Re: [v1,1/1] i2c: mediatek: add runtime PM operations and bus regulator control

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

Il 20/09/24 16:36, zoie.lin ha scritto:
> This commit introduces support for runtime PM operations in
> the I2C driver, enabling runtime suspend and resume functionality.
> 
> Although in the most platforms, the bus power of i2c are 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>

Hello Zoie,

Your name does not technically have any "." inside, so please fix it
so that it reads `Zoie Lin <zoie.lin@mediatek.com>`.

Moreover, this implementation can be improved. Check below:

You missed pm_runtime_status_suspended() checks in suspend/resume callbacks
and, if the bus wasn't already runtime suspended when reaching suspend(), that
will not get the bus regulators powered off when suspending; analogously, if
the device was runtime suspended, the regulators and clocks will stay on when
resuming from system sleep until first usage.

So add the checks:

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;
}

static int mtk_i2c_resume_noirq(struct device *dev)
{
	int ret;
	struct mtk_i2c *i2c = dev_get_drvdata(dev);

	ret = clk_bulk_prepare_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
	if (ret) {
		dev_err(dev, "clock enable failed!\n");
		return ret;
	}

	mtk_i2c_init_hw(i2c);

	if (pm_runtime_status_suspended(dev))
		ret = mtk_i2c_runtime_suspend(dev);

	i2c_mark_adapter_resumed(&i2c->adap);

	return 0;
}

> ---
>   drivers/i2c/busses/i2c-mt65xx.c | 72 ++++++++++++++++++++++++++++-----
>   1 file changed, 61 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index e0ba653dec2d..aae0189ba210 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_get_sync(i2c->dev);

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_autosuspend(i2c->dev);
> +
>   	return ret;
>   }
>   
> @@ -1370,6 +1373,41 @@ 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 = 0;
> +	struct mtk_i2c *i2c = dev_get_drvdata(dev);

struct mtk_i2c *i2c = dev_get_drvdata(dev);
int ret;

> +
> +	if (i2c->adap.bus_regulator) {
> +		ret = regulator_enable(i2c->adap.bus_regulator);
> +		if (ret < 0) {

`ret` can't be > 0. `if (ret) {` is enough.

> +			dev_err(dev, "enable regulator failed!\n");
> +			return ret;
> +		}
> +	}
> +
> +	ret = clk_bulk_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> +	if (ret < 0) {

if (ret) {

> +		dev_err(dev, "clock enable failed!\n");

This print is unnecessary.

> +		if (i2c->adap.bus_regulator)
> +			regulator_disable(i2c->adap.bus_regulator);
> +		return ret;
> +	}
> +
> +	return ret;

return 0;

> +}
> +
>   static int mtk_i2c_probe(struct platform_device *pdev)
>   {
>   	int ret = 0;
> @@ -1472,13 +1510,19 @@ 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");
> +		dev_err(&pdev->dev, "clk_bulk_prepare failed\n");

This print is anyway redundant, as clk_bulk_prepare() already prints upon failures,
so you can as well simply remove it instead of changing it.

>   		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 +1530,22 @@ 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_set_autosuspend_delay(&pdev->dev, 1000);

One full second as autosuspend delay? Can this be shortened to 500? 250?

How was the one second wait chosen?

How much time does mtk_i2c_runtime_resume() take to resume the bus?

> +	pm_runtime_use_autosuspend(&pdev->dev);
> +	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 +1557,7 @@ static void mtk_i2c_remove(struct platform_device *pdev)
>   
>   	i2c_del_adapter(&i2c->adap);
>   
> +	pm_runtime_disable(&pdev->dev);

pm_runtime_set_suspended(&pdev->dev);

>   	clk_bulk_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks);
>   }
>   

Regards,
Angelo