i2c-imx: add gpio recovery functionality

If the I2C is disturbed by other signals sometimes the i2c-imx bus gets stuck
with SDA being low.
This adds a recovery function to the bus driver.

When e.g. a device driver detects a stuck bus
int i2c_recover_bus(struct i2c_adapter *adap)
can be called to try to recover the bus.

(cherry picked from commit 88731dc0e8b6ba244e097b412b302acf3b9cc889)

Conflicts:
	arch/arm/boot/dts/imx6qdl-apalis.dtsi
	drivers/i2c/busses/i2c-imx.c

1 files changed, 73 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 3ed8e47785fc..bae984eebe08 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -52,6 +52,7 @@
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/of_gpio.h>
 #include <linux/platform_data/i2c-imx.h>
 
 /** Defines ********************************************************************
@@ -610,16 +611,71 @@ static struct i2c_algorithm i2c_imx_algo = {
 	.functionality	= i2c_imx_func,
 };
 
+static int of_i2c_imx_get_pins(struct device_node *np,
+				unsigned int *sda_pin, unsigned int *scl_pin)
+{
+	if (of_gpio_count(np) < 2)
+		return -ENODEV;
+
+	*sda_pin = of_get_gpio(np, 0);
+	*scl_pin = of_get_gpio(np, 1);
+	if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) {
+		pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
+		       np->full_name, *sda_pin, *scl_pin);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+/* i2c bus recovery routines */
+static int get_scl_gpio_value(struct i2c_adapter *adap)
+{
+	return gpio_get_value(adap->bus_recovery_info->scl_gpio);
+}
+
+static void set_scl_gpio_value(struct i2c_adapter *adap, int val)
+{
+	gpio_set_value(adap->bus_recovery_info->scl_gpio, val);
+}
+
+static int get_sda_gpio_value(struct i2c_adapter *adap)
+{
+	return gpio_get_value(adap->bus_recovery_info->sda_gpio);
+}
+
+int i2c_imx_recover_bus(struct i2c_adapter *adap)
+{
+	/* i2c_imx_(un)prepare_recovery can not be used for pinmuxing, as we
+	 *  need the data from struct i2c_adapter */
+	int ret;
+
+	if(!devm_pinctrl_get_select(adap->dev.parent, "recovery")) {
+		dev_err(adap->dev.parent, "%s> switching to 'recover' pinmux failed\n", __func__);
+	}
+
+	ret = i2c_generic_gpio_recovery(adap);
+
+	if(!devm_pinctrl_get_select_default(adap->dev.parent)) {
+		dev_err(adap->dev.parent, "<%s> switching from 'recover' to 'default' pinmux failed\n", __func__);
+	}
+
+	return ret;
+}
+
 static int i2c_imx_probe(struct platform_device *pdev)
 {
 	const struct of_device_id *of_id = of_match_device(i2c_imx_dt_ids,
 							   &pdev->dev);
 	struct imx_i2c_struct *i2c_imx;
+	struct i2c_bus_recovery_info *bri;
 	struct resource *res;
 	struct imxi2c_platform_data *pdata = dev_get_platdata(&pdev->dev);
 	void __iomem *base;
 	int irq, ret;
 	u32 bitrate;
+	int sda_gpio = -1;
+	int scl_gpio = -1;
 
 	dev_dbg(&pdev->dev, "<%s>\n", __func__);
 
@@ -682,6 +738,23 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	/* Set up adapter data */
 	i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);
 
+	/* Set up adapter recovery info */
+	if (of_i2c_imx_get_pins(pdev->dev.of_node, &sda_gpio, &scl_gpio) >= 0) {
+		bri = devm_kzalloc(&pdev->dev,
+			sizeof(struct i2c_bus_recovery_info), GFP_KERNEL);
+		if (!bri)
+			dev_info(&pdev->dev, "can't allocate i2c recovery struct, recovery will not work\n");
+		else {
+			bri->recover_bus = i2c_imx_recover_bus;
+			bri->get_sda = get_sda_gpio_value;
+			bri->get_scl = get_scl_gpio_value;
+			bri->set_scl = set_scl_gpio_value;
+			bri->sda_gpio = sda_gpio;
+			bri->scl_gpio = scl_gpio;
+			i2c_imx->adapter.bus_recovery_info = bri;
+		}
+	}
+
 	/* Set up clock divider */
 	bitrate = IMX_I2C_BIT_RATE;
 	ret = of_property_read_u32(pdev->dev.of_node,