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

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

[Shyam Sundar S K]

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

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

[Jarkko Nikula]

On 1/24/23 13:11, Shyam Sundar S K wrote:
> 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>

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

[Wolfram Sang]

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On Tue, Jan 24, 2023 at 04:41:27PM +0530, Shyam Sundar S K wrote:
> 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>

Applied to for-next, thanks!


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