[PATCH v3] i2c: cadence: Add standard bus recovery support

[Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>]

Hook up the standard GPIO/pinctrl-based recovery support.
We are doing the recovery at the beginning on a timeout.

Multiple people have contributed to the series.
Original patch from Cirag and another one from Robert.

Cc: Chirag Parekh <chiragp@xilinx.com>
Cc: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
---
 v2:
Updated the busbusy check on a timeout
v3:
Added pinctrl_get

Did unit testing and probed the scl to see the clock pulses.


 drivers/i2c/busses/i2c-cadence.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 630cfa4ddd46..c9a10d4297a9 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -10,10 +10,12 @@
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/of.h>
 #include <linux/pm_runtime.h>
+#include <linux/pinctrl/consumer.h>
 
 /* Register offsets for the I2C device. */
 #define CDNS_I2C_CR_OFFSET		0x00 /* Control Register, RW */
@@ -127,6 +129,8 @@
 #define CDNS_I2C_TIMEOUT_MAX	0xFF
 
 #define CDNS_I2C_BROKEN_HOLD_BIT	BIT(0)
+#define CDNS_I2C_POLL_US	100000
+#define CDNS_I2C_TIMEOUT_US	500000
 
 #define cdns_i2c_readreg(offset)       readl_relaxed(id->membase + offset)
 #define cdns_i2c_writereg(val, offset) writel_relaxed(val, id->membase + offset)
@@ -204,6 +208,7 @@ struct cdns_i2c {
 	struct notifier_block clk_rate_change_nb;
 	u32 quirks;
 	u32 ctrl_reg;
+	struct i2c_bus_recovery_info rinfo;
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
 	u16 ctrl_reg_diva_divb;
 	struct i2c_client *slave;
@@ -832,8 +837,14 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 #endif
 
 	/* Check if the bus is free */
-	if (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) & CDNS_I2C_SR_BA) {
+
+	ret = readl_relaxed_poll_timeout(id->membase + CDNS_I2C_SR_OFFSET,
+					 reg,
+					 !(reg & CDNS_I2C_SR_BA),
+					 CDNS_I2C_POLL_US, CDNS_I2C_TIMEOUT_US);
+	if (ret) {
 		ret = -EAGAIN;
+		i2c_recover_bus(adap);
 		goto out;
 	}
 
@@ -1242,6 +1253,12 @@ static int cdns_i2c_probe(struct platform_device *pdev)
 		id->quirks = data->quirks;
 	}
 
+	id->rinfo.pinctrl = devm_pinctrl_get(&pdev->dev);
+	if (IS_ERR(id->rinfo.pinctrl)) {
+		dev_info(&pdev->dev, "can't get pinctrl, bus recovery not supported\n");
+		return PTR_ERR(id->rinfo.pinctrl);
+	}
+
 	id->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r_mem);
 	if (IS_ERR(id->membase))
 		return PTR_ERR(id->membase);
@@ -1258,6 +1275,7 @@ static int cdns_i2c_probe(struct platform_device *pdev)
 	id->adap.retries = 3;		/* Default retry value. */
 	id->adap.algo_data = id;
 	id->adap.dev.parent = &pdev->dev;
+	id->adap.bus_recovery_info = &id->rinfo;
 	init_completion(&id->xfer_done);
 	snprintf(id->adap.name, sizeof(id->adap.name),
 		 "Cadence I2C at %08lx", (unsigned long)r_mem->start);
-- 
2.17.1