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Date:   Mon, 9 Oct 2023 19:43:09 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Hardik Gajjar <hgajjar@de.adit-jv.com>
Cc:     mathias.nyman@intel.com, stern@rowland.harvard.edu,
        yangyingliang@huawei.com, jinpu.wang@ionos.com,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        erosca@de.adit-jv.com
Subject: Re: [PATCH v2] usb: core: hub: Add quirks for reducing device
 address timeout
Message-ID: <2023100921-likeness-possible-032c@gregkh>
References: <--in-reply-to=20231006153808.9758-1-hgajjar@de.adit-jv.com>
 <20231009161402.104224-1-hgajjar@de.adit-jv.com>
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In-Reply-To: <20231009161402.104224-1-hgajjar@de.adit-jv.com>
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On Mon, Oct 09, 2023 at 06:14:02PM +0200, Hardik Gajjar wrote:
> Currently, the timeout for the set address command is fixed at
> 5 seconds in the xhci driver. This means the host waits up to 5
> seconds to receive a response for the set_address command from
> the device.
> 
> In the automotive context, most smartphone enumerations, including
> screen projection, should ideally complete within 3 seconds.
> Achieving this is impossible in scenarios where the set_address is
> not successful and waits for a timeout.
> 
> The shortened address device timeout quirks provide the flexibility
> to align with a 3-second time limit in the event of errors.
> By swiftly triggering a failure response and swiftly initiating
> retry procedures, these quirks ensure efficient and rapid recovery,
> particularly in automotive contexts where rapid smartphone enumeration
> and screen projection are vital.

So you have known-broken devices where you want a shorter error timeout?
But you don't list those devices in this patch adding the quirk
settings, shouldn't that be required, otherwise this looks like an
unused quirk.

> The quirk will set the timeout to 500 ms from 5 seconds.
> 
> 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/parameter/quirks"
> 
> Signed-off-by: Hardik Gajjar <hgajjar@de.adit-jv.com>
> ---
> changes since version 1:
> 	- implement quirk instead of new API in xhci driver
> ---
>  drivers/usb/core/hub.c       | 15 +++++++++++++--
>  drivers/usb/core/quirks.c    |  3 +++
>  drivers/usb/host/xhci-mem.c  |  1 +
>  drivers/usb/host/xhci-ring.c |  3 ++-
>  drivers/usb/host/xhci.c      |  9 +++++----
>  drivers/usb/host/xhci.h      |  1 +
>  include/linux/usb/hcd.h      |  3 ++-
>  include/linux/usb/quirks.h   |  3 +++
>  8 files changed, 30 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 3c54b218301c..975449b03426 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -54,6 +54,9 @@
>  #define USB_TP_TRANSMISSION_DELAY_MAX	65535	/* ns */
>  #define USB_PING_RESPONSE_TIME		400	/* ns */
>  
> +#define USB_DEFAULT_ADDR_DEVICE_TIMEOUT		(HZ * 5) /* 5000ms */
> +#define USB_SHORT_ADDR_DEVICE_TIMEOUT		125  /* ~500ms */
> +
>  /* 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. */
> @@ -4626,8 +4629,16 @@ EXPORT_SYMBOL_GPL(usb_ep0_reinit);
>  static int hub_set_address(struct usb_device *udev, int devnum)
>  {
>  	int retval;
> +	int timeout = USB_DEFAULT_ADDR_DEVICE_TIMEOUT;
>  	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
>  
> +	struct usb_hub *hub = usb_hub_to_struct_hub(udev->parent);
> +
> +	if (hub->hdev->quirks & USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT)
> +		timeout = USB_SHORT_ADDR_DEVICE_TIMEOUT;
> +
> +	dev_dbg(&udev->dev, "address_device timeout %d\n", timeout);

Is this debugging code still needed?

>  	/*
>  	 * The host controller will choose the device address,
>  	 * instead of the core having chosen it earlier
> @@ -4639,11 +4650,11 @@ static int hub_set_address(struct usb_device *udev, int devnum)
>  	if (udev->state != USB_STATE_DEFAULT)
>  		return -EINVAL;
>  	if (hcd->driver->address_device)
> -		retval = hcd->driver->address_device(hcd, udev);
> +		retval = hcd->driver->address_device(hcd, udev, timeout);
>  	else
>  		retval = usb_control_msg(udev, usb_sndaddr0pipe(),
>  				USB_REQ_SET_ADDRESS, 0, devnum, 0,
> -				NULL, 0, USB_CTRL_SET_TIMEOUT);
> +				NULL, 0, jiffies_to_msecs(timeout));
>  	if (retval == 0) {
>  		update_devnum(udev, devnum);
>  		/* Device now using proper address. */
> diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
> index 15e9bd180a1d..01ed26bd41f0 100644
> --- a/drivers/usb/core/quirks.c
> +++ b/drivers/usb/core/quirks.c
> @@ -138,6 +138,9 @@ static int quirks_param_set(const char *value, const struct kernel_param *kp)
>  			case 'o':
>  				flags |= USB_QUIRK_HUB_SLOW_RESET;
>  				break;
> +			case 'p':
> +				flags |= USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT;
> +				break;
>  			/* Ignore unrecognized flag characters */
>  			}
>  		}
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 8714ab5bf04d..492433fdac77 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -1729,6 +1729,7 @@ struct xhci_command *xhci_alloc_command(struct xhci_hcd *xhci,
>  	}
>  
>  	command->status = 0;
> +	command->timeout = 0;
>  	INIT_LIST_HEAD(&command->cmd_list);
>  	return command;
>  }
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 1dde53f6eb31..0bd19a1efdec 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -4301,7 +4301,8 @@ static int queue_command(struct xhci_hcd *xhci, struct xhci_command *cmd,
>  	/* if there are no other commands queued we start the timeout timer */
>  	if (list_empty(&xhci->cmd_list)) {
>  		xhci->current_cmd = cmd;
> -		xhci_mod_cmd_timer(xhci, XHCI_CMD_DEFAULT_TIMEOUT);
> +		xhci_mod_cmd_timer(xhci, (cmd->timeout) ? cmd->timeout :
> +				XHCI_CMD_DEFAULT_TIMEOUT);
>  	}
>  
>  	list_add_tail(&cmd->cmd_list, &xhci->cmd_list);
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index e1b1b64a0723..1d088ceb2b74 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -4002,7 +4002,7 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
>   * SetAddress request to the device.
>   */
>  static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
> -			     enum xhci_setup_dev setup)
> +			     enum xhci_setup_dev setup, int timeout)

What is the units of timeout here?

>  {
>  	const char *act = setup == SETUP_CONTEXT_ONLY ? "context" : "address";
>  	unsigned long flags;
> @@ -4059,6 +4059,7 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
>  	}
>  
>  	command->in_ctx = virt_dev->in_ctx;
> +	command->timeout = timeout;
>  
>  	slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->in_ctx);
>  	ctrl_ctx = xhci_get_input_control_ctx(virt_dev->in_ctx);
> @@ -4185,14 +4186,14 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
>  	return ret;
>  }
>  
> -static int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
> +static int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev, int timeout)
>  {
> -	return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ADDRESS);
> +	return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ADDRESS, timeout);
>  }
>  
>  static int xhci_enable_device(struct usb_hcd *hcd, struct usb_device *udev)
>  {
> -	return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ONLY);
> +	return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ONLY, 0);

0 is no timeout at all?  Or max timeout?  Where is this documented?

And why is this only added to the xhci driver and not all other host
controllers?

>  }
>  
>  /*
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 7e282b4522c0..ebdca8dd01c2 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -818,6 +818,7 @@ struct xhci_command {
>  	struct completion		*completion;
>  	union xhci_trb			*command_trb;
>  	struct list_head		cmd_list;
> +	int				timeout;

What is the units here.

>  };
>  
>  /* drop context bitmasks */
> diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
> index 61d4f0b793dc..b0fda87ad3a2 100644
> --- a/include/linux/usb/hcd.h
> +++ b/include/linux/usb/hcd.h
> @@ -373,7 +373,8 @@ struct hc_driver {
>  		 */
>  	void	(*reset_bandwidth)(struct usb_hcd *, struct usb_device *);
>  		/* Returns the hardware-chosen device address */
> -	int	(*address_device)(struct usb_hcd *, struct usb_device *udev);
> +	int	(*address_device)(struct usb_hcd *, struct usb_device *udev,
> +				  int timeout);

Again, units please.

>  		/* prepares the hardware to send commands to the device */
>  	int	(*enable_device)(struct usb_hcd *, struct usb_device *udev);
>  		/* Notifies the HCD after a hub descriptor is fetched.
> diff --git a/include/linux/usb/quirks.h b/include/linux/usb/quirks.h
> index eeb7c2157c72..0cb464e3eaf4 100644
> --- a/include/linux/usb/quirks.h
> +++ b/include/linux/usb/quirks.h
> @@ -72,4 +72,7 @@
>  /* device has endpoints that should be ignored */
>  #define USB_QUIRK_ENDPOINT_IGNORE		BIT(15)
>  
> +/* short device address timeout */
> +#define USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT	BIT(16)

Don't you also need to have a Documentation/ update for the new
user/kernel api you are adding?

thanks,

greg k-h