Re: [PATCH v12 5/7] i2c: davinci: add support for setting bus frequency

[Peter Rosin]

Hi!

On 2026-07-19 16:59, Marcus Folkesson wrote:
> Populate adapter with clock_Hz and .set_clk_freq() to enable support for
> dynamic bus frequency.
> 
> Remove bus_freq_Hz entirely and only use clock_Hz instead.
> 
> Acked-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> Signed-off-by: Marcus Folkesson <marcus.folkesson@xxxxxxxxx>
> ---
>  drivers/i2c/busses/i2c-davinci.c | 33 +++++++++++++++++++++++++--------
>  1 file changed, 25 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> index f543997c31e9..87fef17bca55 100644
> --- a/drivers/i2c/busses/i2c-davinci.c
> +++ b/drivers/i2c/busses/i2c-davinci.c
> @@ -132,8 +132,6 @@ struct davinci_i2c_dev {
>  #ifdef CONFIG_CPU_FREQ
>  	struct notifier_block	freq_transition;
>  #endif
> -	/* standard bus frequency */
> -	unsigned int		bus_freq_Hz;
>  	/* Chip has a ICPFUNC register */
>  	bool			has_pfunc;
>  };
> @@ -171,6 +169,7 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
>  	u32 clkh;
>  	u32 clkl;
>  	u32 input_clock = clk_get_rate(dev->clk);
> +	u32 bus_freq_Hz = dev->adapter.clock_Hz;
>  
>  	/* NOTE: I2C Clock divider programming info
>  	 * As per I2C specs the following formulas provide prescaler
> @@ -207,16 +206,16 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
>  	if (device_is_compatible(dev->dev, "ti,keystone-i2c"))
>  		d = 6;
>  
> -	clk = (input_clock / (psc + 1)) / (dev->bus_freq_Hz);
> +	clk = (input_clock / (psc + 1)) / (bus_freq_Hz);

Repeat bracket comment from 4/7. I.e.

	clk = input_clock / (psc + 1) / bus_freq_Hz;

Cheers,
Peter

>  	/* Avoid driving the bus too fast because of rounding errors above */
> -	if (input_clock / (psc + 1) / clk > dev->bus_freq_Hz)
> +	if (input_clock / (psc + 1) / clk > bus_freq_Hz)
>  		clk++;
>  	/*
>  	 * According to I2C-BUS Spec 2.1, in FAST-MODE LOW period should be at
>  	 * least 1.3uS, which is not the case with 50% duty cycle. Driving HIGH
>  	 * to LOW ratio as 1 to 2 is more safe.
>  	 */
> -	if (dev->bus_freq_Hz > I2C_MAX_STANDARD_MODE_FREQ)
> +	if (bus_freq_Hz > I2C_MAX_STANDARD_MODE_FREQ)
>  		clkl = (clk << 1) / 3;
>  	else
>  		clkl = (clk >> 1);
> @@ -267,7 +266,7 @@ static int i2c_davinci_init(struct davinci_i2c_dev *dev)
>  		davinci_i2c_read_reg(dev, DAVINCI_I2C_CLKL_REG));
>  	dev_dbg(dev->dev, "CLKH = %d\n",
>  		davinci_i2c_read_reg(dev, DAVINCI_I2C_CLKH_REG));
> -	dev_dbg(dev->dev, "bus_freq_Hz = %dHz\n", dev->bus_freq_Hz);
> +	dev_dbg(dev->dev, "bus_freq_Hz = %dHz\n", dev->adapter.clock_Hz);
>  
>  
>  	/* Take the I2C module out of reset: */
> @@ -279,6 +278,23 @@ static int i2c_davinci_init(struct davinci_i2c_dev *dev)
>  	return 0;
>  }
>  
> +static int davinci_i2c_set_clk(struct i2c_adapter *adap, u32 clock_Hz)
> +{
> +	struct davinci_i2c_dev *dev = i2c_get_adapdata(adap);
> +
> +	/* put I2C into reset */
> +	davinci_i2c_reset_ctrl(dev, 0);
> +
> +	/* compute clock dividers */
> +	adap->clock_Hz = clock_Hz;
> +	i2c_davinci_calc_clk_dividers(dev);
> +
> +	/* Take the I2C module out of reset: */
> +	davinci_i2c_reset_ctrl(dev, 1);
> +
> +	return clock_Hz;
> +}
> +
>  /*
>   * This routine does i2c bus recovery by using i2c_generic_scl_recovery
>   * which is provided by I2C Bus recovery infrastructure.
> @@ -755,12 +771,13 @@ static int davinci_i2c_probe(struct platform_device *pdev)
>  	dev->dev = &pdev->dev;
>  	dev->irq = irq;
>  	platform_set_drvdata(pdev, dev);
> +	adap = &dev->adapter;
>  
>  	r = device_property_read_u32(&pdev->dev, "clock-frequency", &prop);
>  	if (r)
>  		prop = I2C_MAX_STANDARD_MODE_FREQ;
>  
> -	dev->bus_freq_Hz = prop;
> +	adap->clock_Hz = prop;
>  
>  	dev->has_pfunc = device_property_present(&pdev->dev, "ti,has-pfunc");
>  
> @@ -800,7 +817,6 @@ static int davinci_i2c_probe(struct platform_device *pdev)
>  		goto err_unuse_clocks;
>  	}
>  
> -	adap = &dev->adapter;
>  	i2c_set_adapdata(adap, dev);
>  	adap->owner = THIS_MODULE;
>  	adap->class = I2C_CLASS_DEPRECATED;
> @@ -809,6 +825,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
>  	adap->dev.parent = &pdev->dev;
>  	adap->timeout = DAVINCI_I2C_TIMEOUT;
>  	adap->dev.of_node = dev_of_node(&pdev->dev);
> +	adap->set_clk_freq = davinci_i2c_set_clk;
>  
>  	if (dev->has_pfunc)
>  		adap->bus_recovery_info = &davinci_i2c_scl_recovery_info;
>