diff mbox series

[v7,3/4] i2c: npcm: use i2c frequency table

Message ID 20241021062732.5592-4-kfting@nuvoton.com
State Superseded
Headers show
Series i2c: npcm: read/write operation, checkpatch | expand

Commit Message

Tyrone Ting Oct. 21, 2024, 6:27 a.m. UTC 
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(-)

Comments

Andi Shyti Oct. 24, 2024, 10:20 a.m. UTC | #1 
Hi Tyrone,

...

> -	/* 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;

There is here a slight change of behaiour which is not mentioned
in the commit log. Before the user could set a bus_freq_hz which
had to be <= I2C_MAX_..._MODE_FREQ, while now it has to be
precisely that.

Do we want to check what the user has set in the DTS?

(Or am I missing something?)

Thanks,
Andi
Tyrone Ting Oct. 25, 2024, 1:46 a.m. UTC | #2 
Hi Andi:

Thank you for your comments.

Andi Shyti <andi.shyti@kernel.org> 於 2024年10月24日 週四 下午6:20寫道：
>
> Hi Tyrone,
>
> ...
>
> > -     /* 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;
>
> There is here a slight change of behaiour which is not mentioned
> in the commit log. Before the user could set a bus_freq_hz which
> had to be <= I2C_MAX_..._MODE_FREQ, while now it has to be
> precisely that.
>
> Do we want to check what the user has set in the DTS?

The driver checks the bus frequency the user sets in the DTS.

Please refer to the links:
1. https://github.com/torvalds/linux/blob/master/drivers/i2c/busses/i2c-npcm7xx.c#L1995
2. https://github.com/torvalds/linux/blob/master/drivers/i2c/busses/i2c-npcm7xx.c#L2002

>
> (Or am I missing something?)
>
> Thanks,
> Andi

Thank you.

Regards,
Tyrone
Tyrone Ting Nov. 5, 2024, 1:53 a.m. UTC | #3 
Hi Andi:

May I have your comments about my feedback on these patches?

Tyrone Ting <warp5tw@gmail.com> 於 2024年10月25日 週五 上午9:46寫道：
>
> Hi Andi:
>
> Thank you for your comments.
>
> Andi Shyti <andi.shyti@kernel.org> 於 2024年10月24日 週四 下午6:20寫道：
> >
> > Hi Tyrone,
> >
> > ...
> >
> > > -     /* 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;
> >
> > There is here a slight change of behaiour which is not mentioned
> > in the commit log. Before the user could set a bus_freq_hz which
> > had to be <= I2C_MAX_..._MODE_FREQ, while now it has to be
> > precisely that.
> >
> > Do we want to check what the user has set in the DTS?
>
> The driver checks the bus frequency the user sets in the DTS.
>
> Please refer to the links:
> 1. https://github.com/torvalds/linux/blob/master/drivers/i2c/busses/i2c-npcm7xx.c#L1995
> 2. https://github.com/torvalds/linux/blob/master/drivers/i2c/busses/i2c-npcm7xx.c#L2002
>
> >
> > (Or am I missing something?)
> >
> > Thanks,
> > Andi
>
> Thank you.
>
> Regards,
> Tyrone

Thank you.

Regards,
Tyrone
Andi Shyti Nov. 19, 2024, 10:25 p.m. UTC | #4 
Hi Tyrone,

...

> > > -     /* 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;
> >
> > There is here a slight change of behaiour which is not mentioned
> > in the commit log. Before the user could set a bus_freq_hz which
> > had to be <= I2C_MAX_..._MODE_FREQ, while now it has to be
> > precisely that.
> >
> > Do we want to check what the user has set in the DTS?
> 
> The driver checks the bus frequency the user sets in the DTS.

yes, but before it was checking the value within a range, while
now it's checking the exact value.

The difference is that now if you don't set the exact value you
get EINVAL, not before.

Andi
Tali Perry Nov. 21, 2024, 10:11 a.m. UTC | #5 
Hi Andi,

>
> > > > -     /* 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;
> > >
> > > There is here a slight change of behaiour which is not mentioned
> > > in the commit log. Before the user could set a bus_freq_hz which
> > > had to be <= I2C_MAX_..._MODE_FREQ, while now it has to be
> > > precisely that.
> > >
> > > Do we want to check what the user has set in the DTS?
> >
> > The driver checks the bus frequency the user sets in the DTS.
>
> yes, but before it was checking the value within a range, while
> now it's checking the exact value.
>
> The difference is that now if you don't set the exact value you
> get EINVAL, not before.
>
> Andi

Previously the driver was rounding numbers down.
The driver has settings for 100, 400, 1000 KHz.
but what happens if the user asks for 200KHz?
Some of the coefficients were calculated according to the equations,
and some were hard-coded values per setting.
We don't want to support this mix.
We prefer the users to ask for numbers that are one of the three
supported values and block unknown input values.

Thanks ,
Tali
diff mbox series

Patch

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index a9a9b21f1f0b..7c13f9f6014a 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);