i2c: at91: implement i2c bus recovery

Implement i2c bus recovery when slaves devices might hold SDA low.
In this case re-assign SCL/SDA to gpios and issue 9 dummy clock pulses
until the slave release SDA.
Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-at91-master.c

@@ -18,11 +18,13 @@
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/err.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/platform_data/dma-atmel.h>
 #include <linux/pm_runtime.h>
@@ -478,6 +480,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
 	unsigned long time_left;
 	bool has_unre_flag = dev->pdata->has_unre_flag;
 	bool has_alt_cmd = dev->pdata->has_alt_cmd;
+	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
 
 	/*
 	 * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
@@ -637,6 +640,13 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
 		at91_twi_write(dev, AT91_TWI_CR,
 			       AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
 	}
+
+	if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
+		dev_dbg(dev->dev,
+			"SDA is down; clear bus using gpio\n");
+		i2c_recover_bus(&dev->adapter);
+	}
+
 	return ret;
 }
 
@@ -806,6 +816,70 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
 	return ret;
 }
 
+static void at91_prepare_twi_recovery(struct i2c_adapter *adap)
+{
+	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
+
+	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_gpio);
+}
+
+static void at91_unprepare_twi_recovery(struct i2c_adapter *adap)
+{
+	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
+
+	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
+}
+
+static int at91_init_twi_recovery_info(struct platform_device *pdev,
+				       struct at91_twi_dev *dev)
+{
+	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
+
+	dev->pinctrl = devm_pinctrl_get(&pdev->dev);
+	if (!dev->pinctrl || IS_ERR(dev->pinctrl)) {
+		dev_info(dev->dev, "can't get pinctrl, bus recovery not supported\n");
+		return PTR_ERR(dev->pinctrl);
+	}
+
+	dev->pinctrl_pins_default = pinctrl_lookup_state(dev->pinctrl,
+							 PINCTRL_STATE_DEFAULT);
+	dev->pinctrl_pins_gpio = pinctrl_lookup_state(dev->pinctrl,
+						      "gpio");
+	rinfo->sda_gpiod = devm_gpiod_get(&pdev->dev, "sda", GPIOD_IN);
+	if (PTR_ERR(rinfo->sda_gpiod) == -EPROBE_DEFER)
+		return -EPROBE_DEFER;
+
+	rinfo->scl_gpiod = devm_gpiod_get(&pdev->dev, "scl",
+					  GPIOD_OUT_HIGH_OPEN_DRAIN);
+	if (PTR_ERR(rinfo->scl_gpiod) == -EPROBE_DEFER)
+		return -EPROBE_DEFER;
+
+	if (IS_ERR(rinfo->sda_gpiod) ||
+	    IS_ERR(rinfo->scl_gpiod) ||
+	    IS_ERR(dev->pinctrl_pins_default) ||
+	    IS_ERR(dev->pinctrl_pins_gpio)) {
+		dev_info(&pdev->dev, "recovery information incomplete\n");
+		if (!IS_ERR(rinfo->sda_gpiod)) {
+			gpiod_put(rinfo->sda_gpiod);
+			rinfo->sda_gpiod = NULL;
+		}
+		if (!IS_ERR(rinfo->scl_gpiod)) {
+			gpiod_put(rinfo->scl_gpiod);
+			rinfo->scl_gpiod = NULL;
+		}
+		return -EINVAL;
+	}
+
+	dev_info(&pdev->dev, "using scl, sda for recovery\n");
+
+	rinfo->prepare_recovery = at91_prepare_twi_recovery;
+	rinfo->unprepare_recovery = at91_unprepare_twi_recovery;
+	rinfo->recover_bus = i2c_generic_scl_recovery;
+	dev->adapter.bus_recovery_info = rinfo;
+
+	return 0;
+}
+
 int at91_twi_probe_master(struct platform_device *pdev,
 			  u32 phy_addr, struct at91_twi_dev *dev)
 {
@@ -838,6 +912,10 @@ int at91_twi_probe_master(struct platform_device *pdev,
 						     "i2c-analog-filter");
 	at91_calc_twi_clock(dev);
 
+	rc = at91_init_twi_recovery_info(pdev, dev);
+	if (rc == -EPROBE_DEFER)
+		return rc;
+
 	dev->adapter.algo = &at91_twi_algorithm;
 	dev->adapter.quirks = &at91_twi_quirks;
 

drivers/i2c/busses/i2c-at91.h

@@ -151,6 +151,10 @@ struct at91_twi_dev {
 	u32 fifo_size;
 	struct at91_twi_dma dma;
 	bool slave_detected;
+	struct i2c_bus_recovery_info rinfo;
+	struct pinctrl *pinctrl;
+	struct pinctrl_state *pinctrl_pins_default;
+	struct pinctrl_state *pinctrl_pins_gpio;
 #ifdef CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL
 	unsigned smr;
 	struct i2c_client *slave;