Date:   Sun, 5 Nov 2017 19:41:14 +0100
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     Alan Stern <stern@...land.harvard.edu>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <gregkh@...uxfoundation.org>, <linux@...ck-us.net>
Subject: Re: [PATCH][RFC] usb: hub: Cycle HUB power when initialization fails

On 03-11-17 18:27, Alan Stern wrote:
> On Fri, 3 Nov 2017, Mike Looijmans wrote:
> 
>> Sometimes the USB device gets confused about the state of the initialization and
>> the connection fails. In particular, the device thinks that it's already set up
>> and running while the host thinks the device still needs to be configured. To
> 
> How do you know that this is really the issue?  How can the device
> think it's already set if it doesn't have an assigned address?

It seems to me that the device just doesn't react at all on the host 
requests to assign an address. I've seen this happen with various custom 
mass-storage like appliances, but also DVB tuners and such. The device 
won't return to a working state until you unplug it and put it back, or, 
and that's what the patch does, just power-cycle the USB port, which has 
the same effect.

>> work around this issue, power-cycle the hub's output to issue a sort of "reset"
>> to the device. This makes the device restart its state machine and then the
>> initialization succeeds.
>>
>> This fixes problems where the kernel reports a list of errors like this:
>>
>> usb 1-1.3: device not accepting address 19, error -71
>>
>> The end result is a non-functioning device. After this patch, the sequence
>> becomes like this:
>>
>> usb 1-1.3: new high-speed USB device number 18 using ci_hdrc
>> usb 1-1.3: device not accepting address 18, error -71
>> usb 1-1.3: new high-speed USB device number 19 using ci_hdrc
>> usb 1-1.3: device not accepting address 19, error -71
>> usb 1-1-port3: attempt power cycle
>> usb 1-1.3: new high-speed USB device number 21 using ci_hdrc
>> usb-storage 1-1.3:1.2: USB Mass Storage device detected
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>> ---
>> This is a fix I did for a customer which might be appropriate for upstream. What do you think?
>>
>>   drivers/usb/core/hub.c | 13 ++++++++++---
>>   1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
>> index e9ce6bb..a30c1e7 100644
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -2611,7 +2611,7 @@ static unsigned hub_is_wusb(struct usb_hub *hub)
>>   #define PORT_RESET_TRIES	5
>>   #define SET_ADDRESS_TRIES	2
>>   #define GET_DESCRIPTOR_TRIES	2
>> -#define SET_CONFIG_TRIES	(2 * (use_both_schemes + 1))
>> +#define SET_CONFIG_TRIES	(4 * (use_both_schemes + 1))
> 
> We already have too many retry loops.  I am not keen on the idea of
> adding even more.  How about leaving this value the same and adding the
> power cycle?

I'm fine with that as well.

> The ideal, however, would be to find out what is wrong with the device
> and see what needs to be done to fix it properly.  This change won't
> work on many computers (desktops and laptops) because they don't have
> real USB port-power switching.  A lot of hubs don't have it either.

I'm pretty sure it's the device's fault, but they're out there and 
probably not upgradable anyway if you could get the manufacturer to pick 
up the phone.

On desktop/laptop machines the problem isn't as pressing since there's a 
often a user there who can unplug the thing. It's really nasty on 
embedded systems, and they tend to have the USB power wired through a 
supply limiter/switch.
I'm thinking worst that could happen on desktops is that the patch won't 
have any effect at all.

So what do you think, is this worth a v2 patch for general consumption 
or should I keep this a "private" patch for systems that have 
demonstrated to benefit from it?


>>   #define USE_NEW_SCHEME(i)	((i) / 2 == (int)old_scheme_first)
>>   
>>   #define HUB_ROOT_RESET_TIME	60	/* times are in msec */
>> @@ -4805,7 +4805,6 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
>>   
>>   	status = 0;
>>   	for (i = 0; i < SET_CONFIG_TRIES; i++) {
>> -
> 
> Gratuitous whitespace change.
> 
>>   		/* reallocate for each attempt, since references
>>   		 * to the previous one can escape in various ways
>>   		 */
>> @@ -4935,6 +4934,15 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
>>   		usb_put_dev(udev);
>>   		if ((status == -ENOTCONN) || (status == -ENOTSUPP))
>>   			break;
>> +
>> +		/* When halfway through our retry count, power-cycle the port */
>> +		if (i == (SET_CONFIG_TRIES / 2) - 1) {
>> +			dev_info(&port_dev->dev, "attempt power cycle\n");
>> +			usb_hub_set_port_power(hdev, hub, port1, false);
>> +			msleep(800);
>> +			usb_hub_set_port_power(hdev, hub, port1, true);
>> +			msleep(hub_power_on_good_delay(hub));
>> +		}
>>   	}
>>   	if (hub->hdev->parent ||
>>   			!hcd->driver->port_handed_over ||
>> @@ -5476,7 +5484,6 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
>>   	udev->bos = NULL;
>>   
>>   	for (i = 0; i < SET_CONFIG_TRIES; ++i) {
>> -
> 
> Another gratuitous change.
> 
>>   		/* ep0 maxpacket size may change; let the HCD know about it.
>>   		 * Other endpoints will be handled by re-enumeration. */
>>   		usb_ep0_reinit(udev);
> 
> Alan Stern
> 


-- 
Mike Looijmans


Kind regards,

Mike Looijmans
System Expert

TOPIC Products
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E-mail: mike.looijmans@...icproducts.com
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