linux-kernel - Re: [PATCH v2 02/10] clk: imx95-blk-ctl: Save/restore registers when RPM routines are called

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Message-ID: <lp3m4bahzbwvb6nfu2o6hsr5cux3y4rgdasbgba2jc774iei5a@plfpzihh7pen>
Date: Thu, 17 Jul 2025 15:23:38 +0300
From: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
To: Frank Li <Frank.li@....com>
Cc: imx@...ts.linux.dev, 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>, dri-devel@...ts.freedesktop.org, linux-clk@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/10] clk: imx95-blk-ctl: Save/restore registers when
 RPM routines are called

Hi Frank,

On Wed, Jul 16, 2025 at 02:29:01PM -0400, Frank Li wrote:
> On Wed, Jul 16, 2025 at 11:15:06AM +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.
> >
> > Also, fix the suspend/resume routines and make sure we disable/enable
> > the clock correctly.
> >
> > Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
> > ---
> >  drivers/clk/imx/clk-imx95-blk-ctl.c | 25 +++++++++++++------------
> >  1 file changed, 13 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..3f6bcc33bbe99 100644
> > --- a/drivers/clk/imx/clk-imx95-blk-ctl.c
> > +++ b/drivers/clk/imx/clk-imx95-blk-ctl.c
> > @@ -453,7 +453,9 @@ 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;
> >  }
> >
> > @@ -461,7 +463,10 @@ 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 clk_prepare_enable()'s return value!
> 
> > +	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> > +
> > +	return 0;
> >  }
> >  #endif
> >
> > @@ -469,17 +474,12 @@ 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;
> >  }
> > @@ -488,10 +488,11 @@ static int imx95_bc_resume(struct device *dev)
> >  {
> >  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> >
> > -	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);
> > +	clk_prepare_enable(bc->clk_apb);
> > +	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> >
> >  	return 0;
> >  }
> 
> Look like needn't imx95_bc_resume() and imx95_bc_suspend()
> 
> DEFINE_RUNTIME_DEV_PM_OPS() will use pm_runtime_force_suspend(), which
> do similar things with above logic.

As I said for v1, we cannot use DEFINE_RUNTIME_DEV_PM_OPS(). This driver
is used for various clock providers and RPM can be disabled for some of
them (see rpm_enabled flag in platform data). When RPM is disabled and
DEFINE_RUNTIME_DEV_PM_OPS() is used, pm_runtime_force_suspend() is
called, as you pointed out, and suspend() is never called.

Thanks,
Laurentiu

> 
> Frank
> 
> 
> > --
> > 2.34.1
> >