Re: [PATCH] usb: hub: fix state change check for not powercycled ports

[Michael Grzeschik <mgr@pengutronix.de>]

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Hi!

On Thu, Feb 11, 2021 at 01:03:54PM +0100, Ahmad Fatoum wrote:
>Hello,
>
>On 18.01.21 20:09, Michael Grzeschik wrote:
>> Since we don't power cycle the ports on start since patch "19bb0b2a usb:
>> hub: Do not power-cycle usb devices on init" it is possible that the
>> device on this port is already active from a previous enumeration. This
>> way barebox will never get any change in USB_PORT_STAT_C_CONNECTION bit
>> change.
>>
>> Although the device will probably still work fine after the following
>> port reset, the current code will always miss reenumerating these still
>> plugged devices. This patch fixes this by ignoring the check for
>> STAT_C_CONNECTION bit and only go for USB_PORT_STAT_CONNECTION which
>> should be enough.
>
>This breaks USB enumeration for me on an i.MX6Q. The USB flash driver behind
>the hub is detected twice, which barebox doesn't like at all:
>
>barebox@Embest MarS Board i.MX6Dual:/ usb -s
>usb: USB: scanning bus for devices...
>usb1: Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
>usb1-0: Bus 001 Device 002: ID 1a40:0101 USB 2.0 Hub [MTT]
>usb1-0-1: Bus 001 Device 003: ID 058f:6387 Mass Storage
>Using index 0 for the new disk
>usb1-0-1: Bus 001 Device 004: ID 058f:6387 Mass Storage
>ERROR: register_device: already registered usb1-0-1
>ERROR: usb1-0-1: Failed to register device: Invalid argument
>usb: 3 USB Device(s) found
>Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
>Bus 001 Device 002: ID 1a40:0101 USB 2.0 Hub [MTT]
>Bus 001 Device 003: ID 058f:6387 Mass Storage
>
>This seems to corrupt some internal barebox state as reading
>/dev/disk0.0 will hang. Reading /dev/disk0 is fine however.
>
>With this patch reverted it however works:
>
>usb: USB: scanning bus for devices...
>usb1: Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
>usb1-0: Bus 001 Device 002: ID 1a40:0101 USB 2.0 Hub [MTT]
>usb1-0-1: Bus 001 Device 003: ID 058f:6387 Mass Storage
>Using index 0 for the new disk
>usb: 3 USB Device(s) found
>Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
>Bus 001 Device 002: ID 1a40:0101 USB 2.0 Hub [MTT]
>Bus 001 Device 003: ID 058f:6387 Mass Storage
>
>The USB drive is not self-powered. It doesn't make a difference
>whether it's done directly after cold reset or:
>  usb -s
>  boot bnet
>  usb -s
>
>Cheers,
>Ahmad

I have reproduced that. My latest findings are that, when I debugged
this, usb core on my board I was debugging was behaving uncommon. It was
not setting the USB_PORT_STAT_C_CONNECTION in the first place. But the
further patches I send did solve this.

So this whole issue was due to an uncorrect configured over-current
polarity setup. With my other patches applied I see this bit
USB_PORT_STAT_C_CONNECTION set even without the power-cycle.

My suggestion is to _revert_ this patch, as it is solving a
bogus problem not related to the whole usb-core state machine.

Thanks for testing!
Michael

>>
>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>> ---
>>  drivers/usb/core/hub.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
>> index 01653d8c20..d1112248ee 100644
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -336,8 +336,7 @@ static void usb_scan_port(struct usb_device_scan *usb_scan)
>>  	dev_dbg(&dev->dev, "port%d: Status 0x%04x Change 0x%04x\n",
>>  			port + 1, portstatus, portchange);
>>
>> -	if (!(portchange & USB_PORT_STAT_C_CONNECTION) ||
>> -	    !(portstatus & USB_PORT_STAT_CONNECTION)) {
>> +	if (!(portstatus & USB_PORT_STAT_CONNECTION)) {
>>  		if (get_time_ns() >= hub->connect_timeout) {
>>  			dev_dbg(&dev->dev, "port%d: timeout\n", port + 1);
>>  			/* Remove this device from scanning list */
>>

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