[PATCH v6 0/4] i2c: npcm: read/write operation, checkpatch

[PATCH v6 0/4] i2c: npcm: read/write operation, checkpatch

[Tyrone Ting]

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/lkml/CACD3sJYhAYV3zBse5ntF
  sQmLV+TpLKtOiyyqgp3g8qeja54Ejw@mail.gmail.com/
- Andy Shevchenko : https://lore.kernel.org/lkml/ZwVcGu3YeJ6pI0sM
  @black.fi.intel.com/
- Andy Shevchenko : https://lore.kernel.org/lkml/Zvv3ws1_jUMVnAAJ
  @smile.fi.intel.com/

Changes since version 5:
- Correct "EAGAIN" to "-EAGAIN" in the commit message.
- Configure the bus->dest_addr by calling i2c_8bit_addr_from_msg()
  and remove the I2C_M_RD flag when calling i2c_recover_bus().
- Fix the commit message which meets a too small wrapping limit.

Changes since version 4:
- Add more description for the codes.
- Modify the term "function" to "function()" in the commit message
and code comments.

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 (3):
  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 | 428 ++++++++++++++++++++++++-------
 1 file changed, 332 insertions(+), 96 deletions(-)


base-commit: 663bff1ddfe4ecbba3bcf4a74646bb388b1ad5b2
-- 
2.34.1

[PATCH v6 1/4] i2c: npcm: Modify timeout evaluation mechanism

[Tyrone Ting]

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 | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 482a0074d448..c96a25d37c14 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
@@ -2192,6 +2185,14 @@ 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);
 
@@ -2317,7 +2318,12 @@ 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);
+	/*
+	 * 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.
+	 */
+	adap->timeout = 2 * HZ;
 	adap->algo = &npcm_i2c_algo;
 	adap->quirks = &npcm_i2c_quirks;
 	adap->algo_data = bus;
-- 
2.34.1

[PATCH v6 2/4] i2c: npcm: Modify the client address assignment

[Tyrone Ting]

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
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 | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index c96a25d37c14..349492f114e7 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -2155,6 +2155,19 @@ 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 npcm_i2c_master_xfer(), the address is stored with
+	 * the shift and used in the i2c_recover_bus().
+	 *
+	 * 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 = i2c_8bit_addr_from_msg(msg0);
+
 	/*
 	 * Check the BER (bus error) state, when ber_state is true, it means that the module
 	 * detects the bus error which is caused by some factor like that the electricity
@@ -2165,6 +2178,16 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	 * bus is busy.
 	 */
 	if (bus_busy || bus->ber_state) {
+		/*
+		 * Since the transfer might be a read operation, remove the I2C_M_RD flag
+		 * from the bus->dest_addr for the i2c_recover_bus() call later.
+		 *
+		 * The i2c_recover_bus() uses the address in a write direction to recover
+		 * the i2c bus if some error condition occurs.
+		 */
+		if (bus->dest_addr & I2C_M_RD)
+			bus->dest_addr &= ~I2C_M_RD;
+
 		iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
 		npcm_i2c_reset(bus);
 		i2c_recover_bus(adap);
@@ -2172,7 +2195,6 @@ 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 v6 3/4] i2c: npcm: use i2c frequency table

[Tyrone Ting]

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 349492f114e7..fcecb098298f 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 v6 4/4] i2c: npcm: Enable slave in eob interrupt

[Tyrone Ting]

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 fcecb098298f..55348308b992 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 v6 2/4] i2c: npcm: Modify the client address assignment

[Andy Shevchenko]

On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:
> 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
> npcm_i2c_master_xfer().

...

> +	/*
> +	 * 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().
> +	 *
> +	 * 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.
> +	 */

I would rephrase it a bit like

	/*
	 * Previously, the 7-bit address was stored and being converted to
	 * the address of event 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 of event is stored
	 * and then used in the i2c_recover_bus().
	 */

(E.g., the last paragraph just describes 101 about I2C 7-bit addresses usage
 and may be dropped completely.)

> +	bus->dest_addr = i2c_8bit_addr_from_msg(msg0);

...

> +		/*
> +		 * Since the transfer might be a read operation, remove the I2C_M_RD flag
> +		 * from the bus->dest_addr for the i2c_recover_bus() call later.
> +		 *
> +		 * The i2c_recover_bus() uses the address in a write direction to recover
> +		 * the i2c bus if some error condition occurs.
> +		 */

> +		if (bus->dest_addr & I2C_M_RD)

Redundant.

> +			bus->dest_addr &= ~I2C_M_RD;

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 4/4] i2c: npcm: Enable slave in eob interrupt

[Andy Shevchenko]

On Fri, Oct 11, 2024 at 01:52:31PM +0800, Tyrone Ting wrote:
> 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.

...

> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +		/* reenable slave if it was enabled */
> +		if (bus->slave)
> +			iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,

GENMASK()?
But why do we need it? Do we expect this to be 10-bit address or...?

> +				 bus->reg + NPCM_I2CADDR1);
> +#endif

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 2/4] i2c: npcm: Modify the client address assignment

[Tyrone Ting]

Hi Andy:

Thank you for your comments.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年10月11日 週五 下午7:00寫道：
>
> On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:
> > 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
> > npcm_i2c_master_xfer().
>
> ...
>
> > +     /*
> > +      * 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().
> > +      *
> > +      * 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.
> > +      */
>
> I would rephrase it a bit like
>
>         /*
>          * Previously, the 7-bit address was stored and being converted to
>          * the address of event 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 of event is stored
>          * and then used in the i2c_recover_bus().
>          */
>
> (E.g., the last paragraph just describes 101 about I2C 7-bit addresses usage
>  and may be dropped completely.)
>

Understood. I'll modify the comments and remove the last paragraph.

> > +     bus->dest_addr = i2c_8bit_addr_from_msg(msg0);
>
> ...
>
> > +             /*
> > +              * Since the transfer might be a read operation, remove the I2C_M_RD flag
> > +              * from the bus->dest_addr for the i2c_recover_bus() call later.
> > +              *
> > +              * The i2c_recover_bus() uses the address in a write direction to recover
> > +              * the i2c bus if some error condition occurs.
> > +              */
>
> > +             if (bus->dest_addr & I2C_M_RD)
>
> Redundant.
>

Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?

> > +                     bus->dest_addr &= ~I2C_M_RD;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Thank you again.

Regards,
Tyrone

Re: [PATCH v6 2/4] i2c: npcm: Modify the client address assignment

[Andy Shevchenko]

On Fri, Oct 11, 2024 at 09:44:42PM +0800, Tyrone Ting wrote:
> > On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:

...

> > > +             if (bus->dest_addr & I2C_M_RD)
> >
> > Redundant.
> 
> Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?

Yes.

> > > +                     bus->dest_addr &= ~I2C_M_RD;

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 2/4] 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10月11日 週五 下午9:58寫道：
>
> On Fri, Oct 11, 2024 at 09:44:42PM +0800, Tyrone Ting wrote:
> > > On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:
>
> ...
>
> > > > +             if (bus->dest_addr & I2C_M_RD)
> > >
> > > Redundant.
> >
> > Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?
>
> Yes.
>
> > > > +                     bus->dest_addr &= ~I2C_M_RD;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Have a nice day.

Regards,
Tyrone

Re: [PATCH v6 4/4] i2c: npcm: Enable slave in eob interrupt

[Tyrone Ting]

Hi Andy:

Thank you for your feedback.

Andy Shevchenko <andriy.shevchenko@linux.intel.com> 於 2024年10月11日 週五 下午7:02寫道：
>
> On Fri, Oct 11, 2024 at 01:52:31PM +0800, Tyrone Ting wrote:
> > 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.
>
> ...
>
> > +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> > +             /* reenable slave if it was enabled */
> > +             if (bus->slave)
> > +                     iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,
>
> GENMASK()?
> But why do we need it? Do we expect this to be 10-bit address or...?
>

0x7f is going to be removed in the next patch set.

> > +                              bus->reg + NPCM_I2CADDR1);
> > +#endif
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Thank you.

Regards,
Tyrone