i2c: designware: add a new bit check for IC_CON control

On some AMD platforms, based on the new designware datasheet,
BIOS sets the BIT(11) within the IC_CON register to advertise
the "bus clear feature capability".

AMD/Designware datasheet says:

Bit(11) BUS_CLEAR_FEATURE_CTRL. Read-write,Volatile. Reset: 0.
Description: In Master mode:
- 1'b1: Bus Clear Feature is enabled.
- 1'b0: Bus Clear Feature is Disabled.
In Slave mode, this register bit is not applicable.

On AMD platform designs:
1. BIOS programs the BUS_CLEAR_FEATURE_CTRL and enables the detection
of SCL/SDA stuck low.
2. Whenever the stuck low is detected, the SMU FW shall do the bus
recovery procedure.

Currently, the way in which the "master_cfg" is built in the driver, it
overrides the BUS_CLEAR_FEATURE_CTRL advertised by BIOS and the SMU FW
cannot initiate the bus recovery if the stuck low is detected.

Hence add a check in i2c_dw_probe_master() that if the BIOS
advertises the bus clear feature, let driver not ignore it and
adapt accordingly.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index 45f569155bfe..3be7581ee3fb 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -865,6 +865,7 @@ int i2c_dw_probe_master(struct dw_i2c_dev *dev)
 {
 	struct i2c_adapter *adap = &dev->adapter;
 	unsigned long irq_flags;
+	unsigned int ic_con;
 	int ret;
 
 	init_completion(&dev->cmd_complete);
@@ -884,6 +885,25 @@ int i2c_dw_probe_master(struct dw_i2c_dev *dev)
 	if (ret)
 		return ret;
 
+	/* Lock the bus for accessing DW_IC_CON */
+	ret = i2c_dw_acquire_lock(dev);
+	if (ret)
+		return ret;
+
+	/*
+	 * On AMD platforms BIOS advertises the bus clear feature
+	 * and enables the SCL/SDA stuck low. SMU FW does the
+	 * bus recovery process. Driver should not ignore this BIOS
+	 * advertisement of bus clear feature.
+	 */
+	ret = regmap_read(dev->map, DW_IC_CON, &ic_con);
+	i2c_dw_release_lock(dev);
+	if (ret)
+		return ret;
+
+	if (ic_con & DW_IC_CON_BUS_CLEAR_CTRL)
+		dev->master_cfg |= DW_IC_CON_BUS_CLEAR_CTRL;
+
 	ret = dev->init(dev);
 	if (ret)
 		return ret;