linux-kernel - RE: [EXT] Re: [PATCH v6 4/5] usb: host: Stops USB controller init if PLL fails to lock

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Date:   Thu, 6 Jun 2019 06:35:14 +0000
From:   Yinbo Zhu <yinbo.zhu@....com>
To:     Alan Stern <stern@...land.harvard.edu>
CC:     Xiaobo Xie <xiaobo.xie@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ramneek Mehresh <ramneek.mehresh@...escale.com>,
        Nikhil Badola <nikhil.badola@...escale.com>,
        Ran Wang <ran.wang_1@....com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jiafei Pan <jiafei.pan@....com>
Subject: RE: [EXT] Re: [PATCH v6 4/5] usb: host: Stops USB controller init if
 PLL fails to lock



> -----Original Message-----
> From: Alan Stern [mailto:stern@...land.harvard.edu]
> Sent: 2019年6月5日 22:22
> To: Yinbo Zhu <yinbo.zhu@....com>
> Cc: Xiaobo Xie <xiaobo.xie@....com>; Greg Kroah-Hartman
> <gregkh@...uxfoundation.org>; Ramneek Mehresh
> <ramneek.mehresh@...escale.com>; Nikhil Badola
> <nikhil.badola@...escale.com>; Ran Wang <ran.wang_1@....com>;
> linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org; Jiafei Pan
> <jiafei.pan@....com>
> Subject: [EXT] Re: [PATCH v6 4/5] usb: host: Stops USB controller init if PLL fails to
> lock
> 
> Caution: EXT Email
> 
> On Wed, 5 Jun 2019, Yinbo Zhu wrote:
> 
> > From: Ramneek Mehresh <ramneek.mehresh@...escale.com>
> >
> > USB erratum-A006918 workaround tries to start internal PHY inside
> > uboot (when PLL fails to lock). However, if the workaround also fails,
> > then USB initialization is also stopped inside Linux.
> > Erratum-A006918 workaround failure creates "fsl,erratum_a006918"
> > node in device-tree. Presence of this node in device-tree is used to
> > stop USB controller initialization in Linux
> >
> > Signed-off-by: Ramneek Mehresh <ramneek.mehresh@...escale.com>
> > Signed-off-by: Suresh Gupta <suresh.gupta@...escale.com>
> > Signed-off-by: Yinbo Zhu <yinbo.zhu@....com>
> > ---
> > Change in v6:
> >               add a "Fall through" comment
> >
> >  drivers/usb/host/ehci-fsl.c      | 10 +++++++++-
> >  drivers/usb/host/fsl-mph-dr-of.c |  3 ++-
> >  2 files changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/host/ehci-fsl.c b/drivers/usb/host/ehci-fsl.c
> > index 8f3bf3efb038..86ae37086a74 100644
> > --- a/drivers/usb/host/ehci-fsl.c
> > +++ b/drivers/usb/host/ehci-fsl.c
> > @@ -234,8 +234,16 @@ static int ehci_fsl_setup_phy(struct usb_hcd *hcd,
> >               break;
> >       case FSL_USB2_PHY_UTMI_WIDE:
> >               portsc |= PORT_PTS_PTW;
> > -             /* fall through */
> >       case FSL_USB2_PHY_UTMI:
> > +             /* Presence of this node "has_fsl_erratum_a006918"
> > +              * in device-tree is used to stop USB controller
> > +              * initialization in Linux
> > +              */
> > +             if (pdata->has_fsl_erratum_a006918) {
> > +                     dev_warn(dev, "USB PHY clock invalid\n");
> > +                     return -EINVAL;
> > +             }
> > +
> >       case FSL_USB2_PHY_UTMI_DUAL:
> 
> 
> You need to add a "Fall through" comment between these two cases.
> >       case FSL_USB2_PHY_UTMI_DUAL:
> >               /* PHY_CLK_VALID bit is de-featured from all controller
> >                * versions below 2.4 and is to be checked only for
> 
> Alan Stern
> Hi Alan Stern,
>
> Your meaning is to remove "/* fall through*/" or add the erratum commont replace "/* fall through*/"
>
> Regards,
> Yinbo
> This is bad.  You got rid of a "fall through" comment that was needed, and you
> failed to add another one where it was needed.
> 
> Alan Stern
I don't get your meaning.
Yinbo
> 
> >               /* PHY_CLK_VALID bit is de-featured from all controller
> >                * versions below 2.4 and is to be checked only for diff
> > --git a/drivers/usb/host/fsl-mph-dr-of.c
> > b/drivers/usb/host/fsl-mph-dr-of.c
> > index 4f8b8a08c914..762b97600ab0 100644
> > --- a/drivers/usb/host/fsl-mph-dr-of.c
> > +++ b/drivers/usb/host/fsl-mph-dr-of.c
> > @@ -224,13 +224,14 @@ static int fsl_usb2_mph_dr_of_probe(struct
> platform_device *ofdev)
> >               of_property_read_bool(np, "fsl,usb-erratum-a005275");
> >       pdata->has_fsl_erratum_a005697 =
> >               of_property_read_bool(np, "fsl,usb_erratum-a005697");
> > +     pdata->has_fsl_erratum_a006918 =
> > +             of_property_read_bool(np, "fsl,usb_erratum-a006918");
> >
> >       if (of_get_property(np, "fsl,usb_erratum_14", NULL))
> >               pdata->has_fsl_erratum_14 = 1;
> >       else
> >               pdata->has_fsl_erratum_14 = 0;
> >
> > -
> >       /*
> >        * Determine whether phy_clk_valid needs to be checked
> >        * by reading property in device tree
> >