linux-kernel - Re: [PATCH v7 2/2] usb: new quirk to reduce the SET

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Date:   Fri, 3 Nov 2023 16:15:48 +0100
From:   Hardik Gajjar <hgajjar@...adit-jv.com>
To:     Alan Stern <stern@...land.harvard.edu>
CC:     Hardik Gajjar <hgajjar@...adit-jv.com>,
        <gregkh@...uxfoundation.org>, <mathias.nyman@...el.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <erosca@...adit-jv.com>, <s.shtylyov@....ru>
Subject: Re: [PATCH v7 2/2] usb: new quirk to reduce the SET_ADDRESS request
 timeout

On Fri, Oct 27, 2023 at 11:49:13AM -0400, Alan Stern wrote:
> On Fri, Oct 27, 2023 at 05:20:29PM +0200, Hardik Gajjar wrote:
> > This patch introduces a new USB quirk,
> > USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT, which modifies the timeout value
> > for the SET_ADDRESS request. The standard timeout for USB request/command
> > is 5000 ms, as recommended in the USB 3.2 specification (section 9.2.6.1).
> > 
> > However, certain scenarios, such as connecting devices through an APTIV
> > hub, can lead to timeout errors when the device enumerates as full speed
> > initially and later switches to high speed during chirp negotiation.
> > 
> > In such cases, USB analyzer logs reveal that the bus suspends for
> > 5 seconds due to incorrect chirp parsing and resumes only after two
> > consecutive timeout errors trigger a hub driver reset.
> > 
> > Packet(54) Dir(?) Full Speed J(997.100 us) Idle(  2.850 us)
> > _______| Time Stamp(28 . 105 910 682)
> > _______|_____________________________________________________________Ch0
> > Packet(55) Dir(?) Full Speed J(997.118 us) Idle(  2.850 us)
> > _______| Time Stamp(28 . 106 910 632)
> > _______|_____________________________________________________________Ch0
> > Packet(56) Dir(?) Full Speed J(399.650 us) Idle(222.582 us)
> > _______| Time Stamp(28 . 107 910 600)
> > _______|_____________________________________________________________Ch0
> > Packet(57) Dir Chirp J( 23.955 ms) Idle(115.169 ms)
> > _______| Time Stamp(28 . 108 532 832)
> > _______|_____________________________________________________________Ch0
> > Packet(58) Dir(?) Full Speed J (Suspend)( 5.347 sec) Idle(  5.366 us)
> > _______| Time Stamp(28 . 247 657 600)
> > _______|_____________________________________________________________Ch0
> > 
> > This 5-second delay in device enumeration is undesirable, particularly
> > in automotive applications where quick enumeration is crucial
> > (ideally within 3 seconds).
> > 
> > The newly introduced quirks provide the flexibility to align with a
> > 3-second time limit, as required in specific contexts like automotive
> > applications.
> > 
> > By reducing the SET_ADDRESS request timeout to 500 ms, the
> > system can respond more swiftly to errors, initiate rapid recovery, and
> > ensure efficient device enumeration. This change is vital for scenarios
> > where rapid smartphone enumeration and screen projection are essential.
> > 
> > To use the quirk, please write "vendor_id:product_id:p" to
> > /sys/bus/usb/drivers/hub/module/parameter/quirks
> > 
> > For example,
> > echo "0x2c48:0x0132:p" > /sys/bus/usb/drivers/hub/module/parameters/quirks"
> > 
> > Signed-off-by: Hardik Gajjar <hgajjar@...adit-jv.com>
> > ---
> 
> Reviewed-by: Alan Stern <stern@...land.harvard.edu>

@Greg KH, Friendly reminder.

Thanks,
Hardik