Re: [PATCH v8 2/2] i2c: ls2x: Add clocks property parsing and adjust bus speed

On Tue, 2026-07-21 at 20:26 +0800, Hongliang Wang wrote:
> The i2c-ls2x driver supports dts and acpi parameter passing.
> 
> In dts, uses clock framework, by parsing clocks property to
> get i2c bus reference clock, and define the div of reference
> clock by device data.
> 
> In acpi, by passing clocks property to describe i2c bus reference
> clock and clock-div property to describe the div of reference clock.
> 
> Based on i2c bus reference clock(clock_a), i2c bus speed(clock_s)
> and div, calculate the prcescale of i2c divider register. The
> calculation formula is
> 
> prcescale = (clock_a*10)/(div*clock_s)-1
> 
> Reviewed-by: Huacai Chen <[email protected]>
> Cc: [email protected]
> Signed-off-by: Hongliang Wang <[email protected]>

This resolves the jittery touchpad input on the EAECIS NL60R laptop.

Tested-by: Xi Ruoyao <[email protected]>

> ---
>  drivers/i2c/busses/i2c-ls2x.c | 40 ++++++++++++++++++++++++++++++++---
>  1 file changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-ls2x.c b/drivers/i2c/busses/i2c-ls2x.c
> index b475dd27b7af..25f8301ae14f 100644
> --- a/drivers/i2c/busses/i2c-ls2x.c
> +++ b/drivers/i2c/busses/i2c-ls2x.c
> @@ -12,6 +12,7 @@
>  
>  #include <linux/bitfield.h>
>  #include <linux/bits.h>
> +#include <linux/clk.h>
>  #include <linux/completion.h>
>  #include <linux/device.h>
>  #include <linux/iopoll.h>
> @@ -63,11 +64,19 @@
>  /* The default bus frequency, which is an empirical value */
>  #define LS2X_I2C_FREQ_STD	(33 * HZ_PER_KHZ)
>  
> +/* The div of i2c reference clock on LS2K0500/2K1000/2K2000 */
> +#define LS2X_I2C_2K_CLOCK_DIV	40
> +
> +/* The div of i2c reference clock on LS7A1000/7A2000 */
> +#define LS2X_I2C_7A_CLOCK_DIV	50
> +
>  struct ls2x_i2c_priv {
>  	struct i2c_adapter	adapter;
>  	void __iomem		*base;
>  	struct i2c_timings	i2c_t;
>  	struct completion	cmd_complete;
> +	unsigned int		div;
> +	unsigned int		pclk;
>  };
>  
>  /*
> @@ -107,12 +116,13 @@ static void ls2x_i2c_adjust_bus_speed(struct ls2x_i2c_priv *priv)
>  	else
>  		t->bus_freq_hz = LS2X_I2C_FREQ_STD;
>  
> +	val = (priv->pclk * 10) / (priv->div * t->bus_freq_hz) - 1;
> +
>  	/*
>  	 * According to the chip manual, we can only access the registers as bytes,
>  	 * otherwise the high bits will be truncated.
>  	 * So set the I2C frequency with a sequential writeb() instead of writew().
>  	 */
> -	val = LS2X_I2C_PCLK_FREQ / (5 * t->bus_freq_hz) - 1;
>  	writeb(FIELD_GET(GENMASK(7, 0), val), priv->base + I2C_LS2X_PRER_LO);
>  	writeb(FIELD_GET(GENMASK(15, 8), val), priv->base + I2C_LS2X_PRER_HI);
>  }
> @@ -287,6 +297,7 @@ static const struct i2c_algorithm ls2x_i2c_algo = {
>  static int ls2x_i2c_probe(struct platform_device *pdev)
>  {
>  	int ret, irq;
> +	struct clk *clk;
>  	struct i2c_adapter *adap;
>  	struct ls2x_i2c_priv *priv;
>  	struct device *dev = &pdev->dev;
> @@ -304,6 +315,29 @@ static int ls2x_i2c_probe(struct platform_device *pdev)
>  	if (irq < 0)
>  		return irq;
>  
> +	if (dev_of_node(dev)) {
> +		clk = devm_clk_get_optional_enabled(dev, NULL);
> +		if (IS_ERR(clk))
> +			return PTR_ERR(clk);
> +		if (clk)
> +			priv->pclk = clk_get_rate(clk);
> +		else
> +			priv->pclk = LS2X_I2C_PCLK_FREQ;
> +
> +		priv->div = (unsigned long)device_get_match_data(dev);
> +		if (!priv->div)
> +			priv->div = LS2X_I2C_2K_CLOCK_DIV;
> +	} else {
> +		/* clocks and clock-div are only ACPI properties. */
> +		ret = device_property_read_u32(dev, "clocks", &priv->pclk);
> +		if (ret)
> +			priv->pclk = LS2X_I2C_PCLK_FREQ;
> +
> +		ret = device_property_read_u32(dev, "clock-div", &priv->div);
> +		if (ret || !priv->div)
> +			priv->div = LS2X_I2C_7A_CLOCK_DIV;
> +	}
> +
>  	/* Add the i2c adapter */
>  	adap = &priv->adapter;
>  	adap->retries = 5;
> @@ -349,8 +383,8 @@ static DEFINE_RUNTIME_DEV_PM_OPS(ls2x_i2c_pm_ops,
>  				 ls2x_i2c_suspend, ls2x_i2c_resume, NULL);
>  
>  static const struct of_device_id ls2x_i2c_id_table[] = {
> -	{ .compatible = "loongson,ls2k-i2c" },
> -	{ .compatible = "loongson,ls7a-i2c" },
> +	{ .compatible = "loongson,ls2k-i2c", .data = (void *)LS2X_I2C_2K_CLOCK_DIV, },
> +	{ .compatible = "loongson,ls7a-i2c", .data = (void *)LS2X_I2C_7A_CLOCK_DIV, },
>  	{ /* sentinel */ }
>  };
>  MODULE_DEVICE_TABLE(of, ls2x_i2c_id_table);

-- 
Xi Ruoyao <[email protected]>