Re: [PATCH] i2c: riic: Add Runtime PM support

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Hi Geert,

Thanks for your work.

On 2019-03-20 11:30:03 +0100, Geert Uytterhoeven wrote:
>   - Replace explicit clock handling by Runtime PM calls,
>   - Streamline Runtime PM handling in error paths,
>   - Enable Runtime PM in .probe(),
>   - Disable Runtime PM in .remove(),
>   - Make sure the device is runtime-resumed when disabling interrupts in
>     .remove().

Thanks for this change, it was educational for me to review.

> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>

> ---
> I don't think it's worth splitting off the last bug fix in a separate
> (first) patch, using explicit clock handling, as that will be replaced
> immediately by Runtime PM calls.
> ---
>  drivers/i2c/busses/i2c-riic.c | 43 +++++++++++++++++++----------------
>  1 file changed, 24 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-riic.c b/drivers/i2c/busses/i2c-riic.c
> index b75ff144b5704293..f31413fd9521ef9f 100644
> --- a/drivers/i2c/busses/i2c-riic.c
> +++ b/drivers/i2c/busses/i2c-riic.c
> @@ -43,6 +43,7 @@
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  
>  #define RIIC_ICCR1	0x00
>  #define RIIC_ICCR2	0x04
> @@ -112,12 +113,10 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  {
>  	struct riic_dev *riic = i2c_get_adapdata(adap);
>  	unsigned long time_left;
> -	int i, ret;
> +	int i;
>  	u8 start_bit;
>  
> -	ret = clk_prepare_enable(riic->clk);
> -	if (ret)
> -		return ret;
> +	pm_runtime_get_sync(adap->dev.parent);
>  
>  	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
>  		riic->err = -EBUSY;
> @@ -150,7 +149,7 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  	}
>  
>   out:
> -	clk_disable_unprepare(riic->clk);
> +	pm_runtime_put(adap->dev.parent);
>  
>  	return riic->err ?: num;
>  }
> @@ -281,20 +280,18 @@ static const struct i2c_algorithm riic_algo = {
>  
>  static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
>  {
> -	int ret;
> +	int ret = 0;
>  	unsigned long rate;
>  	int total_ticks, cks, brl, brh;
>  
> -	ret = clk_prepare_enable(riic->clk);
> -	if (ret)
> -		return ret;
> +	pm_runtime_get_sync(riic->adapter.dev.parent);
>  
>  	if (t->bus_freq_hz > 400000) {
>  		dev_err(&riic->adapter.dev,
>  			"unsupported bus speed (%dHz). 400000 max\n",
>  			t->bus_freq_hz);
> -		clk_disable_unprepare(riic->clk);
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  
>  	rate = clk_get_rate(riic->clk);
> @@ -332,8 +329,8 @@ static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
>  	if (brl > (0x1F + 3)) {
>  		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
>  			(unsigned long)t->bus_freq_hz);
> -		clk_disable_unprepare(riic->clk);
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  
>  	brh = total_ticks - brl;
> @@ -378,9 +375,9 @@ static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
>  
>  	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
>  
> -	clk_disable_unprepare(riic->clk);
> -
> -	return 0;
> +out:
> +	pm_runtime_put(riic->adapter.dev.parent);
> +	return ret;
>  }
>  
>  static struct riic_irq_desc riic_irqs[] = {
> @@ -439,28 +436,36 @@ static int riic_i2c_probe(struct platform_device *pdev)
>  
>  	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);
>  
> +	pm_runtime_enable(&pdev->dev);
> +
>  	ret = riic_init_hw(riic, &i2c_t);
>  	if (ret)
> -		return ret;
> -
> +		goto out;
>  
>  	ret = i2c_add_adapter(adap);
>  	if (ret)
> -		return ret;
> +		goto out;
>  
>  	platform_set_drvdata(pdev, riic);
>  
>  	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
>  		 i2c_t.bus_freq_hz);
>  	return 0;
> +
> +out:
> +	pm_runtime_disable(&pdev->dev);
> +	return ret;
>  }
>  
>  static int riic_i2c_remove(struct platform_device *pdev)
>  {
>  	struct riic_dev *riic = platform_get_drvdata(pdev);
>  
> +	pm_runtime_get_sync(&pdev->dev);
>  	writeb(0, riic->base + RIIC_ICIER);
> +	pm_runtime_put(&pdev->dev);
>  	i2c_del_adapter(&riic->adapter);
> +	pm_runtime_disable(&pdev->dev);
>  
>  	return 0;
>  }
> -- 
> 2.17.1
> 

-- 
Regards,
Niklas Söderlund



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