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

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Date:   Mon, 16 Sep 2019 22:12:14 +0300
From:   Yauhen Kharuzhy <jekhor@...il.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH] extcon-intel-cht-wc: Don't reset USB data connection at
 probe

On Mon, Aug 12, 2019 at 07:18:45PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 09-08-19 17:11, Yauhen Kharuzhy wrote:
> > On Fri, Aug 09, 2019 at 01:06:01PM +0200, Hans de Goede wrote:
> > > Hi,
> > > 
> > > On 8/9/19 12:01 AM, 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.
> > > > 
> > > > Signed-off-by: Yauhen Kharuzhy <jekhor@...il.com>
> > > > ---
> > > >    drivers/extcon/extcon-intel-cht-wc.c | 16 ++++++++++++++--
> > > >    1 file changed, 14 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/extcon/extcon-intel-cht-wc.c b/drivers/extcon/extcon-intel-cht-wc.c
> > > > index 9d32150e68db..3ae573e93e6e 100644
> > > > --- a/drivers/extcon/extcon-intel-cht-wc.c
> > > > +++ b/drivers/extcon/extcon-intel-cht-wc.c
> > > > @@ -338,6 +338,7 @@ static int cht_wc_extcon_probe(struct platform_device *pdev)
> > > >    	struct intel_soc_pmic *pmic = dev_get_drvdata(pdev->dev.parent);
> > > >    	struct cht_wc_extcon_data *ext;
> > > >    	unsigned long mask = ~(CHT_WC_PWRSRC_VBUS | CHT_WC_PWRSRC_USBID_MASK);
> > > > +	int pwrsrc_sts, id;
> > > >    	int irq, ret;
> > > >    	irq = platform_get_irq(pdev, 0);
> > > > @@ -387,8 +388,19 @@ static int cht_wc_extcon_probe(struct platform_device *pdev)
> > > >    		goto disable_sw_control;
> > > >    	}
> > > > -	/* Route D+ and D- to PMIC for initial charger detection */
> > > > -	cht_wc_extcon_set_phymux(ext, MUX_SEL_PMIC);
> > > > +	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);
> > > > +
> > > > +	/* If no USB host or device connected, route D+ and D- to PMIC for
> > > > +	 * initial charger detection
> > > > +	 */
> > > > +	if (id == INTEL_USB_ID_FLOAT)
> > > > +		cht_wc_extcon_set_phymux(ext, MUX_SEL_PMIC);
> > > 
> > > The check here should be != INTEL_USB_ID_GND, when we are connected as
> > > device we are charging from the host we are connected to and the port
> > > we are connected to may be a CDP (charging downstream port) instead of
> > > a SDP (standard downstream port) allowing us to charge at 1.5A instead
> > > of 0.5A, also != INTEL_USB_ID_GND matches the condition used in
> > > cht_wc_extcon_pwrsrc_event to determine if we should continue with
> > > charger detection there.
> > 
> > Actually it should be checked as ((id != INTEL_USB_ID_GND) && (id !=
> > INTEL_USB_RID_A)), to not interrupt connection if ACA used and our host
> > is OTG A device (for example, if LiveCD boots from USB flash inserted
> > into an ACA USB hub).
> 
> Right, except that cht_wc_extcon_get_id never returns INTEL_USB_RID_A,
> so checking for that would be superfluous and also would be inconsistent
> with what cht_wc_extcon_pwrsrc_event is doing, so for now please just test
> for != INTEL_USB_ID_GND, if cht_wc_extcon_get_id ever starts supporting
> RID_A then we should fix both cht_wc_extcon_pwrsrc_event and you new check
> at that time.
> 
> Hmm, I now see that cht_wc_extcon_get_id currently only reports one of:
> INTEL_USB_ID_GND or INTEL_USB_ID_FLOAT so == INTEL_USB_ID_FLOAT is
> equivalent to != INTEL_USB_ID_GND still please check for 1= INTEL_USB_ID_GND
> as that is what cht_wc_extcon_pwrsrc_event is doing.
> 
> > > Like your other patch I will try to give this one a  test-run tomorrow.
> 
> I've given this patch a test-run today and I can confirm that BC1.2 charger
> detection still works fine on my device using this driver.

OK.


-- 
Yauhen Kharuzhy