spi: sprd: Add the support of restarting the system

On Spreadtrum platform, we use one PMIC watchdog to reset the whole system
with loading one suitable timeout value (usually 50ms) for the watchdog.

In theory, we should implement the restart function in drivers/power/reset
subsystem to access the PMIC watchdog with regmap. When restart the system,
other cores will be stopped by IPI, but if other cores were accessing PMIC
with holding the regmap mutex lock, that will cause dead-lock issue if we
try to access the PMIC watchdog with regmap to restart the whole system.
Thus we can implement the restart function in ADI driver to avoid this
issue.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 112 insertions, 0 deletions

diff --git a/drivers/spi/spi-sprd-adi.c b/drivers/spi/spi-sprd-adi.c
index 74bbd045aac0..197d4b0d81af 100644
--- a/drivers/spi/spi-sprd-adi.c
+++ b/drivers/spi/spi-sprd-adi.c
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: GPL-2.0
  */
 
+#include <linux/delay.h>
 #include <linux/hwspinlock.h>
 #include <linux/init.h>
 #include <linux/io.h>
@@ -12,6 +13,7 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
+#include <linux/reboot.h>
 #include <linux/spi/spi.h>
 #include <linux/sizes.h>
 
@@ -67,6 +69,40 @@
 #define ADI_READ_TIMEOUT                2000
 #define REG_ADDR_LOW_MASK               GENMASK(11, 0)
 
+/* Registers definitions for PMIC watchdog controller */
+#define REG_WDG_LOAD_LOW                0x80
+#define REG_WDG_LOAD_HIGH               0x84
+#define REG_WDG_CTRL                    0x88
+#define REG_WDG_LOCK                    0xa0
+
+/* Bits definitions for register REG_WDG_CTRL */
+#define BIT_WDG_RUN                     BIT(1)
+#define BIT_WDG_RST                     BIT(3)
+
+/* Registers definitions for PMIC */
+#define PMIC_RST_STATUS                 0xee8
+#define PMIC_MODULE_EN                  0xc08
+#define PMIC_CLK_EN                     0xc18
+#define BIT_WDG_EN                      BIT(2)
+
+/* Definition of PMIC reset status register */
+#define HWRST_STATUS_RECOVERY           0x20
+#define HWRST_STATUS_NORMAL             0x40
+#define HWRST_STATUS_ALARM              0x50
+#define HWRST_STATUS_SLEEP              0x60
+#define HWRST_STATUS_FASTBOOT           0x30
+#define HWRST_STATUS_SPECIAL            0x70
+#define HWRST_STATUS_PANIC              0x80
+#define HWRST_STATUS_CFTREBOOT          0x90
+#define HWRST_STATUS_AUTODLOADER        0xa0
+#define HWRST_STATUS_IQMODE             0xb0
+#define HWRST_STATUS_SPRDISK            0xc0
+
+/* Use default timeout 50 ms that converts to watchdog values */
+#define WDG_LOAD_VAL                    ((50 * 1000) / 32768)
+#define WDG_LOAD_MASK                   GENMASK(15, 0)
+#define WDG_UNLOCK_KEY                  0xe551
+
 struct sprd_adi {
         struct spi_controller   *ctlr;
         struct device           *dev;
@@ -74,6 +110,7 @@ struct sprd_adi {
         struct hwspinlock       *hwlock;
         unsigned long           slave_vbase;
         unsigned long           slave_pbase;
+        struct notifier_block   restart_handler;
 };
 
 static int sprd_adi_check_paddr(struct sprd_adi *sadi, u32 paddr)
@@ -270,6 +307,72 @@ static int sprd_adi_transfer_one(struct spi_controller *ctlr,
         return 0;
 }
 
+static int sprd_adi_restart_handler(struct notifier_block *this,
+                                    unsigned long mode, void *cmd)
+{
+        struct sprd_adi *sadi = container_of(this, struct sprd_adi,
+                                             restart_handler);
+        u32 val, reboot_mode = 0;
+
+        if (!cmd)
+                reboot_mode = HWRST_STATUS_NORMAL;
+        else if (!strncmp(cmd, "recovery", 8))
+                reboot_mode = HWRST_STATUS_RECOVERY;
+        else if (!strncmp(cmd, "alarm", 5))
+                reboot_mode = HWRST_STATUS_ALARM;
+        else if (!strncmp(cmd, "fastsleep", 9))
+                reboot_mode = HWRST_STATUS_SLEEP;
+        else if (!strncmp(cmd, "bootloader", 10))
+                reboot_mode = HWRST_STATUS_FASTBOOT;
+        else if (!strncmp(cmd, "panic", 5))
+                reboot_mode = HWRST_STATUS_PANIC;
+        else if (!strncmp(cmd, "special", 7))
+                reboot_mode = HWRST_STATUS_SPECIAL;
+        else if (!strncmp(cmd, "cftreboot", 9))
+                reboot_mode = HWRST_STATUS_CFTREBOOT;
+        else if (!strncmp(cmd, "autodloader", 11))
+                reboot_mode = HWRST_STATUS_AUTODLOADER;
+        else if (!strncmp(cmd, "iqmode", 6))
+                reboot_mode = HWRST_STATUS_IQMODE;
+        else if (!strncmp(cmd, "sprdisk", 7))
+                reboot_mode = HWRST_STATUS_SPRDISK;
+        else
+                reboot_mode = HWRST_STATUS_NORMAL;
+
+        /* Record the reboot mode */
+        sprd_adi_read(sadi, sadi->slave_pbase + PMIC_RST_STATUS, &val);
+        val |= reboot_mode;
+        sprd_adi_write(sadi, sadi->slave_pbase + PMIC_RST_STATUS, val);
+
+        /* Enable the interface clock of the watchdog */
+        sprd_adi_read(sadi, sadi->slave_pbase + PMIC_MODULE_EN, &val);
+        val |= BIT_WDG_EN;
+        sprd_adi_write(sadi, sadi->slave_pbase + PMIC_MODULE_EN, val);
+
+        /* Enable the work clock of the watchdog */
+        sprd_adi_read(sadi, sadi->slave_pbase + PMIC_CLK_EN, &val);
+        val |= BIT_WDG_EN;
+        sprd_adi_write(sadi, sadi->slave_pbase + PMIC_CLK_EN, val);
+
+        /* Unlock the watchdog */
+        sprd_adi_write(sadi, sadi->slave_pbase + REG_WDG_LOCK, WDG_UNLOCK_KEY);
+
+        /* Load the watchdog timeout value, 50ms is always enough. */
+        sprd_adi_write(sadi, sadi->slave_pbase + REG_WDG_LOAD_LOW,
+                       WDG_LOAD_VAL & WDG_LOAD_MASK);
+        sprd_adi_write(sadi, sadi->slave_pbase + REG_WDG_LOAD_HIGH, 0);
+
+        /* Start the watchdog to reset system */
+        sprd_adi_read(sadi, sadi->slave_pbase + REG_WDG_CTRL, &val);
+        val |= BIT_WDG_RUN | BIT_WDG_RST;
+        sprd_adi_write(sadi, sadi->slave_pbase + REG_WDG_CTRL, val);
+
+        mdelay(1000);
+
+        dev_emerg(sadi->dev, "Unable to restart system\n");
+        return NOTIFY_DONE;
+}
+
 static void sprd_adi_hw_init(struct sprd_adi *sadi)
 {
         struct device_node *np = sadi->dev->of_node;
@@ -383,6 +486,14 @@ static int sprd_adi_probe(struct platform_device *pdev)
                 goto free_hwlock;
         }
 
+        sadi->restart_handler.notifier_call = sprd_adi_restart_handler;
+        sadi->restart_handler.priority = 128;
+        ret = register_restart_handler(&sadi->restart_handler);
+        if (ret) {
+                dev_err(&pdev->dev, "can not register restart handler\n");
+                goto free_hwlock;
+        }
+
         return 0;
 
 free_hwlock:
@@ -397,6 +508,7 @@ static int sprd_adi_remove(struct platform_device *pdev)
         struct spi_controller *ctlr = dev_get_drvdata(&pdev->dev);
         struct sprd_adi *sadi = spi_controller_get_devdata(ctlr);
 
+        unregister_restart_handler(&sadi->restart_handler);
         hwspin_lock_free(sadi->hwlock);
         return 0;
 }