.
+	 */
+	if (of_machine_is_compatible("asus,grouper") &&
+	    power_supply_is_system_supplied()) {
+		const u32 go_to_charger_mode = 0xa5a55a5a;
+
+		tegra_pmc_writel(pmc, go_to_charger_mode, PMC_SCRATCH37);
+		tegra_pmc_restart(NULL);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block tegra_pmc_poweroff_handler = {
+	.notifier_call = tegra_pmc_poweroff_notify,
+	.priority = 200,
+};
+
 static int powergate_show(struct seq_file *s, void *data)
 {
 	unsigned int i;
@@ -2866,6 +2895,13 @@ static int tegra_pmc_probe(struct platform_device *pdev)
 		return err;
 	}
 
+	err = devm_register_poweroff_handler(&pdev->dev, &tegra_pmc_poweroff_handler);
+	if (err) {
+		dev_err(&pdev->dev, "unable to register poweroff handler, %d\n",
+			err);
+		return err;
+	}
+
 	/*
 	 * PCLK clock rate can't be retrieved using CLK API because it
 	 * causes lockup if CPU enters LP2 idle state from some other
-- 
2.32.0