linux-kernel - Re: [PATCH 2/2] clk: imx95-blk-ctl: Save/restore registers when RPM routines are called

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Message-ID: <aIpHEugNppI2C0/q@lizhi-Precision-Tower-5810>
Date: Wed, 30 Jul 2025 12:23:46 -0400
From: Frank Li <Frank.li@....com>
To: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
Cc: Abel Vesa <abelvesa@...nel.org>, Peng Fan <peng.fan@....com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-clk@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] clk: imx95-blk-ctl: Save/restore registers when RPM
 routines are called

On Wed, Jul 30, 2025 at 03:59:31PM +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. Save the registers, then, before entering suspend
> and restore them in resume.

Save the registers before entering suspend, then restore them in resume.

>
> Also, fix the suspend/resume routines and make sure we disable/enable
> the clock correctly.

Check runtime pm status in suspend/resume routines to make sure
disable/enable clock correctly.

>
> Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
> ---
>  drivers/clk/imx/clk-imx95-blk-ctl.c | 33 ++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/clk/imx/clk-imx95-blk-ctl.c b/drivers/clk/imx/clk-imx95-blk-ctl.c
> index c72debaf3a60b..56bed44719954 100644
> --- a/drivers/clk/imx/clk-imx95-blk-ctl.c
> +++ b/drivers/clk/imx/clk-imx95-blk-ctl.c
> @@ -453,15 +453,24 @@ static int imx95_bc_runtime_suspend(struct device *dev)
>  {
>  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
>
> +	bc->clk_reg_restore = readl(bc->base + bc->pdata->clk_reg_offset);
>  	clk_disable_unprepare(bc->clk_apb);
> +
>  	return 0;
>  }
>
>  static int imx95_bc_runtime_resume(struct device *dev)
>  {
>  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> +	int ret;
>
> -	return clk_prepare_enable(bc->clk_apb);
> +	ret = clk_prepare_enable(bc->clk_apb);
> +	if (ret)
> +		return ret;
> +
> +	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> +
> +	return 0;
>  }
>  #endif
>
> @@ -469,17 +478,12 @@ 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);
> -	int ret;
>
> -	if (bc->pdata->rpm_enabled) {
> -		ret = pm_runtime_get_sync(bc->dev);
> -		if (ret < 0) {
> -			pm_runtime_put_noidle(bc->dev);
> -			return ret;
> -		}
> -	}
> +	if (pm_runtime_suspended(dev))
> +		return 0;
>
>  	bc->clk_reg_restore = readl(bc->base + bc->pdata->clk_reg_offset);
> +	clk_disable_unprepare(bc->clk_apb);
>
>  	return 0;
>  }
> @@ -487,11 +491,16 @@ 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);
> +	int ret;
>
> -	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> +	if (pm_runtime_suspended(dev))
> +		return 0;
>
> -	if (bc->pdata->rpm_enabled)
> -		pm_runtime_put(bc->dev);
> +	ret = clk_prepare_enable(bc->clk_apb);
> +	if (ret)
> +		return ret;
> +
> +	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
>
>  	return 0;
>  }
> --
> 2.46.1
>