[PATCH v4] i2c: designware: add a new bit check for IC_CON control

Shyam Sundar S K
2023-01-24T11:13:03Z

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>
---
v3->v4:
- cosmetic changes.
- add Reviewed-by tag.

v2->v3:
- Use regmap_read() instead of ioread32()
- Move the proposed changes to i2c_dw_probe_master() and protect the
regmap read calls with acquire/release lock calls.

v1->v2:
- Update the commit message

drivers/i2c/busses/i2c-designware-core.h | 1 +
drivers/i2c/busses/i2c-designware-master.c | 20 ++++++++++++++++++++
2 files changed, 21 insertions(+)

diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 95ebc5eaa5d1..a7ec8d5d0e72 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -37,6 +37,7 @@
#define DW_IC_CON_STOP_DET_IFADDRESSED BIT(7)
#define DW_IC_CON_TX_EMPTY_CTRL BIT(8)
#define DW_IC_CON_RX_FIFO_FULL_HLD_CTRL BIT(9)
+#define DW_IC_CON_BUS_CLEAR_CTRL BIT(11)

#define DW_IC_DATA_CMD_DAT GENMASK(7, 0)

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;
--
2.25.1