Re: [PATCH v4 0/1] i2c: mediatek: add runtime PM operations and bus regulator control

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

Il 11/02/25 15:39, Zoie Lin ha scritto:
> Introduce support for runtime PM operations in
> the I2C driver, enabling runtime suspend and resume functionality.
> 
> Although in most platforms, the bus power of i2c is always
> on, some platforms disable the i2c bus power in order to meet
> low power request.
> 
> This implementation includes bus regulator control to facilitate
> proper handling of the bus power based on platform requirements.
> 
> Signed-off-by: Zoie Lin <zoie.lin@mediatek.com>
> ---
>   drivers/i2c/busses/i2c-mt65xx.c | 73 +++++++++++++++++++++++++++------
>   1 file changed, 61 insertions(+), 12 deletions(-)
> 
> This series is based on linux-next, tag: next-20250210
> 
> Changes in v4:
> - Removed unnecessary variable initialization.
> - Removed unnecessary brackets.
> - Corrected grammar issues in the commit message.
> - Confirmed autosuspend delay is not necessary.

Turning on and off regulators at start of transfer and end of transfer respectively
is very expensive and, while it makes sense for power efficiency of the controller,
it doesn't make sense for:

  1. Responsiveness (latency); and
  2. Platform power efficiency at a whole.

As a start, just set the autosuspend delay to 250ms; this gives you at least time
to bring up clocks and regulators and usually finish a transfer at 400KHz, giving
you the chance to also get some more requests before autosuspend decides to, well,
auto..suspend the device.

The right way of choosing an autosuspend delay a bit more precisely, though, for
this device, would be to check the bus speed and calculate the autosuspend time
accordingly.

Cheers,
Angelo

> 
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index 5bd342047d59..1979b46d75f0 100644
> --- a/drivers/i2c/busses/i2c-mt65xx.c
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -21,6 +21,7 @@
>   #include <linux/module.h>
>   #include <linux/of.h>
>   #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>   #include <linux/scatterlist.h>
>   #include <linux/sched.h>
>   #include <linux/slab.h>
> @@ -1245,8 +1246,8 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
>   	int left_num = num;
>   	struct mtk_i2c *i2c = i2c_get_adapdata(adap);
>   
> -	ret = clk_bulk_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> -	if (ret)
> +	ret = pm_runtime_resume_and_get(i2c->dev);
> +	if (ret < 0)
>   		return ret;
>   
>   	i2c->auto_restart = i2c->dev_comp->auto_restart;
> @@ -1299,7 +1300,9 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
>   	ret = num;
>   
>   err_exit:
> -	clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	pm_runtime_mark_last_busy(i2c->dev);
> +	pm_runtime_put_sync(i2c->dev);
> +
>   	return ret;
>   }
>   
> @@ -1370,6 +1373,38 @@ static int mtk_i2c_parse_dt(struct device_node *np, struct mtk_i2c *i2c)
>   	return 0;
>   }
>   
> +static int mtk_i2c_runtime_suspend(struct device *dev)
> +{
> +	struct mtk_i2c *i2c = dev_get_drvdata(dev);
> +
> +	clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	if (i2c->adap.bus_regulator)
> +		regulator_disable(i2c->adap.bus_regulator);
> +
> +	return 0;
> +}
> +
> +static int mtk_i2c_runtime_resume(struct device *dev)
> +{
> +	int ret;
> +	struct mtk_i2c *i2c = dev_get_drvdata(dev);
> +
> +	if (i2c->adap.bus_regulator) {
> +		ret = regulator_enable(i2c->adap.bus_regulator);
> +		if (ret) {
> +			dev_err(dev, "enable regulator failed!\n");
> +			return ret;
> +		}
> +	}
> +
> +	ret = clk_bulk_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	if (ret)
> +		if (i2c->adap.bus_regulator)
> +			regulator_disable(i2c->adap.bus_regulator);
> +
> +	return ret;
> +}
> +
>   static int mtk_i2c_probe(struct platform_device *pdev)
>   {
>   	int ret = 0;
> @@ -1472,13 +1507,18 @@ static int mtk_i2c_probe(struct platform_device *pdev)
>   		}
>   	}
>   
> -	ret = clk_bulk_prepare_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	ret = clk_bulk_prepare(I2C_MT65XX_CLK_MAX, i2c->clocks);
>   	if (ret) {
> -		dev_err(&pdev->dev, "clock enable failed!\n");
>   		return ret;
>   	}
> +
> +	platform_set_drvdata(pdev, i2c);
> +
> +	ret = mtk_i2c_runtime_resume(i2c->dev);
> +	if (ret < 0)
> +		goto err_clk_bulk_unprepare;
>   	mtk_i2c_init_hw(i2c);
> -	clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	mtk_i2c_runtime_suspend(i2c->dev);
>   
>   	ret = devm_request_irq(&pdev->dev, irq, mtk_i2c_irq,
>   			       IRQF_NO_SUSPEND | IRQF_TRIGGER_NONE,
> @@ -1486,19 +1526,20 @@ static int mtk_i2c_probe(struct platform_device *pdev)
>   	if (ret < 0) {
>   		dev_err(&pdev->dev,
>   			"Request I2C IRQ %d fail\n", irq);
> -		goto err_bulk_unprepare;
> +		goto err_clk_bulk_unprepare;
>   	}
> +	pm_runtime_enable(&pdev->dev);
>   
>   	i2c_set_adapdata(&i2c->adap, i2c);
>   	ret = i2c_add_adapter(&i2c->adap);
>   	if (ret)
> -		goto err_bulk_unprepare;
> -
> -	platform_set_drvdata(pdev, i2c);
> +		goto err_pm_runtime_disable;
>   
>   	return 0;
>   
> -err_bulk_unprepare:
> +err_pm_runtime_disable:
> +	pm_runtime_disable(&pdev->dev);
> +err_clk_bulk_unprepare:
>   	clk_bulk_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks);
>   
>   	return ret;
> @@ -1510,6 +1551,7 @@ static void mtk_i2c_remove(struct platform_device *pdev)
>   
>   	i2c_del_adapter(&i2c->adap);
>   
> +	pm_runtime_disable(&pdev->dev);
>   	clk_bulk_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks);
>   }
>   
> @@ -1518,6 +1560,10 @@ static int mtk_i2c_suspend_noirq(struct device *dev)
>   	struct mtk_i2c *i2c = dev_get_drvdata(dev);
>   
>   	i2c_mark_adapter_suspended(&i2c->adap);
> +
> +	if (!pm_runtime_status_suspended(dev))
> +		mtk_i2c_runtime_suspend(dev);
> +
>   	clk_bulk_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks);
>   
>   	return 0;
> @@ -1536,7 +1582,8 @@ static int mtk_i2c_resume_noirq(struct device *dev)
>   
>   	mtk_i2c_init_hw(i2c);
>   
> -	clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	if (pm_runtime_status_suspended(dev))
> +		mtk_i2c_runtime_resume(dev);
>   
>   	i2c_mark_adapter_resumed(&i2c->adap);
>   
> @@ -1546,6 +1593,8 @@ static int mtk_i2c_resume_noirq(struct device *dev)
>   static const struct dev_pm_ops mtk_i2c_pm = {
>   	NOIRQ_SYSTEM_SLEEP_PM_OPS(mtk_i2c_suspend_noirq,
>   				  mtk_i2c_resume_noirq)
> +	SET_RUNTIME_PM_OPS(mtk_i2c_runtime_suspend, mtk_i2c_runtime_resume,
> +			   NULL)
>   };
>   
>   static struct platform_driver mtk_i2c_driver = {