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Date:   Wed, 25 Oct 2023 19:00:06 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Hardik Gajjar <hgajjar@...adit-jv.com>,
        <gregkh@...uxfoundation.org>, <stern@...land.harvard.edu>,
        <mathias.nyman@...el.com>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <erosca@...adit-jv.com>
Subject: Re: [PATCH v5] usb: Reduce 'set_address' command timeout with a new
 quirk

Hello!

On 10/25/23 5:13 PM, Hardik Gajjar wrote:

   Sorry to be PITA but... (-:

> This patch introduces a new USB quirk, USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT,
> which modifies the timeout value for the 'set_address' command. The

   This is called a request, not a command by the spec. And the USB spec
names the requests in all uppercase, e.g. SET_ADDRESS...

> standard timeout for this command is 5000 ms, as recommended in the USB
> 3.2 specification (section 9.2.6.1).

   This section in the USB specs 1.1/2.0/3.0 talks about _all_ requests.
I don't have USB 3.2 but It believe it has the same wording.

[...]

> Signed-off-by: Hardik Gajjar <hgajjar@...adit-jv.com>
[...]

> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 0a1731a0f0ef..3c03f23bd5d5 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_DEVICE_ADDR_TIMEOUT (Timeout
> +					of set_address command reducing from

   Please, "The SET_ADDRESS request" instead...

> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 3c54b218301c..3594eeb892ac 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -54,6 +54,18 @@
>  #define USB_TP_TRANSMISSION_DELAY_MAX	65535	/* ns */
>  #define USB_PING_RESPONSE_TIME		400	/* ns */
>  
> +/*
> + * address device command timeout 5000 ms is recommended in

   What address device command? Are you sure you're not mixing
the USB and xHCI terminologies?

> + * USB 3.2 spec, section 9.2.6.1
> + */
> +#define USB_DEFAULT_ADDR_DEVICE_TIMEOUT_MS	5000 /* ms */
> +
> +/*
> + * address device command timeout will be 500 ms when

   Same here. This is a generic USB file, not the xHCI driver...

> + * USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT enable.
> + */
> +#define USB_SHORT_ADDR_DEVICE_TIMEOUT_MS	500  /* ms */
> +
>  /* Protect struct usb_device->state and ->children members
>   * Note: Both are also protected by ->dev.sem, except that ->state can
>   * change to USB_STATE_NOTATTACHED even when the semaphore isn't held. */
[...]
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index e1b1b64a0723..0c610a853aef 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -3998,11 +3998,17 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
>  }
>  
>  /*

   You seem to be converting the existing comment to a kernel-doc one
but you miss changing from /* /** at the start and adding colons after
the param names below...

> - * Issue an Address Device command and optionally send a corresponding
> - * SetAddress request to the device.
> + * xhci_setup_device - issues an Address Device command to assign a unique
> + *			USB bus address.
> + * @hcd USB host controller data structure.
> + * @udev USB dev structure representing the connected device.
> + * @setup Enum specifying setup mode: address only or with context.
> + * @timeout_ms Max wait time (ms) for the command operation to complete.
> + *
> + * Return: 0 if successful; otherwise, negative error code.
>   */
>  static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
> -			     enum xhci_setup_dev setup)
> +			     enum xhci_setup_dev setup, unsigned int timeout_ms)
[...]

MBR, Sergey

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