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Message-ID: <uqkh54tsbv7pyfgfwm6i22xsnevzokyrv253bju5hbhypbckfl@qy7aqlaylp3w>
Date: Tue, 15 Jul 2025 15:03:57 +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,
Abel Vesa <abel.vesa@...aro.org>, linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] clk: imx95-blk-ctl: Cache registers when RPM
routines are called
Hi Frank,
On Fri, Jul 11, 2025 at 12:03:22AM -0400, Frank Li wrote:
> 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?
I'm referring to the BLK_CTL clock supplier here. We need to call
clk_disable_unprepare() in suspend() too.
>
> >
> > Fixes: 5224b189462f ("clk: imx: add i.MX95 BLK CTL clk driver")
> > Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....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.
Agree, I'll do this in a separate patch though for easier review.
>
> > + 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);
ok.
>
> > 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?
Not really. Some clocks provided by BLK_CTL use RPM, others don't. If we
use DEFINE_RUNTIME_DEV_PM_OPS, then suspend()/resume() routines will
never be called when rpm_enable is false.
Thanks,
Laurentiu
>
> Frank
>
> > --
> > 2.46.1
> >
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