w1-gpio: add external pull-up enable callback

On embedded devices, sleep mode conditions can be tricky to handle,
Especially when processors tend to pull-down the w1 bus during sleep.  Bus
slaves (such as the ds2760) may interpret this as a reason for power-down
conditions and entirely switch off the device.

This patch adds a callback function pointer to let users switch on and off
the external pull-up resistor.  This lets the outside world know whether
the processor is currently actively driving the bus or not.

When this callback is not provided, the code behaviour won't change.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Acked-by: Ville Syrjala <syrjala@sci.fi>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 36 insertions, 0 deletions

diff --git a/drivers/w1/masters/w1-gpio.c b/drivers/w1/masters/w1-gpio.c
index a411702413d6..6f8866d6a905 100644
--- a/drivers/w1/masters/w1-gpio.c
+++ b/drivers/w1/masters/w1-gpio.c
@@ -74,6 +74,9 @@ static int __init w1_gpio_probe(struct platform_device *pdev)
         if (err)
                 goto free_gpio;
 
+        if (pdata->enable_external_pullup)
+                pdata->enable_external_pullup(1);
+
         platform_set_drvdata(pdev, master);
 
         return 0;
@@ -91,6 +94,9 @@ static int __exit w1_gpio_remove(struct platform_device *pdev)
         struct w1_bus_master *master = platform_get_drvdata(pdev);
         struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
 
+        if (pdata->enable_external_pullup)
+                pdata->enable_external_pullup(0);
+
         w1_remove_master_device(master);
         gpio_free(pdata->pin);
         kfree(master);
@@ -98,12 +104,41 @@ static int __exit w1_gpio_remove(struct platform_device *pdev)
         return 0;
 }
 
+#ifdef CONFIG_PM
+
+static int w1_gpio_suspend(struct platform_device *pdev, pm_message_t state)
+{
+        struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+        if (pdata->enable_external_pullup)
+                pdata->enable_external_pullup(0);
+
+        return 0;
+}
+
+static int w1_gpio_resume(struct platform_device *pdev)
+{
+        struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+        if (pdata->enable_external_pullup)
+                pdata->enable_external_pullup(1);
+
+        return 0;
+}
+
+#else
+#define w1_gpio_suspend NULL
+#define w1_gpio_resume  NULL
+#endif
+
 static struct platform_driver w1_gpio_driver = {
         .driver = {
                 .name   = "w1-gpio",
                 .owner  = THIS_MODULE,
         },
         .remove = __exit_p(w1_gpio_remove),
+        .suspend = w1_gpio_suspend,
+        .resume = w1_gpio_resume,
 };
 
 static int __init w1_gpio_init(void)
diff --git a/include/linux/w1-gpio.h b/include/linux/w1-gpio.h
index 9797fec7748a..3adeff82212f 100644
--- a/include/linux/w1-gpio.h
+++ b/include/linux/w1-gpio.h
@@ -18,6 +18,7 @@
 struct w1_gpio_platform_data {
         unsigned int pin;
         unsigned int is_open_drain:1;
+        void (*enable_external_pullup)(int enable);
 };
 
 #endif /* _LINUX_W1_GPIO_H */