[PATCH v4] i2c: imx-lpi2c: add bus recovery feature

[carlos . song]

From: Carlos Song <carlos.song@xxxxxxx>

Add bus recovery feature for LPI2C.

Signed-off-by: Carlos Song <carlos.song@xxxxxxx>
Reviewed-by: Clark Wang <xiaoning.wang@xxxxxxx>
---
Changes for V4:
- Fix error conditions to return error value only when pinctrl defer probe.
- Add review-by.
- Clean up code.
Changes for V3:
- Modify commit log.
- Modify the return value in recovery information
  initialization function.
- Modify return value jundgment in probe.
- Simplified code comment.
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 41 ++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 678b30e90492..45ffb672fe8a 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -106,6 +106,7 @@ struct lpi2c_imx_struct {
 	unsigned int		txfifosize;
 	unsigned int		rxfifosize;
 	enum lpi2c_imx_mode	mode;
+	struct i2c_bus_recovery_info rinfo;
 };
 
 static void lpi2c_imx_intctrl(struct lpi2c_imx_struct *lpi2c_imx,
@@ -133,6 +134,8 @@ static int lpi2c_imx_bus_busy(struct lpi2c_imx_struct *lpi2c_imx)
 
 		if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {
 			dev_dbg(&lpi2c_imx->adapter.dev, "bus not work\n");
+			if (lpi2c_imx->adapter.bus_recovery_info)
+				i2c_recover_bus(&lpi2c_imx->adapter);
 			return -ETIMEDOUT;
 		}
 		schedule();
@@ -190,6 +193,8 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
 
 		if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {
 			dev_dbg(&lpi2c_imx->adapter.dev, "stop timeout\n");
+			if (lpi2c_imx->adapter.bus_recovery_info)
+				i2c_recover_bus(&lpi2c_imx->adapter);
 			break;
 		}
 		schedule();
@@ -325,6 +330,8 @@ static int lpi2c_imx_txfifo_empty(struct lpi2c_imx_struct *lpi2c_imx)
 
 		if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {
 			dev_dbg(&lpi2c_imx->adapter.dev, "txfifo empty timeout\n");
+			if (lpi2c_imx->adapter.bus_recovery_info)
+				i2c_recover_bus(&lpi2c_imx->adapter);
 			return -ETIMEDOUT;
 		}
 		schedule();
@@ -526,6 +533,34 @@ static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+/*
+ * We switch SCL and SDA to their GPIO function and do some bitbanging
+ * for bus recovery. These alternative pinmux settings can be
+ * described in the device tree by a separate pinctrl state "gpio". If
+ * this is missing this is not a big problem, the only implication is
+ * that we can't do bus recovery.
+ */
+static int lpi2c_imx_init_recovery_info(struct lpi2c_imx_struct *lpi2c_imx,
+				  struct platform_device *pdev)
+{
+	lpi2c_imx->rinfo.pinctrl = devm_pinctrl_get(&pdev->dev);
+	if (IS_ERR(lpi2c_imx->rinfo.pinctrl) || !lpi2c_imx->rinfo.pinctrl) {
+		if (PTR_ERR(lpi2c_imx->rinfo.pinctrl) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		dev_info(&pdev->dev, "bus recovery not supported\n");
+		return 0;
+	}
+
+	if (IS_ERR(pinctrl_lookup_state(lpi2c_imx->rinfo.pinctrl, "gpio"))) {
+		dev_dbg(&pdev->dev, "recovery information incomplete\n");
+		return 0;
+	}
+
+	lpi2c_imx->adapter.bus_recovery_info = &lpi2c_imx->rinfo;
+
+	return 0;
+}
+
 static u32 lpi2c_imx_func(struct i2c_adapter *adapter)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
@@ -600,6 +635,12 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
 	lpi2c_imx->txfifosize = 1 << (temp & 0x0f);
 	lpi2c_imx->rxfifosize = 1 << ((temp >> 8) & 0x0f);
 
+	/* Init optional bus recovery function */
+	ret = lpi2c_imx_init_recovery_info(lpi2c_imx, pdev);
+	/* Give it another chance if used pinctrl is not ready yet */
+	if (ret)
+		goto rpm_disable;
+
 	ret = i2c_add_adapter(&lpi2c_imx->adapter);
 	if (ret)
 		goto rpm_disable;
-- 
2.34.1