linux-kernel - Re: [PATCH v1 5/8] usb: chipidea: tegra: Support host mode

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Message-ID: <f5571caf-9a17-3b03-14fa-dc988b10747a@gmail.com>
Date:   Wed, 16 Dec 2020 12:22:22 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Peter Chen <peter.chen@....com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Felipe Balbi <balbi@...nel.org>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Peter Geis <pgwipeout@...il.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 5/8] usb: chipidea: tegra: Support host mode

16.12.2020 12:07, Dmitry Osipenko пишет:
>>>  static int ehci_ci_portpower(struct usb_hcd *hcd, int portnum, bool enable)
>>>  {
>>>  	struct ehci_hcd *ehci = hcd_to_ehci(hcd);
>>> @@ -160,14 +166,14 @@ static int host_start(struct ci_hdrc *ci)
>>>  		pinctrl_select_state(ci->platdata->pctl,
>>>  				     ci->platdata->pins_host);
>>>  
>>> +	ci->hcd = hcd;
>>> +
>>>  	ret = usb_add_hcd(hcd, 0, 0);
>>>  	if (ret) {
>>>  		goto disable_reg;
>>>  	} else {
>>>  		struct usb_otg *otg = &ci->otg;
>>>  
>>> -		ci->hcd = hcd;
>>> -
>> Why this changed?
> The ci->hcd is used by tegra_usb_notify_event() to handle reset event
> and the reset happens once usb_add_hcd() is invoked.  Hence we need to
> pre-assign the hcd pointer, otherwise there will be a NULL dereference.

Actually, not a NULL dereference, but the reset will be skipped since we
check whether ci->hcd is NULL in the tegra's reset handler.