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Date:   Thu, 28 Jan 2021 10:22:08 +0100
From:   Wolfram Sang <wsa@...nel.org>
To:     Samuel Holland <samuel@...lland.org>
Cc:     Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-i2c@...r.kernel.org, Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Ondrej Jirman <megous@...ous.com>,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH] i2c: mv64xxx: Add runtime PM support

On Sun, Jan 03, 2021 at 04:51:46AM -0600, Samuel Holland wrote:
> To save power, gate the clock when the bus is inactive, during system
> sleep, and during shutdown. On some platforms, specifically Allwinner
> A13/A20, gating the clock implicitly resets the module as well. Since
> the module already needs to be reset after some suspend/resume cycles,
> it is simple enough to reset it during every runtime suspend/resume.
> 
> Because the bus may be used by wakeup source IRQ threads, it needs to
> be functional as soon as IRQs are enabled. Thus, its system PM hooks
> need to run in the noirq phase.
> 
> Signed-off-by: Samuel Holland <samuel@...lland.org>

Gregory, what do you think?

> ---
>  drivers/i2c/busses/i2c-mv64xxx.c | 120 ++++++++++++++++++++-----------
>  1 file changed, 78 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
> index 5cfe70aedced..b03c344323d1 100644
> --- a/drivers/i2c/busses/i2c-mv64xxx.c
> +++ b/drivers/i2c/busses/i2c-mv64xxx.c
> @@ -18,6 +18,7 @@
>  #include <linux/mv643xx_i2c.h>
>  #include <linux/platform_device.h>
>  #include <linux/pinctrl/consumer.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/reset.h>
>  #include <linux/io.h>
>  #include <linux/of.h>
> @@ -717,6 +718,10 @@ mv64xxx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  	struct mv64xxx_i2c_data *drv_data = i2c_get_adapdata(adap);
>  	int rc, ret = num;
>  
> +	rc = pm_runtime_resume_and_get(&adap->dev);
> +	if (rc)
> +		return rc;
> +
>  	BUG_ON(drv_data->msgs != NULL);
>  	drv_data->msgs = msgs;
>  	drv_data->num_msgs = num;
> @@ -732,6 +737,9 @@ mv64xxx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  	drv_data->num_msgs = 0;
>  	drv_data->msgs = NULL;
>  
> +	pm_runtime_mark_last_busy(&adap->dev);
> +	pm_runtime_put_autosuspend(&adap->dev);
> +
>  	return ret;
>  }
>  
> @@ -828,7 +836,6 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
>  		rc = PTR_ERR(drv_data->rstc);
>  		goto out;
>  	}
> -	reset_control_deassert(drv_data->rstc);
>  
>  	/* Its not yet defined how timeouts will be specified in device tree.
>  	 * So hard code the value to 1 second.
> @@ -893,6 +900,32 @@ static int mv64xxx_i2c_init_recovery_info(struct mv64xxx_i2c_data *drv_data,
>  	return 0;
>  }
>  
> +static int
> +mv64xxx_i2c_runtime_suspend(struct device *dev)
> +{
> +	struct mv64xxx_i2c_data *drv_data = dev_get_drvdata(dev);
> +
> +	reset_control_assert(drv_data->rstc);
> +	clk_disable_unprepare(drv_data->reg_clk);
> +	clk_disable_unprepare(drv_data->clk);
> +
> +	return 0;
> +}
> +
> +static int
> +mv64xxx_i2c_runtime_resume(struct device *dev)
> +{
> +	struct mv64xxx_i2c_data *drv_data = dev_get_drvdata(dev);
> +
> +	clk_prepare_enable(drv_data->clk);
> +	clk_prepare_enable(drv_data->reg_clk);
> +	reset_control_reset(drv_data->rstc);
> +
> +	mv64xxx_i2c_hw_init(drv_data);
> +
> +	return 0;
> +}
> +
>  static int
>  mv64xxx_i2c_probe(struct platform_device *pd)
>  {
> @@ -920,18 +953,22 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>  
>  	/* Not all platforms have clocks */
>  	drv_data->clk = devm_clk_get(&pd->dev, NULL);
> -	if (PTR_ERR(drv_data->clk) == -EPROBE_DEFER)
> -		return -EPROBE_DEFER;
> -	if (!IS_ERR(drv_data->clk))
> -		clk_prepare_enable(drv_data->clk);
> +	if (IS_ERR(drv_data->clk)) {
> +		if (PTR_ERR(drv_data->clk) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +		drv_data->clk = NULL;
> +	}
>  
>  	drv_data->reg_clk = devm_clk_get(&pd->dev, "reg");
> -	if (PTR_ERR(drv_data->reg_clk) == -EPROBE_DEFER)
> -		return -EPROBE_DEFER;
> -	if (!IS_ERR(drv_data->reg_clk))
> -		clk_prepare_enable(drv_data->reg_clk);
> +	if (IS_ERR(drv_data->reg_clk)) {
> +		if (PTR_ERR(drv_data->reg_clk) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +		drv_data->reg_clk = NULL;
> +	}
>  
>  	drv_data->irq = platform_get_irq(pd, 0);
> +	if (drv_data->irq < 0)
> +		return drv_data->irq;
>  
>  	if (pdata) {
>  		drv_data->freq_m = pdata->freq_m;
> @@ -942,16 +979,12 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>  	} else if (pd->dev.of_node) {
>  		rc = mv64xxx_of_config(drv_data, &pd->dev);
>  		if (rc)
> -			goto exit_clk;
> -	}
> -	if (drv_data->irq < 0) {
> -		rc = drv_data->irq;
> -		goto exit_reset;
> +			return rc;
>  	}
>  
>  	rc = mv64xxx_i2c_init_recovery_info(drv_data, &pd->dev);
>  	if (rc == -EPROBE_DEFER)
> -		goto exit_reset;
> +		return rc;
>  
>  	drv_data->adapter.dev.parent = &pd->dev;
>  	drv_data->adapter.algo = &mv64xxx_i2c_algo;
> @@ -962,7 +995,14 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>  	platform_set_drvdata(pd, drv_data);
>  	i2c_set_adapdata(&drv_data->adapter, drv_data);
>  
> -	mv64xxx_i2c_hw_init(drv_data);
> +	pm_runtime_set_autosuspend_delay(&pd->dev, MSEC_PER_SEC);
> +	pm_runtime_use_autosuspend(&pd->dev);
> +	pm_runtime_enable(&pd->dev);
> +	if (!pm_runtime_enabled(&pd->dev)) {
> +		rc = mv64xxx_i2c_runtime_resume(&pd->dev);
> +		if (rc)
> +			goto exit_disable_pm;
> +	}
>  
>  	rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
>  			 MV64XXX_I2C_CTLR_NAME, drv_data);
> @@ -970,7 +1010,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>  		dev_err(&drv_data->adapter.dev,
>  			"mv64xxx: Can't register intr handler irq%d: %d\n",
>  			drv_data->irq, rc);
> -		goto exit_reset;
> +		goto exit_disable_pm;
>  	} else if ((rc = i2c_add_numbered_adapter(&drv_data->adapter)) != 0) {
>  		dev_err(&drv_data->adapter.dev,
>  			"mv64xxx: Can't add i2c adapter, rc: %d\n", -rc);
> @@ -981,54 +1021,50 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>  
>  exit_free_irq:
>  	free_irq(drv_data->irq, drv_data);
> -exit_reset:
> -	reset_control_assert(drv_data->rstc);
> -exit_clk:
> -	clk_disable_unprepare(drv_data->reg_clk);
> -	clk_disable_unprepare(drv_data->clk);
> +exit_disable_pm:
> +	pm_runtime_disable(&pd->dev);
> +	if (!pm_runtime_status_suspended(&pd->dev))
> +		mv64xxx_i2c_runtime_suspend(&pd->dev);
>  
>  	return rc;
>  }
>  
>  static int
> -mv64xxx_i2c_remove(struct platform_device *dev)
> +mv64xxx_i2c_remove(struct platform_device *pd)
>  {
> -	struct mv64xxx_i2c_data		*drv_data = platform_get_drvdata(dev);
> +	struct mv64xxx_i2c_data		*drv_data = platform_get_drvdata(pd);
>  
>  	i2c_del_adapter(&drv_data->adapter);
>  	free_irq(drv_data->irq, drv_data);
> -	reset_control_assert(drv_data->rstc);
> -	clk_disable_unprepare(drv_data->reg_clk);
> -	clk_disable_unprepare(drv_data->clk);
> +	pm_runtime_disable(&pd->dev);
> +	if (!pm_runtime_status_suspended(&pd->dev))
> +		mv64xxx_i2c_runtime_suspend(&pd->dev);
>  
>  	return 0;
>  }
>  
> -#ifdef CONFIG_PM
> -static int mv64xxx_i2c_resume(struct device *dev)
> +static void
> +mv64xxx_i2c_shutdown(struct platform_device *pd)
>  {
> -	struct mv64xxx_i2c_data *drv_data = dev_get_drvdata(dev);
> -
> -	mv64xxx_i2c_hw_init(drv_data);
> -
> -	return 0;
> +	pm_runtime_disable(&pd->dev);
> +	if (!pm_runtime_status_suspended(&pd->dev))
> +		mv64xxx_i2c_runtime_suspend(&pd->dev);
>  }
>  
> -static const struct dev_pm_ops mv64xxx_i2c_pm = {
> -	.resume = mv64xxx_i2c_resume,
> +static const struct dev_pm_ops mv64xxx_i2c_pm_ops = {
> +	SET_RUNTIME_PM_OPS(mv64xxx_i2c_runtime_suspend,
> +			   mv64xxx_i2c_runtime_resume, NULL)
> +	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> +				      pm_runtime_force_resume)
>  };
>  
> -#define mv64xxx_i2c_pm_ops (&mv64xxx_i2c_pm)
> -#else
> -#define mv64xxx_i2c_pm_ops NULL
> -#endif
> -
>  static struct platform_driver mv64xxx_i2c_driver = {
>  	.probe	= mv64xxx_i2c_probe,
>  	.remove	= mv64xxx_i2c_remove,
> +	.shutdown = mv64xxx_i2c_shutdown,
>  	.driver	= {
>  		.name	= MV64XXX_I2C_CTLR_NAME,
> -		.pm     = mv64xxx_i2c_pm_ops,
> +		.pm     = &mv64xxx_i2c_pm_ops,
>  		.of_match_table = mv64xxx_i2c_of_match_table,
>  	},
>  };
> -- 
> 2.26.2
> 

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