linux-kernel - Re: [PATCH v2 1/2] PCI: j721e: Use devm_clk_get_optional

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Message-ID: <CANAwSgSTncwug+nUpm1pc2H8L0Abvumh8x09AW5p0nr8ufz-Yw@mail.gmail.com>
Date: Mon, 27 Oct 2025 12:11:57 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Siddharth Vadapalli <s-vadapalli@...com>
Cc: Vignesh Raghavendra <vigneshr@...com>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, 
	Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	"open list:PCI DRIVER FOR TI DRA7XX/J721E" <linux-omap@...r.kernel.org>, 
	"open list:PCI DRIVER FOR TI DRA7XX/J721E" <linux-pci@...r.kernel.org>, 
	"moderated list:PCI DRIVER FOR TI DRA7XX/J721E" <linux-arm-kernel@...ts.infradead.org>, 
	open list <linux-kernel@...r.kernel.org>, Markus Elfring <Markus.Elfring@....de>, 
	Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH v2 1/2] PCI: j721e: Use devm_clk_get_optional_enabled() to
 get the clock

Hi Siddharth,

On Mon, 27 Oct 2025 at 10:42, Siddharth Vadapalli <s-vadapalli@...com> wrote:
>
> On Sat, 2025-10-25 at 14:07 +0530, Anand Moon wrote:
> > Hi Siddharth,
> >
> > Thanks for your review comments,
> >
> > On Sat, 25 Oct 2025 at 13:20, Siddharth Vadapalli <s-vadapalli@...com> wrote:
> > >
> > > On Sat, 2025-10-25 at 13:13 +0530, Anand Moon wrote:
> > > > Use devm_clk_get_optional_enabled() helper instead of calling
> > > > devm_clk_get_optional() and then clk_prepare_enable(). It simplifies
> > > > the clk_prepare_enable() and clk_disable_unprepare() with proper error
> > > > handling and makes the code more compact.
> > > > The result of devm_clk_get_optional_enabled() is now assigned directly
> > > > to pcie->refclk. This removes a superfluous local clk variable,
> > > > improving code readability and compactness. The functionality
> > > > remains unchanged, but the code is now more streamlined.
> > > >
> > > > Cc: Siddharth Vadapalli <s-vadapalli@...com>
> > > > Signed-off-by: Anand Moon <linux.amoon@...il.com>
> > > > ---
> > > > v2: Rephase the commit message and use proper error pointer
> > > >     PTR_ERR(pcie->refclk) to return error.
> > > > v1: Drop explicit clk_disable_unprepare as it handled by
> > > >     devm_clk_get_optional_enabled, Since devm_clk_get_optional_enabled
> > > >     internally manages clk_prepare_enable and clk_disable_unprepare
> > > >     as part of its lifecycle, the explicit call to clk_disable_unprepare
> > > >     is redundant and can be safely removed.
> > > > ---
> > > >  drivers/pci/controller/cadence/pci-j721e.c | 21 +++++----------------
> > > >  1 file changed, 5 insertions(+), 16 deletions(-)
> > > >
> > > > diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
> > > > index 5bc5ab20aa6d..b678f7d48206 100644
> > > > --- a/drivers/pci/controller/cadence/pci-j721e.c
> > > > +++ b/drivers/pci/controller/cadence/pci-j721e.c
> > >
> > > [TRIMMED]
> > >
> > > > @@ -692,7 +682,6 @@ static int j721e_pcie_suspend_noirq(struct device *dev)
> > > >
> > > >       if (pcie->mode == PCI_MODE_RC) {
> > > >               gpiod_set_value_cansleep(pcie->reset_gpio, 0);
> > > > -             clk_disable_unprepare(pcie->refclk);
> > >
> > > j721e_pcie_resume_noirq() contains clk_enable_prepare().
> > Ok I will drop the clk_prepare_enable and clk_disable_unprepare in
> > this function?
>
> The clock needs to be disabled on Suspend and enabled on Resume.
>
> The reasoning behind replacing:
> devm_clk_get_optional()  + clk_prepare_enable()
> with:
> devm_clk_get_optional_enabled()
> is clear to me, but the removal of the 'clk_disable_unprepare()' on the
> Suspend path isn't.
>
> Removing 'clk_disable_unprepare()' in the driver's remove path makes sense
> because the
> devm() API will automatically disable and unprepare the clock when the
> device is "unbound".
> However, to the best of my understanding, the device is not "unbound"
> during Suspend.
Thanks for clarifying my doubt. That part makes sense.
> Can you clarify why 'clk_disable_unprepare()' should be removed in
> j721e_pcie_suspend_noirq()?
It happened by mistake.
> Regards,
> Siddharth.
Thanks
-Anand