linux-kernel - Re: [PATCH v2] extcon-intel-cht-wc: Don't reset USB data connection at probe

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Message-ID: <20190917132547.GA4226@jeknote.loshitsa1.net>
Date:   Tue, 17 Sep 2019 16:25:47 +0300
From:   Yauhen Kharuzhy <jekhor@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Hans de Goede <hdegoede@...hat.com>
Subject: Re: [PATCH v2] extcon-intel-cht-wc: Don't reset USB data connection
 at probe

On Tue, Sep 17, 2019 at 02:13:22PM +0300, Andy Shevchenko wrote:
> On Tue, Sep 17, 2019 at 12:15:36AM +0300, Yauhen Kharuzhy wrote:
> > Intel Cherry Trail Whiskey Cove extcon driver connect USB data lines to
> > PMIC at driver probing for further charger detection. This causes reset of
> > USB data sessions and removing all devices from bus. If system was
> > booted from Live CD or USB dongle, this makes system unusable.
> > 
> > Check if USB ID pin is floating and re-route data lines in this case
> > only, don't touch otherwise.
> 
> > +	ret = regmap_read(ext->regmap, CHT_WC_PWRSRC_STS, &pwrsrc_sts);
> > +	if (ret) {
> > +		dev_err(ext->dev, "Error reading pwrsrc status: %d\n", ret);
> > +		goto disable_sw_control;
> > +	}
> > +
> > +	id = cht_wc_extcon_get_id(ext, pwrsrc_sts);
> 
> We have second implementation of this. Would it make sense to split to some
> helper?

Do you mean the combination of regmap_read(...CHT_WC_PWRSRC_STS,
&pwrsrc_sts) with cht_wc_extcon_get_id()?

In the cht_wc_extcon_pwrsrc_event() function the pwrsrc_sts is checked
for other bits also, so separation of PWRSRC_STS read and id calculation
to one routine will cause non-clear function calls like as
get_powersrc_and_check_id(..., &powersrc_sts, &id) which is not looks
better than current code duplication. Or we need to spend some time for
refactoring and testing of cht_wc_extcon_pwrsrc_event() code.

> 
> > +	/* If no USB host or device connected, route D+ and D- to PMIC for
> > +	 * initial charger detection
> > +	 */
> 
> I'm not sure it's acceptable style of multi-line comment, but it's up to
> maintainer.
Argh, you are right, I fixed this in local copy but this is not
significant typo.

> 
> > +	if (id != INTEL_USB_ID_GND)
> > +		cht_wc_extcon_set_phymux(ext, MUX_SEL_PMIC);
> >  
> >  	/* Get initial state */
> >  	cht_wc_extcon_pwrsrc_event(ext);
> > -- 
> > 2.23.0.rc1
> > 
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

-- 
Yauhen Kharuzhy