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Message-ID: <YxIX+jqWFfwAWYot@rowland.harvard.edu>
Date: Fri, 2 Sep 2022 10:49:30 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Ray Chi <raychi@...gle.com>
Cc: gregkh@...uxfoundation.org, mathias.nyman@...ux.intel.com,
albertccwang@...gle.com, badhri@...gle.com, pumahsu@...gle.com,
linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v2] usb: core: stop USB enumeration if too many retries
On Fri, Sep 02, 2022 at 05:15:35PM +0800, Ray Chi wrote:
> If a broken accessory connected to a USB host, usbcore might
> keep doing enumeration retries and it will take a long time to
> cause system unstable.
>
> This patch provides a quirk to specific USB ports of the hub to
> stop USB enumeration if needed.
This seems very awkward. Why not have a quirk that prevents USB
enumeration completely, instead of after some number of retries? After
all, if the port is connected to a broken accessory, there's no reason
to try enumerating it even once.
For that matter, have you tried using the existing "disabled" port
attribute instead of adding a new quirk? Does it already solve your
problem?
>
> Signed-off-by: Ray Chi <raychi@...gle.com>
> ---
> Changes since v1:
> - remove usb_hub_set_port_power()
> - add a variable ignore_connect into struct port_dev
> - modify hub_port_stop_enumerate() and set ignore_connect in
> this function
> - avoid calling hub_port_connect_change() in port_event()
> ---
> drivers/usb/core/hub.c | 40 ++++++++++++++++++++++++++++++++++++++++
> drivers/usb/core/hub.h | 2 ++
> include/linux/usb.h | 3 +++
> 3 files changed, 45 insertions(+)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 2633acde7ac1..7f34ee8bb81e 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3081,6 +3081,30 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
> return status;
> }
>
> +/* Stop enumerate if the port met errors and quirk is set */
> +static bool hub_port_stop_enumerate(struct usb_hub *hub, int port1, int retries)
> +{
> + struct usb_port *port_dev = hub->ports[port1 - 1];
> +
> + if (port_dev->quirks & USB_PORT_QUIRK_STOP_ENUM) {
> + if (port_dev->ignore_connect)
> + return true;
> +
> + if (retries < (PORT_INIT_TRIES - 1) / 2)
> + return false;
> +
> + /*
> + * Some USB hosts can't take a long time to keep doing enumeration
> + * retry. After doing half of the retries, we would turn off the port
> + * power to stop enumeration if the quirk is set.
What made you decide that half of the retries was the right place to
stop? Why not do all the retries?
> + */
> + port_dev->ignore_connect = true;
> + } else
> + port_dev->ignore_connect = false;
> +
> + return port_dev->ignore_connect;
> +}
If the quirk prevented enumeration completely then this function
wouldn't be needed.
> +
> /* Check if a port is power on */
> int usb_port_is_power_on(struct usb_hub *hub, unsigned int portstatus)
> {
> @@ -4855,6 +4879,11 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
> buf->bMaxPacketSize0;
> kfree(buf);
>
> + if (r < 0 && (port_dev->quirks & USB_PORT_QUIRK_STOP_ENUM)) {
How come this line tests the quirk but doesn't call
hub_port_stop_enumerate()?
> + retval = r;
> + goto fail;
> + }
> +
> retval = hub_port_reset(hub, port1, udev, delay, false);
> if (retval < 0) /* error or disconnect */
> goto fail;
> @@ -5387,6 +5416,9 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
> if ((status == -ENOTCONN) || (status == -ENOTSUPP))
> break;
>
> + if (hub_port_stop_enumerate(hub, port1, i))
> + break;
> +
> /* When halfway through our retry count, power-cycle the port */
> if (i == (PORT_INIT_TRIES - 1) / 2) {
> dev_info(&port_dev->dev, "attempt power cycle\n");
> @@ -5550,6 +5582,9 @@ static void port_event(struct usb_hub *hub, int port1)
> if (usb_hub_port_status(hub, port1, &portstatus, &portchange) < 0)
> return;
>
> + if (hub_port_stop_enumerate(hub, port1, 0))
> + return;
This test is in the wrong place. It should go right next to the check
for pm_runtime_active(&port_dev->dev); even though the port isn't being
used we still want to turn off the port-change bits in the port status.
> +
> if (portchange & USB_PORT_STAT_C_CONNECTION) {
> usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
> connect_change = 1;
> @@ -5934,6 +5969,9 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
> ret = hub_port_init(parent_hub, udev, port1, i);
> if (ret >= 0 || ret == -ENOTCONN || ret == -ENODEV)
> break;
> +
> + if (hub_port_stop_enumerate(parent_hub, port1, i))
> + goto stop_enumerate;
Also this -- the purpose is to avoid calling hub_port_init() for ports
with the quirk, so this test belongs before the call to hub_port_init(),
not after.
> }
> mutex_unlock(hcd->address0_mutex);
>
> @@ -6022,6 +6060,8 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
> udev->bos = bos;
> return 0;
>
> +stop_enumerate:
> + mutex_unlock(hcd->address0_mutex);
> re_enumerate:
> usb_release_bos_descriptor(udev);
> udev->bos = bos;
> diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
> index b2925856b4cb..f0aa718f4c7f 100644
> --- a/drivers/usb/core/hub.h
> +++ b/drivers/usb/core/hub.h
> @@ -90,6 +90,7 @@ struct usb_hub {
> * @is_superspeed cache super-speed status
> * @usb3_lpm_u1_permit: whether USB3 U1 LPM is permitted.
> * @usb3_lpm_u2_permit: whether USB3 U2 LPM is permitted.
> + * @ignore_connect: ignore the connection or not
> */
> struct usb_port {
> struct usb_device *child;
> @@ -103,6 +104,7 @@ struct usb_port {
> u32 over_current_count;
> u8 portnum;
> u32 quirks;
> + bool ignore_connect;
This should be a bitfield like the following entries. It's okay to make
it a bool rather than unsigned int. But you may find that you don't
need this field at all.
> unsigned int is_superspeed:1;
> unsigned int usb3_lpm_u1_permit:1;
> unsigned int usb3_lpm_u2_permit:1;
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index f7a9914fc97f..fc0fef58c706 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -490,6 +490,9 @@ enum usb_port_connect_type {
> /* Decrease TRSTRCY to 10ms during device enumeration. */
> #define USB_PORT_QUIRK_FAST_ENUM BIT(1)
>
> +/* Stop the enumeration for the given port if there are too many failures*/
> +#define USB_PORT_QUIRK_STOP_ENUM BIT(2)
When you define a new port quirk, you have to document it in the
/sys/bus/usb/devices/.../<hub_interface>/port<X>/quirks section of
Documentation/ABI/testing/sysfs-bus-usb.
Alan Stern
> +
> /*
> * USB 2.0 Link Power Management (LPM) parameters.
> */
> --
> 2.37.2.789.g6183377224-goog
>
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