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

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Message-ID: <Pine.LNX.4.44L0.1906051020540.1788-100000@iolanthe.rowland.org>
Date:   Wed, 5 Jun 2019 10:22:02 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Yinbo Zhu <yinbo.zhu@....com>
cc:     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@....com>
Subject: Re: [PATCH v6 4/5] usb: host: Stops USB controller init if PLL fails
 to lock

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:

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

>  		/* 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
>