linux-kernel - Re: [PATCH v1 1/4] usb: ehci-exynos: Use devm_clk_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANAwSgR0aQ7nt1y5xknvVjHSnfvTaC8JZMLWurb8z2D0Oxg6Rw@mail.gmail.com>
Date: Sat, 2 Mar 2024 22:05:46 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Alan Stern <stern@...land.harvard.edu>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Alim Akhtar <alim.akhtar@...sung.com>, 
	linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/4] usb: ehci-exynos: Use devm_clk_get_enabled() helpers

Hi Christophe,

On Sat, 2 Mar 2024 at 21:19, Christophe JAILLET
<christophe.jaillet@...adoo.fr> wrote:
>
> Le 01/03/2024 à 20:38, Anand Moon a écrit :
> > The devm_clk_get_enabled() helpers:
> >      - call devm_clk_get()
> >      - call clk_prepare_enable() and register what is needed in order to
> >       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@...il.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-exynos.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_device *pdev)
> >
> >       err = exynos_ehci_get_phy(&pdev->dev, exynos_ehci);
> >       if (err)
> > -             goto fail_clk;
> > -
> > -     exynos_ehci->clk = devm_clk_get(&pdev->dev, "usbhost");
> > -
> > -     if (IS_ERR(exynos_ehci->clk)) {
> > -             dev_err(&pdev->dev, "Failed to get usbhost clock\n");
> > -             err = PTR_ERR(exynos_ehci->clk);
> > -             goto fail_clk;
> > -     }
> > +             goto fail_io;
> >
> > -     err = clk_prepare_enable(exynos_ehci->clk);
> > -     if (err)
> > -             goto fail_clk;
> > +     exynos_ehci->clk = 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 = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> >       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 = 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_device *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_device *pdev)
> >   static int exynos_ehci_suspend(struct device *dev)
> >   {
> >       struct usb_hcd *hcd = dev_get_drvdata(dev);
> > -     struct exynos_ehci_hcd *exynos_ehci = to_exynos_ehci(hcd);
> >
> >       bool do_wakeup = 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 = dev_get_drvdata(dev);
> > -     struct exynos_ehci_hcd *exynos_ehci = to_exynos_ehci(hcd);
> >       int ret;
> >
> > -     ret = clk_prepare_enable(exynos_ehci->clk);
> > -     if (ret)
> > -             return ret;
> > -
> >       ret = exynos_ehci_phy_enable(dev);
> >       if (ret) {
> >               dev_err(dev, "Failed to enable USB phy\n");
> > -             clk_disable_unprepare(exynos_ehci->clk);
> >               return ret;
> >       }
> >
>