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Date:   Thu, 26 Oct 2023 14:34:22 -0400
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Hardik Gajjar <hgajjar@de.adit-jv.com>
Cc:     gregkh@linuxfoundation.org, mathias.nyman@intel.com,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        erosca@de.adit-jv.com
Subject: Re: [PATCH v6] usb: Reduce the 'SET_ADDRESS' request timeout with a
 new quirk
Message-ID: <55a00749-7b9d-4fc8-a470-6eabdb93216f@rowland.harvard.edu>
References: <20231025164019.GA121292@vmlxhi-118.adit-jv.com>
 <20231026101551.36551-1-hgajjar@de.adit-jv.com>
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On Thu, Oct 26, 2023 at 12:15:51PM +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@de.adit-jv.com>
> ---

For the usbcore parts: A couple of very minor things can be improved.  
Once those improvements have been made, you can add:

Reviewed-by: Alan Stern <stern@rowland.harvard.edu>

> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 0a1731a0f0ef..4aa3723d2eaf 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6817,6 +6817,9 @@
>  					pause after every control message);
>  				o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
>  					delay after resetting its port);
> +				p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT (Reduce
> +					timeout of the SET_ADDRESS request from
> +					5000 ms to 500 ms)

To avoid going over the 80-column limit, move "(Reduce" to the next 
line and reflow the text in parentheses.

> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 3c54b218301c..98db92af2cce 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -54,6 +54,19 @@
>  #define USB_TP_TRANSMISSION_DELAY_MAX	65535	/* ns */
>  #define USB_PING_RESPONSE_TIME		400	/* ns */
>  
> +/*
> + * USB 3.2 spec, section 9.2.6.1
> + * USB sets an upper limit of 5000 ms for any command/request
> + * to be processed.
> + */
> +#define USB_DEFAULT_REQUEST_TIMEOUT_MS	5000 /* ms */

You don't need to define this macro at all.  Just use 
USB_CTRL_SET_TIMEOUT (which is already defined to be 5000) as the 
existing code already does.

> +/*
> + * The SET_ADDRESS request timeout will be 500 ms when
> + * USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT enable.
> + */
> +#define USB_SHORT_SET_ADDRESS_REQ_TIMEOUT_MS	500  /* ms */

As remarked earlier, we don't need to have the "_MS" suffix on either 
the macro name or the "timeout_ms" variable name.  Removing the suffix 
will be more consistent with the USB_TP_TRANSMISSION_DELAY_MAX and 
USB_PING_RESPONSE_TIME names you see above.

> +
> +/*
> + * The SET_ADDRESS request timeout will be 500 ms when
> + * USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT enable.

Change the second line to:

 *  the USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT quirk flag is set.

> + */
> +#define USB_SHORT_SET_ADDRESS_REQ_TIMEOUT_MS	500  /* ms */

Overall, I agree with Sergey that this would be cleaner if you split it 
up into two patches.  The first should change the comment for the 
set_address() callback function and the implementation in xhci-hcd.  The 
second should add the quirk flag and make the corresponding changes to 
the USB core.

Alan Stern