On 07/05/2016 06:22 AM, Stefan Christ wrote:
Signed-off-by: Stefan Christ <s.christ@xxxxxxxxx>
---
I am not sure if I like the idea of bypassing the reboot handler functionality
implemented in the watchdog core. First preference should be to fix it if there
is a use case which is not covered. If that does not work, I would expect
a detailed explanation of the reason, not a patch with no explanation whatsoever.
Guenter
drivers/watchdog/da9063_wdt.c | 87 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 81 insertions(+), 6 deletions(-)
diff --git a/drivers/watchdog/da9063_wdt.c b/drivers/watchdog/da9063_wdt.c
index a32f2cd..b9feef9 100644
--- a/drivers/watchdog/da9063_wdt.c
+++ b/drivers/watchdog/da9063_wdt.c
@@ -18,6 +18,7 @@
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/delay.h>
+#include <linux/i2c.h>
#include <linux/mfd/da9063/registers.h>
#include <linux/mfd/da9063/core.h>
#include <linux/reboot.h>
@@ -41,6 +42,7 @@ struct da9063_watchdog {
struct da9063 *da9063;
struct watchdog_device wdtdev;
struct notifier_block restart_handler;
+ struct notifier_block reboot_notifier;
struct delayed_work ping_work;
unsigned long j_time_stamp;
};
@@ -188,19 +190,83 @@ static int da9063_wdt_set_timeout(struct watchdog_device *wdd,
return ret;
}
+static int da9063_wdt_reboot_notifier(struct notifier_block *this, unsigned long val, void *v)
+{
+ struct da9063_watchdog *wdt = container_of(this,
+ struct da9063_watchdog,
+ reboot_notifier);
+ struct i2c_adapter *adap = wdt->da9063->i2c->adapter;
+
+ /*
+ * First block the I2C bus for other drivers. Other consumers are not
+ * allowed to access the bus now.
+ */
+ adap->blocked = true;
+
+ /*
+ * Then acquire adapter lock. This will wait until all other consumers
+ * have finished. After that no more writes are possible for other
+ * drivers.
+ */
+ i2c_lock_adapter(adap);
+
+ /*
+ * Now the I2C adapter can be used in contexts that are not allowed to
+ * wait for locks or call schedule() because there is no other
+ * consumer.
+ */
+ return NOTIFY_DONE;
+}
+
static int da9063_wdt_restart_handler(struct notifier_block *this,
unsigned long mode, void *cmd)
{
struct da9063_watchdog *wdt = container_of(this,
struct da9063_watchdog,
restart_handler);
- int ret;
+ int ret, i;
+ struct i2c_adapter *adap = wdt->da9063->i2c->adapter;
+ unsigned char data[3] = {DA9063_REG_CONTROL_F,
+ DA9063_SHUTDOWN,
+ 0x0};
+ struct i2c_msg msg = { .addr = wdt->da9063->i2c->addr,
+ .flags = 0,
+ .len = sizeof(data),
+ .buf = data };
+
+ /* Very special calling context:
+ * - other CPU cores already stopped
+ * - But tasks on first cpu still running
+ * - Other tasks may have acquired locks that will never be released
+ * - Cleanup doesn't matter anymore. Execution may stop at any
+ * instruction now.
+ * - Current task can stall the CPU. Not to worried about
+ * concurrent access from other tasks or CPUs.
+ * - You have to avoid any kernel internal function which calls
+ * schedule(). Otherwise other tasks will run and interfere.
+ */
- ret = regmap_write(wdt->da9063->regmap, DA9063_REG_CONTROL_F,
- DA9063_SHUTDOWN);
- if (ret)
- dev_alert(wdt->da9063->dev, "Failed to shutdown (err = %d)\n",
- ret);
+ if (!adap->algo->master_xfer_blocking) {
+ printk("%s: I2C adapter does not support blocking transfer. Cannot use it!",
+ __func__);
+ return NOTIFY_DONE;
+ }
+
+
+ for (i = 0; i < 3; i++) {
+ ret = adap->algo->master_xfer_blocking(adap, &msg, 1);
+ if (ret == 0)
+ break;
+
+ printk("%s: blocking i2c transfer failed, ret =%d\n", __func__, ret);
+ if (ret != -EAGAIN) /* dont' retry, some other error */
+ break;
+
+ udelay(100);
+ printk("%s: try %d failed. Retry!\n", __func__, i);
+ }
+
+ udelay(500); /* wait for reset to assert... */
return NOTIFY_DONE;
}
@@ -253,6 +319,13 @@ static int da9063_wdt_probe(struct platform_device *pdev)
if (ret)
return ret;
+ wdt->reboot_notifier.notifier_call = da9063_wdt_reboot_notifier;
+ wdt->reboot_notifier.priority = 0; /* be the last notifier */
+ ret = register_reboot_notifier(&wdt->reboot_notifier);
+ if (ret)
+ dev_err(wdt->da9063->dev,
+ "Failed to register reboot notifier (err = %d)\n", ret);
+
wdt->restart_handler.notifier_call = da9063_wdt_restart_handler;
wdt->restart_handler.priority = 128;
ret = register_restart_handler(&wdt->restart_handler);
@@ -272,6 +345,8 @@ static int da9063_wdt_remove(struct platform_device *pdev)
/* Wait for delayed worker to finish. */
cancel_delayed_work_sync(&wdt->ping_work);
+ unregister_reboot_notifier(&wdt->reboot_notifier);
+
unregister_restart_handler(&wdt->restart_handler);
watchdog_unregister_device(&wdt->wdtdev);
--
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