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 <3d1c7682-d163-4bcf-bd41-d7db0c8f61d1@wanadoo.fr>
In-Reply-To: <3d1c7682-d163-4bcf-bd41-d7db0c8f61d1@wanadoo.fr>
From: Anand Moon <linux.amoon@gmail.com>
Date: Sat, 2 Mar 2024 22:05:46 +0530
Message-ID: <CANAwSgR0aQ7nt1y5xknvVjHSnfvTaC8JZMLWurb8z2D0Oxg6Rw@mail.gmail.com>
Subject: Re: [PATCH v1 1/4] usb: ehci-exynos: Use devm_clk_get_enabled() helpers
To: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Alan Stern <stern@rowland.harvard.edu>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>, Alim Akhtar <alim.akhtar@samsung.com>, 
	linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, 
	linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org
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Hi Christophe,

On Sat, 2 Mar 2024 at 21:19, Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>
> Le 01/03/2024 =C3=A0 20:38, Anand Moon a =C3=A9crit :
> > The devm_clk_get_enabled() helpers:
> >      - call devm_clk_get()
> >      - call clk_prepare_enable() and register what is needed in order t=
o
> >       call clk_disable_unprepare() when needed, as a managed resource.
> >
> > This simplifies the code and avoids the calls to clk_disable_unprepare(=
).
> >
> > While at it, use dev_err_probe consistently, and use its return value
> > to return the error code.
> >
> > Signed-off-by: Anand Moon <linux.amoon@gmail.com>
> > ---
> >   drivers/usb/host/ehci-exynos.c | 30 +++++-------------------------
> >   1 file changed, 5 insertions(+), 25 deletions(-)
> >
> > diff --git a/drivers/usb/host/ehci-exynos.c b/drivers/usb/host/ehci-exy=
nos.c
> > index f644b131cc0b..05aa3d9c2a3b 100644
> > --- a/drivers/usb/host/ehci-exynos.c
> > +++ b/drivers/usb/host/ehci-exynos.c
> > @@ -159,19 +159,12 @@ static int exynos_ehci_probe(struct platform_devi=
ce *pdev)
> >
> >       err =3D exynos_ehci_get_phy(&pdev->dev, exynos_ehci);
> >       if (err)
> > -             goto fail_clk;
> > -
> > -     exynos_ehci->clk =3D devm_clk_get(&pdev->dev, "usbhost");
> > -
> > -     if (IS_ERR(exynos_ehci->clk)) {
> > -             dev_err(&pdev->dev, "Failed to get usbhost clock\n");
> > -             err =3D PTR_ERR(exynos_ehci->clk);
> > -             goto fail_clk;
> > -     }
> > +             goto fail_io;
> >
> > -     err =3D clk_prepare_enable(exynos_ehci->clk);
> > -     if (err)
> > -             goto fail_clk;
> > +     exynos_ehci->clk =3D devm_clk_get_enabled(&pdev->dev, "usbhost");
> > +     if (IS_ERR(exynos_ehci->clk))
> > +             return dev_err_probe(&pdev->dev, PTR_ERR(exynos_ehci->clk=
),
> > +                               "Failed to get usbhost clock\n");
> >
> >       hcd->regs =3D devm_platform_get_and_ioremap_resource(pdev, 0, &re=
s);
> >       if (IS_ERR(hcd->regs)) {
> > @@ -223,8 +216,6 @@ static int exynos_ehci_probe(struct platform_device=
 *pdev)
> >       exynos_ehci_phy_disable(&pdev->dev);
> >       pdev->dev.of_node =3D exynos_ehci->of_node;
> >   fail_io:
> > -     clk_disable_unprepare(exynos_ehci->clk);
> > -fail_clk:
> >       usb_put_hcd(hcd);
> >       return err;
> >   }
> > @@ -240,8 +231,6 @@ static void exynos_ehci_remove(struct platform_devi=
ce *pdev)
> >
> >       exynos_ehci_phy_disable(&pdev->dev);
> >
> > -     clk_disable_unprepare(exynos_ehci->clk);
> > -
> >       usb_put_hcd(hcd);
> >   }
> >
> > @@ -249,7 +238,6 @@ static void exynos_ehci_remove(struct platform_devi=
ce *pdev)
> >   static int exynos_ehci_suspend(struct device *dev)
> >   {
> >       struct usb_hcd *hcd =3D dev_get_drvdata(dev);
> > -     struct exynos_ehci_hcd *exynos_ehci =3D to_exynos_ehci(hcd);
> >
> >       bool do_wakeup =3D device_may_wakeup(dev);
> >       int rc;
> > @@ -260,25 +248,17 @@ static int exynos_ehci_suspend(struct device *dev=
)
> >
> >       exynos_ehci_phy_disable(dev);
> >
> > -     clk_disable_unprepare(exynos_ehci->clk);
>
> Hi,
>
> I don't think that removing clk_[en|dis]abble from the suspend and
> resume function is correct.
>
> The goal is to stop some hardware when the system is suspended, in order
> to save some power.
Yes correct,
>
> Why did you removed it?
>

devm_clk_get_enabled  function register callback for clk_prepare_enable
and clk_disable_unprepare, so when the clock resource is not used it should=
 get
disabled.

[0] https://elixir.bootlin.com/linux/latest/source/drivers/clk/clk-devres.c=
#L75

I have also tested with rtc suspend & resume and did not find any issue.

> CJ

Thanks
-Anand
>
> > -
> >       return rc;
> >   }
> >
> >   static int exynos_ehci_resume(struct device *dev)
> >   {
> >       struct usb_hcd *hcd =3D dev_get_drvdata(dev);
> > -     struct exynos_ehci_hcd *exynos_ehci =3D to_exynos_ehci(hcd);
> >       int ret;
> >
> > -     ret =3D clk_prepare_enable(exynos_ehci->clk);
> > -     if (ret)
> > -             return ret;
> > -
> >       ret =3D exynos_ehci_phy_enable(dev);
> >       if (ret) {
> >               dev_err(dev, "Failed to enable USB phy\n");
> > -             clk_disable_unprepare(exynos_ehci->clk);
> >               return ret;
> >       }
> >
>