rpi3: Implement PSCI_SYSTEM_OFF

This implementation doesn't actually turn the system off, it simply
reboots it and prevents it from booting while keeping it in a low power
mode.

Change-Id: I7f72c9f43f25ba0341db052bc2be4774c88a7ea3
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

plat/rpi3/rpi3_hw.h

 /*
- * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -16,13 +16,6 @@
 #define RPI3_IO_BASE			ULL(0x3F000000)
 #define RPI3_IO_SIZE			ULL(0x01000000)
 
-/*
- * Serial port (called 'Mini UART' in the BCM docucmentation).
- */
-#define RPI3_IO_MINI_UART_OFFSET	ULL(0x00215040)
-#define RPI3_MINI_UART_BASE		(RPI3_IO_BASE + RPI3_IO_MINI_UART_OFFSET)
-#define RPI3_MINI_UART_CLK_IN_HZ	ULL(500000000)
-
 /*
  * Power management, reset controller, watchdog.
  */
@@ -30,11 +23,26 @@
 #define RPI3_PM_BASE			(RPI3_IO_BASE + RPI3_IO_PM_OFFSET)
 /* Registers on top of RPI3_PM_BASE. */
 #define RPI3_PM_RSTC_OFFSET		ULL(0x0000001C)
+#define RPI3_PM_RSTS_OFFSET		ULL(0x00000020)
 #define RPI3_PM_WDOG_OFFSET		ULL(0x00000024)
 /* Watchdog constants */
-#define RPI3_PM_PASSWORD		ULL(0x5A000000)
-#define RPI3_PM_RSTC_WRCFG_MASK		ULL(0x00000030)
-#define RPI3_PM_RSTC_WRCFG_FULL_RESET	ULL(0x00000020)
+#define RPI3_PM_PASSWORD		U(0x5A000000)
+#define RPI3_PM_RSTC_WRCFG_MASK		U(0x00000030)
+#define RPI3_PM_RSTC_WRCFG_FULL_RESET	U(0x00000020)
+/*
+ * The RSTS register is used by the VideoCore firmware when booting the
+ * Raspberry Pi to know which partition to boot from. The partition value is
+ * formed by bits 0, 2, 4, 6, 8 and 10. Partition 63 is used by said firmware
+ * to indicate halt.
+ */
+#define RPI3_PM_RSTS_WRCFG_HALT		U(0x00000555)
+
+/*
+ * Serial port (called 'Mini UART' in the BCM docucmentation).
+ */
+#define RPI3_IO_MINI_UART_OFFSET	ULL(0x00215040)
+#define RPI3_MINI_UART_BASE		(RPI3_IO_BASE + RPI3_IO_MINI_UART_OFFSET)
+#define RPI3_MINI_UART_CLK_IN_HZ	ULL(500000000)
 
 /*
  * Local interrupt controller

plat/rpi3/rpi3_pm.c

 /*
- * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -150,41 +150,61 @@ void rpi3_pwr_domain_on_finish(const psci_power_state_t *target_state)
 }
 
 /*******************************************************************************
- * Platform handler to reboot the system
+ * Platform handlers for system reset and system off.
  ******************************************************************************/
-#define RESET_TIMEOUT	10
 
-static void __dead2 rpi3_system_reset(void)
-{
-	/* Setup watchdog for reset */
+/* 10 ticks (Watchdog timer = Timer clock / 16) */
+#define RESET_TIMEOUT	U(10)
 
-	static const uintptr_t base = RPI3_PM_BASE;
+static void __dead2 rpi3_watchdog_reset(void)
+{
 	uint32_t rstc;
 
-	INFO("rpi3: PSCI System Reset: invoking watchdog reset\n");
-
 	console_flush();
 
-	rstc = mmio_read_32(base + RPI3_PM_RSTC_OFFSET);
-	rstc &= ~RPI3_PM_RSTC_WRCFG_MASK;
-	rstc |= RPI3_PM_RSTC_WRCFG_FULL_RESET;
-
-	dmbst();
+	dsbsy();
+	isb();
 
-	/*
-	 * Watchdog timer = Timer clock / 16
-	 * Password (31:16) | Value (11:0)
-	 */
-	mmio_write_32(base + RPI3_PM_WDOG_OFFSET,
+	mmio_write_32(RPI3_PM_BASE + RPI3_PM_WDOG_OFFSET,
 		      RPI3_PM_PASSWORD | RESET_TIMEOUT);
-	mmio_write_32(base + RPI3_PM_RSTC_OFFSET,
-		      RPI3_PM_PASSWORD | rstc);
+
+	rstc = mmio_read_32(RPI3_PM_BASE + RPI3_PM_RSTC_OFFSET);
+	rstc &= ~RPI3_PM_RSTC_WRCFG_MASK;
+	rstc |= RPI3_PM_PASSWORD | RPI3_PM_RSTC_WRCFG_FULL_RESET;
+	mmio_write_32(RPI3_PM_BASE + RPI3_PM_RSTC_OFFSET, rstc);
 
 	for (;;) {
 		wfi();
 	}
 }
 
+static void __dead2 rpi3_system_reset(void)
+{
+	INFO("rpi3: PSCI_SYSTEM_RESET: Invoking watchdog reset\n");
+
+	rpi3_watchdog_reset();
+}
+
+static void __dead2 rpi3_system_off(void)
+{
+	uint32_t rsts;
+
+	INFO("rpi3: PSCI_SYSTEM_OFF: Invoking watchdog reset\n");
+
+	/*
+	 * This function doesn't actually make the Raspberry Pi turn itself off,
+	 * the hardware doesn't allow it. It simply reboots it and the RSTS
+	 * value tells the bootcode.bin firmware not to continue the regular
+	 * bootflow and to stay in a low power mode.
+	 */
+
+	rsts = mmio_read_32(RPI3_PM_BASE + RPI3_PM_RSTS_OFFSET);
+	rsts |= RPI3_PM_PASSWORD | RPI3_PM_RSTS_WRCFG_HALT;
+	mmio_write_32(RPI3_PM_BASE + RPI3_PM_RSTS_OFFSET, rsts);
+
+	rpi3_watchdog_reset();
+}
+
 /*******************************************************************************
  * Platform handlers and setup function.
  ******************************************************************************/
@@ -192,6 +212,7 @@ static const plat_psci_ops_t plat_rpi3_psci_pm_ops = {
 	.cpu_standby = rpi3_cpu_standby,
 	.pwr_domain_on = rpi3_pwr_domain_on,
 	.pwr_domain_on_finish = rpi3_pwr_domain_on_finish,
+	.system_off = rpi3_system_off,
 	.system_reset = rpi3_system_reset,
 	.validate_power_state = rpi3_validate_power_state,
 };