linux-kernel - Re: [PATCH v3] PCI: armada8k: change to use devm_clk_get

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Message-ID: <CANAwSgRi4KUoxjtNn87PRHXVJ2rxwqcxo96LCtOCgbOD+RNWQQ@mail.gmail.com>
Date: Sat, 31 Aug 2024 09:07:20 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Wu Bo <wubo.oduw@...il.com>
Cc: Wu Bo <bo.wu@...o.com>, linux-kernel@...r.kernel.org, 
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kw@...ux.com>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Rob Herring <robh@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] PCI: armada8k: change to use devm_clk_get_enabled() helper

Hi Wu Bo,

On Sat, 31 Aug 2024 at 05:36, Wu Bo <wubo.oduw@...il.com> wrote:
>
> On 2024/8/27 14:44, Anand Moon wrote:
> > Hi Wu Bo,
> >
> > On Tue, 27 Aug 2024 at 07:55, Wu Bo <bo.wu@...o.com> wrote:
> >> Use devm_clk_get_enabled() instead of devm_clk_get() to make the code
> >> cleaner and avoid calling clk_disable_unprepare()
> >>
> >> Signed-off-by: Wu Bo <bo.wu@...o.com>
> >> ---
> >>   drivers/pci/controller/dwc/pcie-armada8k.c | 36 ++++++++--------------
> >>   1 file changed, 13 insertions(+), 23 deletions(-)
> >>
> >> diff --git a/drivers/pci/controller/dwc/pcie-armada8k.c b/drivers/pci/controller/dwc/pcie-armada8k.c
> >> index b5c599ccaacf..e7ef6c2641b8 100644
> >> --- a/drivers/pci/controller/dwc/pcie-armada8k.c
> >> +++ b/drivers/pci/controller/dwc/pcie-armada8k.c
> >> @@ -284,23 +284,17 @@ static int armada8k_pcie_probe(struct platform_device *pdev)
> >>
> >>          pcie->pci = pci;
> >>
> >> -       pcie->clk = devm_clk_get(dev, NULL);
> >> +       pcie->clk = devm_clk_get_enabled(dev, NULL);
> >>          if (IS_ERR(pcie->clk))
> >> -               return PTR_ERR(pcie->clk);
> >> -
> >> -       ret = clk_prepare_enable(pcie->clk);
> >> -       if (ret)
> >> -               return ret;
> >> -
> >> -       pcie->clk_reg = devm_clk_get(dev, "reg");
> >> -       if (pcie->clk_reg == ERR_PTR(-EPROBE_DEFER)) {
> >> -               ret = -EPROBE_DEFER;
> >> -               goto fail;
> >> -       }
>
> I don't know much about this device. But from the code here, its
> previous logic is that the function will only return when the error code
> is EPROBE_DEFER, and other errors will continue to execute.
>
> So I followed the previous logic, is it correct？

We probably get -EPROBE_DEFER since the clk is not getting enabled during probe.
and we defer the initialization by returning the error. using
dev_err_probe function.
.
We don't need to recheck for EPROBE_DEFER, again it's handled in
dev_err_probe see below.

[1] https://elixir.bootlin.com/linux/v6.10.7/source/drivers/base/core.c#L5018

Thanks
-Anand
>
> >> -       if (!IS_ERR(pcie->clk_reg)) {
> >> -               ret = clk_prepare_enable(pcie->clk_reg);
> >> -               if (ret)
> >> -                       goto fail_clkreg;
> >> +               return dev_err_probe(dev, PTR_ERR(pcie->clk),
> >> +                               "could not enable clk\n");
> >> +
> >> +       pcie->clk_reg = devm_clk_get_enabled(dev, "reg");
> >> +       if (IS_ERR(pcie->clk_reg)) {
> >> +               ret = dev_err_probe(dev, PTR_ERR(pcie->clk_reg),
> >> +                               "could not enable reg clk\n");
> >> +               if (ret == -EPROBE_DEFER)
> >> +                       goto out;
> > You can drop this check as dev_err_probe handle this inside
> > It will defer the enabling of clock.
> >>          }
> >>
> >>          /* Get the dw-pcie unit configuration/control registers base. */
> >> @@ -308,12 +302,12 @@ static int armada8k_pcie_probe(struct platform_device *pdev)
> >>          pci->dbi_base = devm_pci_remap_cfg_resource(dev, base);
> >>          if (IS_ERR(pci->dbi_base)) {
> >>                  ret = PTR_ERR(pci->dbi_base);
> >> -               goto fail_clkreg;
> >> +               goto out;
> >>          }
> >>
> >>          ret = armada8k_pcie_setup_phys(pcie);
> >>          if (ret)
> >> -               goto fail_clkreg;
> >> +               goto out;
> >>
> >>          platform_set_drvdata(pdev, pcie);
> >>
> >> @@ -325,11 +319,7 @@ static int armada8k_pcie_probe(struct platform_device *pdev)
> >>
> >>   disable_phy:
> >>          armada8k_pcie_disable_phys(pcie);
> >> -fail_clkreg:
> >> -       clk_disable_unprepare(pcie->clk_reg);
> >> -fail:
> >> -       clk_disable_unprepare(pcie->clk);
> >> -
> >> +out:
> >>          return ret;
> >>   }
> >>
> > Thanks
> > -Anand
> >> --
> >> 2.25.1
> >>
> >>