linux-kernel - Re: [PATCH v2 2/2] clk: imx95-blk-ctl: Save/restore registers when RPM routines are called

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Message-ID: <aJJoqZN4OOFS8hNT@lizhi-Precision-Tower-5810>
Date: Tue, 5 Aug 2025 16:25:13 -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 v2 2/2] clk: imx95-blk-ctl: Save/restore registers when
 RPM routines are called

On Mon, Aug 04, 2025 at 04:14:50PM +0300, Laurentiu Palcu wrote:
> When runtime PM is used for clock providers that are part of a power
> domain, the power domain supply is cut off during runtime suspend. This
> causes all BLK CTL registers belonging to that power domain to reset. To
> prevent this, save the state of the registers before entering suspend
> and restore them on resume. Additionally, disable the APB clock during
> suspend to minimize power consumption.
>
> Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....nxp.com>

Reviewed-by: Frank Li <Frank.Li@....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;
>  }
> --
> 2.49.0
>