[ARM] Orion: implement power-off method for QNAP TS-109/209

Since the PIC is attached to UART1, it doesn't need a kernel device driver
of its own; but powering off is something that the kernel should do, so
this patch forcefully configures the UART1 for 19200 baud and sends the
character that tells the PIC to cut the power.
Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Cc: Byron Bradley <byron.bbradley@gmail.com>
Acked-by: Nicolas Pitre <nico@marvell.com>

arch/arm/mach-orion/ts209-setup.c

@@ -20,6 +20,7 @@
 #include <linux/gpio_keys.h>
 #include <linux/input.h>
 #include <linux/i2c.h>
+#include <linux/serial_reg.h>
 #include <asm/mach-types.h>
 #include <asm/gpio.h>
 #include <asm/mach/arch.h>
@@ -239,6 +240,32 @@ static struct platform_device *qnap_ts209_devices[] __initdata = {
 	&qnap_ts209_button_device,
 };
 
+/*
+ * QNAP TS-[12]09 specific power off method via UART1-attached PIC
+ */
+
+#define UART1_REG(x)  (UART1_BASE + ((UART_##x) << 2))
+
+static void qnap_ts209_power_off(void)
+{
+	/* 19200 baud divisor */
+	const unsigned divisor = ((ORION_TCLK + (8 * 19200)) / (16 * 19200));
+
+	pr_info("%s: triggering power-off...\n", __func__);
+
+	/* hijack uart1 and reset into sane state (19200,8n1) */
+	orion_write(UART1_REG(LCR), 0x83);
+	orion_write(UART1_REG(DLL), divisor & 0xff);
+	orion_write(UART1_REG(DLM), (divisor >> 8) & 0xff);
+	orion_write(UART1_REG(LCR), 0x03);
+	orion_write(UART1_REG(IER), 0x00);
+	orion_write(UART1_REG(FCR), 0x00);
+	orion_write(UART1_REG(MCR), 0x00);
+
+	/* send the power-off command 'A' to PIC */
+	orion_write(UART1_REG(TX), 'A');
+}
+
 static void __init qnap_ts209_init(void)
 {
 	/*
@@ -287,6 +314,9 @@ static void __init qnap_ts209_init(void)
 	orion_write(MPP_16_19_CTRL, 0x5500);
 	orion_gpio_set_valid_pins(0x3cc0fff);
 
+	/* register ts209 specific power-off method */
+	pm_power_off = qnap_ts209_power_off;
+
 	platform_add_devices(qnap_ts209_devices,
 				ARRAY_SIZE(qnap_ts209_devices));
 	i2c_register_board_info(0, &qnap_ts209_i2c_rtc, 1);