[PATCH v4 0/6] i2c: npcm: read/write operation, checkpatch

[PATCH v4 0/6] i2c: npcm: read/write operation, checkpatch

[warp5tw]

From: Tyrone Ting <kfting@nuvoton.com>

This patchset includes the following fixes:

- Enable the target functionality in the interrupt handling routine 
  when the i2c transfer is about to finish.
- Correct the read/write operation procedure.
- Introduce a software flag to handle the bus error (BER) condition
  which is not caused by the i2c transfer.
- Modify timeout calculation.
- Assign the client address earlier logically.
- Use an i2c frequency table for the frequency parameters assignment.
- Coding style fix.

The NPCM I2C driver is tested on NPCM750 and NPCM845 evaluation boards.

Addressed comments from:
- Andy Shevchenko : https://lore.kernel.org/linux-i2c/ZuQUfCK7d7DuR9eH
  @smile.fi.intel.com/
- Andy Shevchenko : https://lore.kernel.org/linux-i2c/ZuQU2iIZwW4mAumo
  @smile.fi.intel.com/
- Andy Shevchenko : https://lore.kernel.org/linux-i2c/ZuQWYabomv_xyYyj
  @smile.fi.intel.com/ 

Changes since version 3:
- Remove "Bug fixes" in the cover letter title.
- Modify the term "function" to "func()" in the commit message and
  code comments.
- Correct the coding style.

Changes since version 2:
- Add more explanations in the commit message and code modification.
- Use lower character names for declarations.
- Remove Fixes tags in commits which are not to fix bugs.

Changes since version 1:
- Restore the npcm_i2caddr array length to fix the smatch warning.
- Remove unused variables.
- Handle the condition where scl_table_cnt reaches to the maximum value.
- Fix the checkpatch warning.

Charles Boyer (1):
  i2c: npcm: Enable slave in eob interrupt

Tyrone Ting (5):
  i2c: npcm: correct the read/write operation procedure
  i2c: npcm: use a software flag to indicate a BER condition
  i2c: npcm: Modify timeout evaluation mechanism
  i2c: npcm: Modify the client address assignment
  i2c: npcm: use i2c frequency table

 drivers/i2c/busses/i2c-npcm7xx.c | 425 +++++++++++++++++++++++--------
 1 file changed, 323 insertions(+), 102 deletions(-)


base-commit: f56f4ba2fc1dbefd3242946f2fad35338a60e3bc
-- 
2.34.1

[PATCH v4 1/6] i2c: npcm: correct the read/write operation procedure

[warp5tw]

From: Tyrone Ting <kfting@nuvoton.com>

From: Tyrone Ting <kfting@nuvoton.com>

Originally the driver uses the XMIT bit in SMBnST register to decide
the upcoming i2c transaction. If XMIT bit is 1, then it will be an i2c
write operation. If it's 0, then a read operation will be executed.

In slave mode the XMIT bit can simply be used directly to set the state.
XMIT bit can be used as an indication to the current state of the state
machine during slave operation. (meaning XMIT = 1 during writing and
XMIT = 0 during reading).

In master operation XMIT is valid only if there are no bus errors.
For example: in a multi master where the same module is switching from
master to slave at runtime, and there are collisions, the XMIT bit
cannot be trusted.

However the maser already "knows" what the bus state is, so this bit
is not needed and the driver can just track what it is currently doing.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index bbcb4d6668ce..2b76dbfba438 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -1628,13 +1628,10 @@ static void npcm_i2c_irq_handle_sda(struct npcm_i2c *bus, u8 i2cst)
 			npcm_i2c_wr_byte(bus, bus->dest_addr | BIT(0));
 	/* SDA interrupt, after start\restart */
 	} else {
-		if (NPCM_I2CST_XMIT & i2cst) {
-			bus->operation = I2C_WRITE_OPER;
+		if (bus->operation == I2C_WRITE_OPER)
 			npcm_i2c_irq_master_handler_write(bus);
-		} else {
-			bus->operation = I2C_READ_OPER;
+		else if (bus->operation == I2C_READ_OPER)
 			npcm_i2c_irq_master_handler_read(bus);
-		}
 	}
 }
 
-- 
2.34.1

[PATCH v4 2/6] i2c: npcm: use a software flag to indicate a BER condition

[warp5tw]

From: Tyrone Ting <kfting@nuvoton.com>

From: Tyrone Ting <kfting@nuvoton.com>

If not clearing the BB (bus busy) condition in the BER (bus error)
interrupt, the driver causes a timeout and hence the i2c core
doesn't do the i2c transfer retry but returns the driver's return
value to the upper layer instead.

Clear the BB condition in the BER interrupt and a software flag is
used. The driver does an i2c recovery without causing the timeout
if the flag is set.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 2b76dbfba438..2d034503d8bc 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -334,6 +334,7 @@ struct npcm_i2c {
 	u64 nack_cnt;
 	u64 timeout_cnt;
 	u64 tx_complete_cnt;
+	bool ber_state;
 };
 
 static inline void npcm_i2c_select_bank(struct npcm_i2c *bus,
@@ -1521,6 +1522,7 @@ static void npcm_i2c_irq_handle_ber(struct npcm_i2c *bus)
 	if (npcm_i2c_is_master(bus)) {
 		npcm_i2c_master_abort(bus);
 	} else {
+		bus->ber_state = true;
 		npcm_i2c_clear_master_status(bus);
 
 		/* Clear BB (BUS BUSY) bit */
@@ -1699,6 +1701,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
 		dev_dbg(bus->dev, "bus%d-0x%x recovery skipped, bus not stuck",
 			bus->num, bus->dest_addr);
 		npcm_i2c_reset(bus);
+		bus->ber_state = false;
 		return 0;
 	}
 
@@ -1763,6 +1766,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
 		if (bus->rec_succ_cnt < ULLONG_MAX)
 			bus->rec_succ_cnt++;
 	}
+	bus->ber_state = false;
 	return status;
 }
 
@@ -2158,7 +2162,7 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 
 	} while (time_is_after_jiffies(time_left) && bus_busy);
 
-	if (bus_busy) {
+	if (bus_busy || bus->ber_state) {
 		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
 		npcm_i2c_reset(bus);
 		i2c_recover_bus(adap);
-- 
2.34.1

[PATCH v4 3/6] i2c: npcm: Modify timeout evaluation mechanism

[warp5tw]

From: Tyrone Ting <kfting@nuvoton.com>

From: Tyrone Ting <kfting@nuvoton.com>

The users want to connect a lot of masters on the same bus.
This timeout is used to determine the time it takes to take bus ownership.
The transactions are very long, so waiting 35ms is not enough.

Increase the timeout and treat it as the total timeout, including retries.
The total timeout is 2 seconds now.

The i2c core layer will have chances to retry to call the i2c driver
transfer function if the i2c driver reports that the bus is busy and
returns EAGAIN.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 2d034503d8bc..68f3d47323ab 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -2132,19 +2132,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 		}
 	}
 
-	/*
-	 * Adaptive TimeOut: estimated time in usec + 100% margin:
-	 * 2: double the timeout for clock stretching case
-	 * 9: bits per transaction (including the ack/nack)
-	 */
-	timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
-	timeout = max_t(unsigned long, bus->adap.timeout, usecs_to_jiffies(timeout_usec));
 	if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
 		dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
 		return -EINVAL;
 	}
 
-	time_left = jiffies + timeout + 1;
+	time_left = jiffies + bus->adap.timeout / bus->adap.retries + 1;
 	do {
 		/*
 		 * we must clear slave address immediately when the bus is not
@@ -2183,6 +2176,14 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	if (npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
 				       write_data, read_data, read_PEC,
 				       read_block)) {
+		/*
+		 * Adaptive TimeOut: estimated time in usec + 100% margin:
+		 * 2: double the timeout for clock stretching case
+		 * 9: bits per transaction (including the ack/nack)
+		 */
+		timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
+		timeout = max_t(unsigned long, bus->adap.timeout / bus->adap.retries,
+				usecs_to_jiffies(timeout_usec));
 		time_left = wait_for_completion_timeout(&bus->cmd_complete,
 							timeout);
 
@@ -2308,7 +2309,7 @@ static int npcm_i2c_probe_bus(struct platform_device *pdev)
 	adap = &bus->adap;
 	adap->owner = THIS_MODULE;
 	adap->retries = 3;
-	adap->timeout = msecs_to_jiffies(35);
+	adap->timeout = 2 * HZ;
 	adap->algo = &npcm_i2c_algo;
 	adap->quirks = &npcm_i2c_quirks;
 	adap->algo_data = bus;
-- 
2.34.1

[PATCH v4 4/6] i2c: npcm: Modify the client address assignment

[warp5tw]

From: Tyrone Ting <kfting@nuvoton.com>

From: Tyrone Ting <kfting@nuvoton.com>

Store the client address earlier since it might get called in
the i2c_recover_bus logic flow at the early stage of the func()
npcm_i2c_master_xfer.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 68f3d47323ab..248835220c86 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -2155,6 +2155,18 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 
 	} while (time_is_after_jiffies(time_left) && bus_busy);
 
+	/*
+	 * Previously, the address was stored w/o left-shift by one bit and
+	 * with that shift in the following call to npcm_i2c_master_start_xmit.
+	 *
+	 * Since there are cases that the i2c_recover_bus gets called at the
+	 * early stage of the func() npcm_i2c_master_xfer, the address is
+	 * stored with the shift and used in the i2c_recover_bus call.
+	 *
+	 * The address is stored from bit 1 to bit 7 in the register for
+	 * sending the i2c address later so it's left-shifted by 1 bit.
+	 */
+	bus->dest_addr = slave_addr << 1;
 	if (bus_busy || bus->ber_state) {
 		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
 		npcm_i2c_reset(bus);
@@ -2163,7 +2175,6 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	}
 
 	npcm_i2c_init_params(bus);
-	bus->dest_addr = slave_addr;
 	bus->msgs = msgs;
 	bus->msgs_num = num;
 	bus->cmd_err = 0;
-- 
2.34.1

[PATCH v4 5/6] i2c: npcm: use i2c frequency table

[warp5tw]

From: Tyrone Ting <kfting@nuvoton.com>

From: Tyrone Ting <kfting@nuvoton.com>

Modify i2c frequency from table parameters
for NPCM i2c modules.

Supported frequencies are:

1. 100KHz
2. 400KHz
3. 1MHz

The original equations were tested on a variety of chips and base clocks.
Since we added devices that use higher frequencies of the module we
saw that there is a mismatch between the equation and the actual
results on the bus itself, measured on scope.

Meanwhile, the equations were not accurate to begin with.
They are an approximation of the ideal value. The ideal value is
calculated per frequency of the core module.

So instead of using the equations we did an optimization per module
frequency, verified on a device.

Most of the work was focused on the rise time of the SCL and SDA,
which depends on external load of the bus and PU.

Different PCB designs, or specifically to this case: the number
and type of targets on the bus, impact the required values for
the timing registers.

Users can recalculate the numbers for each bus and get an even better
optimization, but our users chose not to.

We manually picked values per frequency that match the entire valid
range of targets (from 1 to max number). Then we check against the
AMR described in SMB spec and make sure that none of the values
is exceeding.

This process was led by the chip architect and included a lot of testing.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 374 ++++++++++++++++++++++++-------
 1 file changed, 288 insertions(+), 86 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 248835220c86..9d533873e477 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -263,6 +263,265 @@ static const int npcm_i2caddr[I2C_NUM_OWN_ADDR] = {
 #define I2C_FREQ_MIN_HZ			10000
 #define I2C_FREQ_MAX_HZ			I2C_MAX_FAST_MODE_PLUS_FREQ
 
+struct smb_timing_t {
+	u32 core_clk;
+	u8 hldt;
+	u8 dbcnt;
+	u16 sclfrq;
+	u8 scllt;
+	u8 sclht;
+	bool fast_mode;
+};
+
+static struct smb_timing_t smb_timing_100khz[] = {
+	{
+		.core_clk = 100000000, .hldt = 0x2A, .dbcnt = 0x4,
+		.sclfrq = 0xFB, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 62500000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x9D, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 50000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x7E, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 48000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x79, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 40000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x65, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 30000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x4C, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 29000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x49, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 26000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x42, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 25000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x3F, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 24000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x3D, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 20000000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x33, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 16180000, .hldt = 0x2A, .dbcnt = 0x1,
+		.sclfrq = 0x29, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 15000000, .hldt = 0x23, .dbcnt = 0x1,
+		.sclfrq = 0x26, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 13000000, .hldt = 0x1D, .dbcnt = 0x1,
+		.sclfrq = 0x21, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 12000000, .hldt = 0x1B, .dbcnt = 0x1,
+		.sclfrq = 0x1F, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 10000000, .hldt = 0x18, .dbcnt = 0x1,
+		.sclfrq = 0x1A, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 9000000, .hldt = 0x16, .dbcnt = 0x1,
+		.sclfrq = 0x17, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 8090000, .hldt = 0x14, .dbcnt = 0x1,
+		.sclfrq = 0x15, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 7500000, .hldt = 0x7, .dbcnt = 0x1,
+		.sclfrq = 0x13, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 6500000, .hldt = 0xE, .dbcnt = 0x1,
+		.sclfrq = 0x11, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+	{
+		.core_clk = 4000000, .hldt = 0x9, .dbcnt = 0x1,
+		.sclfrq = 0xB, .scllt = 0x0, .sclht = 0x0,
+		.fast_mode = false,
+	},
+};
+
+static struct smb_timing_t smb_timing_400khz[] = {
+	{
+		.core_clk = 100000000, .hldt = 0x2A, .dbcnt = 0x3,
+		.sclfrq = 0x0, .scllt = 0x47, .sclht = 0x35,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 62500000, .hldt = 0x2A, .dbcnt = 0x2,
+		.sclfrq = 0x0, .scllt = 0x2C, .sclht = 0x22,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 50000000, .hldt = 0x21, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x24, .sclht = 0x1B,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 48000000, .hldt = 0x1E, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x24, .sclht = 0x19,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 40000000, .hldt = 0x1B, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x1E, .sclht = 0x14,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 33000000, .hldt = 0x15, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x19, .sclht = 0x11,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 30000000, .hldt = 0x15, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x19, .sclht = 0xD,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 29000000, .hldt = 0x11, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x15, .sclht = 0x10,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 26000000, .hldt = 0x10, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x13, .sclht = 0xE,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 25000000, .hldt = 0xF, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x13, .sclht = 0xD,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 24000000, .hldt = 0xD, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x12, .sclht = 0xD,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 20000000, .hldt = 0xB, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0xF, .sclht = 0xA,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 16180000, .hldt = 0xA, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0xC, .sclht = 0x9,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 15000000, .hldt = 0x9, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0xB, .sclht = 0x8,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 13000000, .hldt = 0x7, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0xA, .sclht = 0x7,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 12000000, .hldt = 0x7, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0xA, .sclht = 0x6,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 10000000, .hldt = 0x6, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x8, .sclht = 0x5,
+		.fast_mode = true,
+	},
+};
+
+static struct smb_timing_t smb_timing_1000khz[] = {
+	{
+		.core_clk = 100000000, .hldt = 0x15, .dbcnt = 0x4,
+		.sclfrq = 0x0, .scllt = 0x1C, .sclht = 0x15,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 62500000, .hldt = 0xF, .dbcnt = 0x3,
+		.sclfrq = 0x0, .scllt = 0x11, .sclht = 0xE,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 50000000, .hldt = 0xA, .dbcnt = 0x2,
+		.sclfrq = 0x0, .scllt = 0xE, .sclht = 0xB,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 48000000, .hldt = 0x9, .dbcnt = 0x2,
+		.sclfrq = 0x0, .scllt = 0xD, .sclht = 0xB,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 41000000, .hldt = 0x9, .dbcnt = 0x2,
+		.sclfrq = 0x0, .scllt = 0xC, .sclht = 0x9,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 40000000, .hldt = 0x8, .dbcnt = 0x2,
+		.sclfrq = 0x0, .scllt = 0xB, .sclht = 0x9,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 33000000, .hldt = 0x7, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0xA, .sclht = 0x7,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 25000000, .hldt = 0x4, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x7, .sclht = 0x6,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 24000000, .hldt = 0x7, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x8, .sclht = 0x5,
+		.fast_mode = true,
+	},
+	{
+		.core_clk = 20000000, .hldt = 0x4, .dbcnt = 0x1,
+		.sclfrq = 0x0, .scllt = 0x6, .sclht = 0x4,
+		.fast_mode = true,
+	},
+};
+
 struct npcm_i2c_data {
 	u8 fifo_size;
 	u32 segctl_init_val;
@@ -1805,102 +2064,45 @@ static void npcm_i2c_recovery_init(struct i2c_adapter *_adap)
  */
 static int npcm_i2c_init_clk(struct npcm_i2c *bus, u32 bus_freq_hz)
 {
-	u32  k1 = 0;
-	u32  k2 = 0;
-	u8   dbnct = 0;
-	u32  sclfrq = 0;
-	u8   hldt = 7;
+	struct  smb_timing_t *smb_timing;
+	u8   scl_table_cnt = 0, table_size = 0;
 	u8   fast_mode = 0;
-	u32  src_clk_khz;
-	u32  bus_freq_khz;
 
-	src_clk_khz = bus->apb_clk / 1000;
-	bus_freq_khz = bus_freq_hz / 1000;
 	bus->bus_freq = bus_freq_hz;
 
-	/* 100KHz and below: */
-	if (bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ) {
-		sclfrq = src_clk_khz / (bus_freq_khz * 4);
-
-		if (sclfrq < SCLFRQ_MIN || sclfrq > SCLFRQ_MAX)
-			return -EDOM;
-
-		if (src_clk_khz >= 40000)
-			hldt = 17;
-		else if (src_clk_khz >= 12500)
-			hldt = 15;
-		else
-			hldt = 7;
-	}
-
-	/* 400KHz: */
-	else if (bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ) {
-		sclfrq = 0;
+	switch (bus_freq_hz) {
+	case I2C_MAX_STANDARD_MODE_FREQ:
+		smb_timing = smb_timing_100khz;
+		table_size = ARRAY_SIZE(smb_timing_100khz);
+		break;
+	case I2C_MAX_FAST_MODE_FREQ:
+		smb_timing = smb_timing_400khz;
+		table_size = ARRAY_SIZE(smb_timing_400khz);
 		fast_mode = I2CCTL3_400K_MODE;
-
-		if (src_clk_khz < 7500)
-			/* 400KHZ cannot be supported for core clock < 7.5MHz */
-			return -EDOM;
-
-		else if (src_clk_khz >= 50000) {
-			k1 = 80;
-			k2 = 48;
-			hldt = 12;
-			dbnct = 7;
-		}
-
-		/* Master or Slave with frequency > 25MHz */
-		else if (src_clk_khz > 25000) {
-			hldt = clk_coef(src_clk_khz, 300) + 7;
-			k1 = clk_coef(src_clk_khz, 1600);
-			k2 = clk_coef(src_clk_khz, 900);
-		}
-	}
-
-	/* 1MHz: */
-	else if (bus_freq_hz <= I2C_MAX_FAST_MODE_PLUS_FREQ) {
-		sclfrq = 0;
+		break;
+	case I2C_MAX_FAST_MODE_PLUS_FREQ:
+		smb_timing = smb_timing_1000khz;
+		table_size = ARRAY_SIZE(smb_timing_1000khz);
 		fast_mode = I2CCTL3_400K_MODE;
-
-		/* 1MHZ cannot be supported for core clock < 24 MHz */
-		if (src_clk_khz < 24000)
-			return -EDOM;
-
-		k1 = clk_coef(src_clk_khz, 620);
-		k2 = clk_coef(src_clk_khz, 380);
-
-		/* Core clk > 40 MHz */
-		if (src_clk_khz > 40000) {
-			/*
-			 * Set HLDT:
-			 * SDA hold time:  (HLDT-7) * T(CLK) >= 120
-			 * HLDT = 120/T(CLK) + 7 = 120 * FREQ(CLK) + 7
-			 */
-			hldt = clk_coef(src_clk_khz, 120) + 7;
-		} else {
-			hldt = 7;
-			dbnct = 2;
-		}
+		break;
+	default:
+		return -EINVAL;
 	}
 
-	/* Frequency larger than 1 MHz is not supported */
-	else
-		return -EINVAL;
+	for (scl_table_cnt = 0; scl_table_cnt < table_size; scl_table_cnt++)
+		if (bus->apb_clk >= smb_timing[scl_table_cnt].core_clk)
+			break;
 
-	if (bus_freq_hz >= I2C_MAX_FAST_MODE_FREQ) {
-		k1 = round_up(k1, 2);
-		k2 = round_up(k2 + 1, 2);
-		if (k1 < SCLFRQ_MIN || k1 > SCLFRQ_MAX ||
-		    k2 < SCLFRQ_MIN || k2 > SCLFRQ_MAX)
-			return -EDOM;
-	}
+	if (scl_table_cnt == table_size)
+		return -EINVAL;
 
 	/* write sclfrq value. bits [6:0] are in I2CCTL2 reg */
-	iowrite8(FIELD_PREP(I2CCTL2_SCLFRQ6_0, sclfrq & 0x7F),
+	iowrite8(FIELD_PREP(I2CCTL2_SCLFRQ6_0, smb_timing[scl_table_cnt].sclfrq & 0x7F),
 		 bus->reg + NPCM_I2CCTL2);
 
 	/* bits [8:7] are in I2CCTL3 reg */
-	iowrite8(fast_mode | FIELD_PREP(I2CCTL3_SCLFRQ8_7, (sclfrq >> 7) & 0x3),
+	iowrite8(FIELD_PREP(I2CCTL3_SCLFRQ8_7, (smb_timing[scl_table_cnt].sclfrq >> 7) & 0x3) |
+		 fast_mode,
 		 bus->reg + NPCM_I2CCTL3);
 
 	/* Select Bank 0 to access NPCM_I2CCTL4/NPCM_I2CCTL5 */
@@ -1912,13 +2114,13 @@ static int npcm_i2c_init_clk(struct npcm_i2c *bus, u32 bus_freq_hz)
 		 * k1 = 2 * SCLLT7-0 -> Low Time  = k1 / 2
 		 * k2 = 2 * SCLLT7-0 -> High Time = k2 / 2
 		 */
-		iowrite8(k1 / 2, bus->reg + NPCM_I2CSCLLT);
-		iowrite8(k2 / 2, bus->reg + NPCM_I2CSCLHT);
+		iowrite8(smb_timing[scl_table_cnt].scllt, bus->reg + NPCM_I2CSCLLT);
+		iowrite8(smb_timing[scl_table_cnt].sclht, bus->reg + NPCM_I2CSCLHT);
 
-		iowrite8(dbnct, bus->reg + NPCM_I2CCTL5);
+		iowrite8(smb_timing[scl_table_cnt].dbcnt, bus->reg + NPCM_I2CCTL5);
 	}
 
-	iowrite8(hldt, bus->reg + NPCM_I2CCTL4);
+	iowrite8(smb_timing[scl_table_cnt].hldt, bus->reg + NPCM_I2CCTL4);
 
 	/* Return to Bank 1, and stay there by default: */
 	npcm_i2c_select_bank(bus, I2C_BANK_1);
-- 
2.34.1

[PATCH v4 6/6] i2c: npcm: Enable slave in eob interrupt

[warp5tw]

From: Charles Boyer <Charles.Boyer@fii-usa.com>

Nuvoton slave enable was in user space API call master_xfer, so it is
subject to delays from the OS scheduler. If the BMC is not enabled for
slave mode in time for master to send response, then it will NAK the
address match. Then the PLDM request timeout occurs.

If the slave enable is moved to the EOB interrupt service routine, then
the BMC can be ready in slave mode by the time it needs to receive a
response.

Signed-off-by: Charles Boyer <Charles.Boyer@fii-usa.com>
Signed-off-by: Vivekanand Veeracholan <vveerach@google.com>
Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 9d533873e477..aa3310afbf6d 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -1925,6 +1925,12 @@ static int npcm_i2c_int_master_handler(struct npcm_i2c *bus)
 	    (FIELD_GET(NPCM_I2CCST3_EO_BUSY,
 		       ioread8(bus->reg + NPCM_I2CCST3)))) {
 		npcm_i2c_irq_handle_eob(bus);
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+		/* reenable slave if it was enabled */
+		if (bus->slave)
+			iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,
+				 bus->reg + NPCM_I2CADDR1);
+#endif
 		return 0;
 	}
 
-- 
2.34.1

Re: [PATCH v4 1/6] i2c: npcm: correct the read/write operation procedure

[Andy Shevchenko]

On Fri, Sep 20, 2024 at 06:18:15PM +0800, warp5tw@gmail.com wrote:
> From: Tyrone Ting <kfting@nuvoton.com>
> 
> From: Tyrone Ting <kfting@nuvoton.com>

Something wrong with your email setup. This patch may not be applied in this form.

But before (re-)sending, wait for others to comment (up to 1 week).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 4/6] i2c: npcm: Modify the client address assignment

[Andy Shevchenko]

On Fri, Sep 20, 2024 at 06:18:18PM +0800, warp5tw@gmail.com wrote:
> From: Tyrone Ting <kfting@nuvoton.com>
> 
> From: Tyrone Ting <kfting@nuvoton.com>

It seems all your mails have an issue.

> Store the client address earlier since it might get called in
> the i2c_recover_bus logic flow at the early stage of the func()
> npcm_i2c_master_xfer.

You got my comment really wrong.

func() in my example was to refer to _a_ function mentioned in the text.
And IIRC I even posted the example, like: i2c_recover_bus().

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 1/6] i2c: npcm: correct the read/write operation procedure

[Tyrone Ting]

Hi Andy:

Thank you for your feedback.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年9月20日 週五 下午10:30寫道：
>
> On Fri, Sep 20, 2024 at 06:18:15PM +0800, warp5tw@gmail.com wrote:
> > From: Tyrone Ting <kfting@nuvoton.com>
> >
> > From: Tyrone Ting <kfting@nuvoton.com>
>
> Something wrong with your email setup. This patch may not be applied in this form.
>
> But before (re-)sending, wait for others to comment (up to 1 week).
>

I'll remove the "--from" parameter to git send-email command in next patch set.

> --
> With Best Regards,
> Andy Shevchenko
>
>

Thank you.

Regards,
Tyrone

Re: [PATCH v4 4/6] i2c: npcm: Modify the client address assignment

[Tyrone Ting]

Hi Andy:

Thank you for your feedback.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年9月20日 週五 下午10:33寫道：
>
> On Fri, Sep 20, 2024 at 06:18:18PM +0800, warp5tw@gmail.com wrote:
> > From: Tyrone Ting <kfting@nuvoton.com>
> >
> > From: Tyrone Ting <kfting@nuvoton.com>
>
> It seems all your mails have an issue.
>

Acked in the previous email.

> > Store the client address earlier since it might get called in
> > the i2c_recover_bus logic flow at the early stage of the func()
> > npcm_i2c_master_xfer.
>
> You got my comment really wrong.
>
> func() in my example was to refer to _a_ function mentioned in the text.
> And IIRC I even posted the example, like: i2c_recover_bus().
>

So the commit message in next patch set would be like:
Store the client address earlier since it might get called in
the i2c_recover_bus() logic flow at the early stage of
npcm_i2c_master_xfer().

The code comment would be like:
Previously, the address was stored w/o left-shift by one bit and
with that shift in the following call to npcm_i2c_master_start_xmit().

Since there are cases that the i2c_recover_bus() gets called at the
early stage of npcm_i2c_master_xfer(), the address is
stored with the shift and used in the i2c_recover_bus call().


> --
> With Best Regards,
> Andy Shevchenko
>
>

Have a nice day.

Regards,
Tyrone

Re: [PATCH v4 4/6] i2c: npcm: Modify the client address assignment

[Andy Shevchenko]

On Mon, Sep 23, 2024 at 09:59:31AM +0800, Tyrone Ting wrote:
> Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年9月20日 週五 下午10:33寫道：
> > On Fri, Sep 20, 2024 at 06:18:18PM +0800, warp5tw@gmail.com wrote:

...

> > > Store the client address earlier since it might get called in
> > > the i2c_recover_bus logic flow at the early stage of the func()
> > > npcm_i2c_master_xfer.
> >
> > You got my comment really wrong.
> >
> > func() in my example was to refer to _a_ function mentioned in the text.
> > And IIRC I even posted the example, like: i2c_recover_bus().
> 
> So the commit message in next patch set would be like:

Yes.

> Store the client address earlier since it might get called in
> the i2c_recover_bus() logic flow at the early stage of
> npcm_i2c_master_xfer().
> 
> The code comment would be like:

Yes!

> Previously, the address was stored w/o left-shift by one bit and
> with that shift in the following call to npcm_i2c_master_start_xmit().
> 
> Since there are cases that the i2c_recover_bus() gets called at the
> early stage of npcm_i2c_master_xfer(), the address is
> stored with the shift and used in the i2c_recover_bus call().

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 1/6] i2c: npcm: correct the read/write operation procedure

[Andi Shyti]

Hi Tyrone,

On Fri, Sep 20, 2024 at 06:18:15PM GMT, warp5tw@gmail.com wrote:
> From: Tyrone Ting <kfting@nuvoton.com>
> 
> From: Tyrone Ting <kfting@nuvoton.com>

no worries, I can take care of this.

> Originally the driver uses the XMIT bit in SMBnST register to decide
> the upcoming i2c transaction. If XMIT bit is 1, then it will be an i2c
> write operation. If it's 0, then a read operation will be executed.
> 
> In slave mode the XMIT bit can simply be used directly to set the state.
> XMIT bit can be used as an indication to the current state of the state
> machine during slave operation. (meaning XMIT = 1 during writing and
> XMIT = 0 during reading).
> 
> In master operation XMIT is valid only if there are no bus errors.
> For example: in a multi master where the same module is switching from
> master to slave at runtime, and there are collisions, the XMIT bit
> cannot be trusted.
> 
> However the maser already "knows" what the bus state is, so this bit
> is not needed and the driver can just track what it is currently doing.
> 
> Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
> Reviewed-by: Tali Perry <tali.perry1@gmail.com>

This patch is independent from the rest of the series, can I
start takin this in and unburden you from this?

Andi

Re: [PATCH v4 2/6] i2c: npcm: use a software flag to indicate a BER condition

[Andi Shyti]

Hi Tyrone,

patch looks good, but...

On Fri, Sep 20, 2024 at 06:18:16PM GMT, warp5tw@gmail.com wrote:
> From: Tyrone Ting <kfting@nuvoton.com>
> 
> From: Tyrone Ting <kfting@nuvoton.com>
> 
> If not clearing the BB (bus busy) condition in the BER (bus error)
> interrupt, the driver causes a timeout and hence the i2c core
> doesn't do the i2c transfer retry but returns the driver's return
> value to the upper layer instead.
> 
> Clear the BB condition in the BER interrupt and a software flag is
> used. The driver does an i2c recovery without causing the timeout
> if the flag is set.
> 
> Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
> Reviewed-by: Tali Perry <tali.perry1@gmail.com>
> ---
>  drivers/i2c/busses/i2c-npcm7xx.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> index 2b76dbfba438..2d034503d8bc 100644
> --- a/drivers/i2c/busses/i2c-npcm7xx.c
> +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> @@ -334,6 +334,7 @@ struct npcm_i2c {
>  	u64 nack_cnt;
>  	u64 timeout_cnt;
>  	u64 tx_complete_cnt;
> +	bool ber_state;

I need some comment here, what is this ber state? You described
it in the commit log, but people won't be browsing much of the
commit log rather than the code itself.

You could perhaps mention the meaning as:

	bool ber_state; /* brief description */

and...

>  };
>  
>  static inline void npcm_i2c_select_bank(struct npcm_i2c *bus,
> @@ -1521,6 +1522,7 @@ static void npcm_i2c_irq_handle_ber(struct npcm_i2c *bus)
>  	if (npcm_i2c_is_master(bus)) {
>  		npcm_i2c_master_abort(bus);
>  	} else {
> +		bus->ber_state = true;
>  		npcm_i2c_clear_master_status(bus);
>  
>  		/* Clear BB (BUS BUSY) bit */
> @@ -1699,6 +1701,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
>  		dev_dbg(bus->dev, "bus%d-0x%x recovery skipped, bus not stuck",
>  			bus->num, bus->dest_addr);
>  		npcm_i2c_reset(bus);
> +		bus->ber_state = false;
>  		return 0;
>  	}
>  
> @@ -1763,6 +1766,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
>  		if (bus->rec_succ_cnt < ULLONG_MAX)
>  			bus->rec_succ_cnt++;
>  	}
> +	bus->ber_state = false;
>  	return status;
>  }
>  
> @@ -2158,7 +2162,7 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  
>  	} while (time_is_after_jiffies(time_left) && bus_busy);
>  
> -	if (bus_busy) {
> +	if (bus_busy || bus->ber_state) {

/*
 * Check the BER (bus error) state, if it's true means that blah
 * blah blah, while when it's false blah blah blah and we should
 * or should not do blah blah blah
 */
if (bus_busy || bus->ber_state) {
	...
}

Thanks,
Andi

>  		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
>  		npcm_i2c_reset(bus);
>  		i2c_recover_bus(adap);
> -- 
> 2.34.1
> 

Re: [PATCH v4 3/6] i2c: npcm: Modify timeout evaluation mechanism

[Andi Shyti]

Hi Tyrone,

...

> diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> index 2d034503d8bc..68f3d47323ab 100644
> --- a/drivers/i2c/busses/i2c-npcm7xx.c
> +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> @@ -2132,19 +2132,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  		}
>  	}
>  
> -	/*
> -	 * Adaptive TimeOut: estimated time in usec + 100% margin:
> -	 * 2: double the timeout for clock stretching case
> -	 * 9: bits per transaction (including the ack/nack)
> -	 */
> -	timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
> -	timeout = max_t(unsigned long, bus->adap.timeout, usecs_to_jiffies(timeout_usec));
>  	if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
>  		dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
>  		return -EINVAL;
>  	}
>  
> -	time_left = jiffies + timeout + 1;
> +	time_left = jiffies + bus->adap.timeout / bus->adap.retries + 1;
>  	do {
>  		/*
>  		 * we must clear slave address immediately when the bus is not
> @@ -2183,6 +2176,14 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  	if (npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
>  				       write_data, read_data, read_PEC,
>  				       read_block)) {
> +		/*
> +		 * Adaptive TimeOut: estimated time in usec + 100% margin:
> +		 * 2: double the timeout for clock stretching case
> +		 * 9: bits per transaction (including the ack/nack)
> +		 */
> +		timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
> +		timeout = max_t(unsigned long, bus->adap.timeout / bus->adap.retries,
> +				usecs_to_jiffies(timeout_usec));
>  		time_left = wait_for_completion_timeout(&bus->cmd_complete,
>  							timeout);
>  
> @@ -2308,7 +2309,7 @@ static int npcm_i2c_probe_bus(struct platform_device *pdev)
>  	adap = &bus->adap;
>  	adap->owner = THIS_MODULE;
>  	adap->retries = 3;
> -	adap->timeout = msecs_to_jiffies(35);
> +	adap->timeout = 2 * HZ;

Same here, I need some good description of why timeout is set to
2 seconds. If the datasheet says 35ms, I do not exclude that
someone in the future will send a patch saying "we don't need to
wait 2 seconds, wait 35ms as per datasheet".

Thanks,
Andi

>  	adap->algo = &npcm_i2c_algo;
>  	adap->quirks = &npcm_i2c_quirks;
>  	adap->algo_data = bus;
> -- 
> 2.34.1
> 

Re: [PATCH v4 1/6] i2c: npcm: correct the read/write operation procedure

[Tyrone Ting]

Hi Andi:

Thank you for your help.

Andi Shyti <andi.shyti@kernel.org> 於 2024年9月26日 週四 上午4:19寫道：
>
> Hi Tyrone,
>
> On Fri, Sep 20, 2024 at 06:18:15PM GMT, warp5tw@gmail.com wrote:
> > From: Tyrone Ting <kfting@nuvoton.com>
> >
> > From: Tyrone Ting <kfting@nuvoton.com>
>
> no worries, I can take care of this.
>
> > Originally the driver uses the XMIT bit in SMBnST register to decide
> > the upcoming i2c transaction. If XMIT bit is 1, then it will be an i2c
> > write operation. If it's 0, then a read operation will be executed.
> >
> > In slave mode the XMIT bit can simply be used directly to set the state.
> > XMIT bit can be used as an indication to the current state of the state
> > machine during slave operation. (meaning XMIT = 1 during writing and
> > XMIT = 0 during reading).
> >
> > In master operation XMIT is valid only if there are no bus errors.
> > For example: in a multi master where the same module is switching from
> > master to slave at runtime, and there are collisions, the XMIT bit
> > cannot be trusted.
> >
> > However the maser already "knows" what the bus state is, so this bit
> > is not needed and the driver can just track what it is currently doing.
> >
> > Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
> > Reviewed-by: Tali Perry <tali.perry1@gmail.com>
>
> This patch is independent from the rest of the series, can I
> start takin this in and unburden you from this?
>

Sure, thank you again.

> Andi

Regards,
Tyrone

Re: [PATCH v4 2/6] i2c: npcm: use a software flag to indicate a BER condition

[Tyrone Ting]

Hi Andi:

Thank you for your feedback.

Andi Shyti <andi.shyti@kernel.org> 於 2024年9月26日 週四 上午4:22寫道：
>
> Hi Tyrone,
>
> patch looks good, but...
>
> On Fri, Sep 20, 2024 at 06:18:16PM GMT, warp5tw@gmail.com wrote:
> > From: Tyrone Ting <kfting@nuvoton.com>
> >
> > From: Tyrone Ting <kfting@nuvoton.com>
> >
> > If not clearing the BB (bus busy) condition in the BER (bus error)
> > interrupt, the driver causes a timeout and hence the i2c core
> > doesn't do the i2c transfer retry but returns the driver's return
> > value to the upper layer instead.
> >
> > Clear the BB condition in the BER interrupt and a software flag is
> > used. The driver does an i2c recovery without causing the timeout
> > if the flag is set.
> >
> > Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
> > Reviewed-by: Tali Perry <tali.perry1@gmail.com>
> > ---
> >  drivers/i2c/busses/i2c-npcm7xx.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> > index 2b76dbfba438..2d034503d8bc 100644
> > --- a/drivers/i2c/busses/i2c-npcm7xx.c
> > +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> > @@ -334,6 +334,7 @@ struct npcm_i2c {
> >       u64 nack_cnt;
> >       u64 timeout_cnt;
> >       u64 tx_complete_cnt;
> > +     bool ber_state;
>
> I need some comment here, what is this ber state? You described
> it in the commit log, but people won't be browsing much of the
> commit log rather than the code itself.
>
> You could perhaps mention the meaning as:
>
>         bool ber_state; /* brief description */
>

Understood. I'll add some descriptions.

> and...
>
> >  };
> >
> >  static inline void npcm_i2c_select_bank(struct npcm_i2c *bus,
> > @@ -1521,6 +1522,7 @@ static void npcm_i2c_irq_handle_ber(struct npcm_i2c *bus)
> >       if (npcm_i2c_is_master(bus)) {
> >               npcm_i2c_master_abort(bus);
> >       } else {
> > +             bus->ber_state = true;
> >               npcm_i2c_clear_master_status(bus);
> >
> >               /* Clear BB (BUS BUSY) bit */
> > @@ -1699,6 +1701,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
> >               dev_dbg(bus->dev, "bus%d-0x%x recovery skipped, bus not stuck",
> >                       bus->num, bus->dest_addr);
> >               npcm_i2c_reset(bus);
> > +             bus->ber_state = false;
> >               return 0;
> >       }
> >
> > @@ -1763,6 +1766,7 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
> >               if (bus->rec_succ_cnt < ULLONG_MAX)
> >                       bus->rec_succ_cnt++;
> >       }
> > +     bus->ber_state = false;
> >       return status;
> >  }
> >
> > @@ -2158,7 +2162,7 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >
> >       } while (time_is_after_jiffies(time_left) && bus_busy);
> >
> > -     if (bus_busy) {
> > +     if (bus_busy || bus->ber_state) {
>
> /*
>  * Check the BER (bus error) state, if it's true means that blah
>  * blah blah, while when it's false blah blah blah and we should
>  * or should not do blah blah blah
>  */
> if (bus_busy || bus->ber_state) {
>         ...
> }
>

Understood. Your comments will be addressed.

> Thanks,
> Andi
>
> >               iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
> >               npcm_i2c_reset(bus);
> >               i2c_recover_bus(adap);
> > --
> > 2.34.1
> >

Thank you.

Regards,
Tyrone

Re: [PATCH v4 3/6] i2c: npcm: Modify timeout evaluation mechanism

[Tyrone Ting]

Hi Andi:

Thank you for your feedback.

Your comments will be addressed.

Andi Shyti <andi.shyti@kernel.org> 於 2024年9月26日 週四 上午4:24寫道：
>
> Hi Tyrone,
>
> ...
>
> > diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> > index 2d034503d8bc..68f3d47323ab 100644
> > --- a/drivers/i2c/busses/i2c-npcm7xx.c
> > +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> > @@ -2132,19 +2132,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >               }
> >       }
> >
> > -     /*
> > -      * Adaptive TimeOut: estimated time in usec + 100% margin:
> > -      * 2: double the timeout for clock stretching case
> > -      * 9: bits per transaction (including the ack/nack)
> > -      */
> > -     timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
> > -     timeout = max_t(unsigned long, bus->adap.timeout, usecs_to_jiffies(timeout_usec));
> >       if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
> >               dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
> >               return -EINVAL;
> >       }
> >
> > -     time_left = jiffies + timeout + 1;
> > +     time_left = jiffies + bus->adap.timeout / bus->adap.retries + 1;
> >       do {
> >               /*
> >                * we must clear slave address immediately when the bus is not
> > @@ -2183,6 +2176,14 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >       if (npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
> >                                      write_data, read_data, read_PEC,
> >                                      read_block)) {
> > +             /*
> > +              * Adaptive TimeOut: estimated time in usec + 100% margin:
> > +              * 2: double the timeout for clock stretching case
> > +              * 9: bits per transaction (including the ack/nack)
> > +              */
> > +             timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
> > +             timeout = max_t(unsigned long, bus->adap.timeout / bus->adap.retries,
> > +                             usecs_to_jiffies(timeout_usec));
> >               time_left = wait_for_completion_timeout(&bus->cmd_complete,
> >                                                       timeout);
> >
> > @@ -2308,7 +2309,7 @@ static int npcm_i2c_probe_bus(struct platform_device *pdev)
> >       adap = &bus->adap;
> >       adap->owner = THIS_MODULE;
> >       adap->retries = 3;
> > -     adap->timeout = msecs_to_jiffies(35);
> > +     adap->timeout = 2 * HZ;
>
> Same here, I need some good description of why timeout is set to
> 2 seconds. If the datasheet says 35ms, I do not exclude that
> someone in the future will send a patch saying "we don't need to
> wait 2 seconds, wait 35ms as per datasheet".
>
> Thanks,
> Andi
>
> >       adap->algo = &npcm_i2c_algo;
> >       adap->quirks = &npcm_i2c_quirks;
> >       adap->algo_data = bus;
> > --
> > 2.34.1
> >

Have a nice day.

Regards,
Tyrone