[PATCHv6 1/2] i2c: designware: introduce a custom scl recovery for SoCFPGA platforms

[Dinh Nguyen <dinguyen@kernel.org>]

The I2C pins on the SoCFPGA platforms do not go through a GPIO module,
thus cannot be recovered by the default method of by doing a GPIO access.
Only a reset of the I2C IP block can a recovery be successful, so this
change effectively resets the I2C controller, NOT any attached clients.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
---
v6: Updated commit log to emphasize this change only resets the I2C
    controller and not any attached clients.
v5: removed strayed nextline
v4: re-arrange code per Andy Shevchenko's recommendation
v3: simplify the function
    update commit message
v2: remove change to MODEL_MASK
    s/i2c_custom_scl_recovery/i2c_socfpga_scl_recovery
---
 drivers/i2c/busses/i2c-designware-core.h    |  1 +
 drivers/i2c/busses/i2c-designware-master.c  | 49 ++++++++++++++++++---
 drivers/i2c/busses/i2c-designware-platdrv.c |  1 +
 3 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 70b80e710990..7b22ec1d6a96 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -303,6 +303,7 @@ struct dw_i2c_dev {
 #define MODEL_MSCC_OCELOT	BIT(8)
 #define MODEL_BAIKAL_BT1	BIT(9)
 #define MODEL_AMD_NAVI_GPU	BIT(10)
+#define MODEL_SOCFPGA		BIT(11)
 #define MODEL_MASK		GENMASK(11, 8)
 
 /*
diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index 44a94b225ed8..fa2ea162acbd 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -813,10 +813,26 @@ static void i2c_dw_unprepare_recovery(struct i2c_adapter *adap)
 	i2c_dw_init_master(dev);
 }
 
-static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
+static int i2c_socfpga_scl_recovery(struct i2c_adapter *adap)
+{
+	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+
+	bri->prepare_recovery(adap);
+	bri->unprepare_recovery(adap);
+
+	return 0;
+}
+
+static int i2c_dw_init_socfpga_recovery_info(struct dw_i2c_dev *dev,
+					     struct i2c_bus_recovery_info *rinfo)
+{
+	rinfo->recover_bus = i2c_socfpga_scl_recovery;
+	return 1;
+}
+
+static int i2c_dw_init_generic_recovery_info(struct dw_i2c_dev *dev,
+					     struct i2c_bus_recovery_info *rinfo)
 {
-	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
-	struct i2c_adapter *adap = &dev->adapter;
 	struct gpio_desc *gpio;
 
 	gpio = devm_gpiod_get_optional(dev->dev, "scl", GPIOD_OUT_HIGH);
@@ -831,13 +847,34 @@ static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
 	rinfo->sda_gpiod = gpio;
 
 	rinfo->recover_bus = i2c_generic_scl_recovery;
-	rinfo->prepare_recovery = i2c_dw_prepare_recovery;
-	rinfo->unprepare_recovery = i2c_dw_unprepare_recovery;
-	adap->bus_recovery_info = rinfo;
 
 	dev_info(dev->dev, "running with gpio recovery mode! scl%s",
 		 rinfo->sda_gpiod ? ",sda" : "");
 
+	return 1;
+}
+
+static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
+{
+	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
+	struct i2c_adapter *adap = &dev->adapter;
+	int ret;
+
+	switch (dev->flags & MODEL_MASK) {
+	case MODEL_SOCFPGA:
+		ret = i2c_dw_init_socfpga_recovery_info(dev, rinfo);
+		break;
+	default:
+		ret = i2c_dw_init_generic_recovery_info(dev, rinfo);
+		break;
+	}
+	if (ret <= 0)
+		return ret;
+
+	rinfo->prepare_recovery = i2c_dw_prepare_recovery;
+	rinfo->unprepare_recovery = i2c_dw_unprepare_recovery;
+	adap->bus_recovery_info = rinfo;
+
 	return 0;
 }
 
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 70ade5306e45..b33e015e6732 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -153,6 +153,7 @@ static const struct of_device_id dw_i2c_of_match[] = {
 	{ .compatible = "snps,designware-i2c", },
 	{ .compatible = "mscc,ocelot-i2c", .data = (void *)MODEL_MSCC_OCELOT },
 	{ .compatible = "baikal,bt1-sys-i2c", .data = (void *)MODEL_BAIKAL_BT1 },
+	{ .compatible = "intel,socfpga-i2c", .data = (void *)MODEL_SOCFPGA },
 	{},
 };
 MODULE_DEVICE_TABLE(of, dw_i2c_of_match);
-- 
2.25.1