Re: [PATCH 1/8] clk: imx95-blk-ctl: Cache registers when RPM routines are called

[Frank Li <Frank.li@nxp.com>]

Subject:
save and store registers at suspend()/resume() function

On Wed, Jul 09, 2025 at 03:23:20PM +0300, Laurentiu Palcu wrote:
> If runtime PM is used for the clock providers and they're part of a
> power domain, then the power domain supply will be cut off when runtime
> suspended. That means all BLK CTL registers belonging to that power
> domain will be reset. Hence, the clock settings will revert to default
> values messing up the consumer clock settings.

Needn't "hence ..."

Save/restore register value at suspend/resume functions to fix this problem.

>
> Also, fix the suspend/resume routines as well, as the clock was left ON
> when going to suspend.

Do you means fix the problem clock left ON after suspend?

Pomain cut off, why clock can left on?

>
> Fixes: 5224b189462f ("clk: imx: add i.MX95 BLK CTL clk driver")
> Signed-off-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
> ---
>  drivers/clk/imx/clk-imx95-blk-ctl.c | 55 ++++++++++++++++++-----------
>  1 file changed, 34 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/clk/imx/clk-imx95-blk-ctl.c b/drivers/clk/imx/clk-imx95-blk-ctl.c
> index 7e88877a62451..7f9bbca517284 100644
> --- a/drivers/clk/imx/clk-imx95-blk-ctl.c
> +++ b/drivers/clk/imx/clk-imx95-blk-ctl.c
> @@ -448,12 +448,36 @@ static int imx95_bc_probe(struct platform_device *pdev)
>  	return ret;
>  }
>
> +static void __maybe_unused imx95_bc_save_reg(struct imx95_blk_ctl *bc)
> +{
> +	const struct imx95_blk_ctl_dev_data *bc_data;
> +
> +	bc_data = of_device_get_match_data(bc->dev);
> +	if (!bc_data)
> +		return;
> +
> +	bc->clk_reg_restore = readl(bc->base + bc_data->clk_reg_offset);
> +}
> +
> +static void __maybe_unused imx95_bc_restore_reg(struct imx95_blk_ctl *bc)
> +{
> +	const struct imx95_blk_ctl_dev_data *bc_data;
> +
> +	bc_data = of_device_get_match_data(bc->dev);

Generally, bc_data should in imx95_blk_ctl_dev_data and set once at probe.

So imx95_bc_save_reg() and imx95_bc_restore_reg() will be simpfied.

> +	if (!bc_data)
> +		return;
> +
> +	writel(bc->clk_reg_restore, bc->base + bc_data->clk_reg_offset);
> +}
> +
>  #ifdef CONFIG_PM
>  static int imx95_bc_runtime_suspend(struct device *dev)
>  {
>  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
>
> +	imx95_bc_save_reg(bc);

this help function just one line. direct use

writel(bc->clk_reg_restore, bc->base + bc->bc_data->clk_reg_offset);

>  	clk_disable_unprepare(bc->clk_apb);
> +
>  	return 0;
>  }
>
> @@ -461,7 +485,10 @@ static int imx95_bc_runtime_resume(struct device *dev)
>  {
>  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
>
> -	return clk_prepare_enable(bc->clk_apb);
> +	clk_prepare_enable(bc->clk_apb);

Need check ret value;

> +	imx95_bc_restore_reg(bc);
> +
> +	return 0;
>  }
>  #endif
>
> @@ -469,22 +496,12 @@ static int imx95_bc_runtime_resume(struct device *dev)
>  static int imx95_bc_suspend(struct device *dev)
>  {
>  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> -	const struct imx95_blk_ctl_dev_data *bc_data;
> -	int ret;
>
> -	bc_data = of_device_get_match_data(dev);
> -	if (!bc_data)
> +	if (pm_runtime_suspended(dev))
>  		return 0;
>
> -	if (bc_data->rpm_enabled) {
> -		ret = pm_runtime_get_sync(bc->dev);
> -		if (ret < 0) {
> -			pm_runtime_put_noidle(bc->dev);
> -			return ret;
> -		}
> -	}
> -
> -	bc->clk_reg_restore = readl(bc->base + bc_data->clk_reg_offset);
> +	imx95_bc_save_reg(bc);
> +	clk_disable_unprepare(bc->clk_apb);
>
>  	return 0;
>  }
> @@ -492,16 +509,12 @@ static int imx95_bc_suspend(struct device *dev)
>  static int imx95_bc_resume(struct device *dev)
>  {
>  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> -	const struct imx95_blk_ctl_dev_data *bc_data;
>
> -	bc_data = of_device_get_match_data(dev);
> -	if (!bc_data)
> +	if (pm_runtime_suspended(dev))
>  		return 0;
>
> -	writel(bc->clk_reg_restore, bc->base + bc_data->clk_reg_offset);
> -
> -	if (bc_data->rpm_enabled)
> -		pm_runtime_put(bc->dev);
> +	clk_prepare_enable(bc->clk_apb);
> +	imx95_bc_restore_reg(bc);
>
>  	return 0;
>  }

look like imx95_bc_suspend(resume) is simple enough

Can you use DEFINE_RUNTIME_DEV_PM_OPS?

Frank

> --
> 2.46.1
>