Re: [PATCH v4 05/12] usb: Avoid unbinding devices in use by bootflows

Am 12. November 2023 21:02:42 MEZ schrieb Simon Glass sjg@chromium.org:

When a USB device is unbound, it causes any bootflows attached to it to be removed, via a call to bootdev_clear_bootflows() from bootdev_pre_unbind(). This obviously makes it impossible to boot the bootflow.

However, when booting a bootflow that relies on USB, usb_stop() is called, which unbinds the device. For EFI, this happens in efi_exit_boot_services() which means that the bootflow disappears before it is finished with.

After ExitBootServices() no driver of U-Boot can be used as the operating system is in charge.

Any bootflow inside U-Boot is terminated by definition when reaching ExitBootServices.

There is no need to unbind all the USB devices just to quiesce them. Add a new usb_pause() call which removes them but leaves them bound.

As U-Boot must not access any device after ExitBootServices() it is unclear to me what you want to achieve.

Best regards

Heinrich

This resolves a hang on x86 when booting a distro from USB. This was found using a device with 4 bootflows, the last of which was USB.

Signed-off-by: Simon Glass sjg@chromium.org

Changes in v4:

• Don't rename the legacy-USB functions
• Add a bit more detail to the comment

Changes in v2:

• Add new patch to avoid unbinding devices in use by bootflows

boot/bootm.c | 2 +- common/usb.c | 5 +++++ drivers/usb/host/usb-uclass.c | 14 ++++++++++++-- include/usb.h | 21 ++++++++++++++++++++- 4 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/boot/bootm.c b/boot/bootm.c index cb61485c226c..d9c3fa8dad99 100644 --- a/boot/bootm.c +++ b/boot/bootm.c @@ -502,7 +502,7 @@ ulong bootm_disable_interrupts(void) * updated every 1 ms within the HCCA structure in SDRAM! For more * details see the OpenHCI specification. */

• usb_stop();

• usb_pause();

#endif return iflag; } diff --git a/common/usb.c b/common/usb.c index 836506dcd9e9..a486d1c87d4d 100644 --- a/common/usb.c +++ b/common/usb.c @@ -144,6 +144,11 @@ int usb_stop(void) return 0; }

+int usb_pause(void) +{

• return usb_stop();

+}

/******************************************************************************

• Detect if a USB device has been plugged or unplugged.

*/ diff --git a/drivers/usb/host/usb-uclass.c b/drivers/usb/host/usb-uclass.c index a1cd0ad2d669..c26c65d7986b 100644 --- a/drivers/usb/host/usb-uclass.c +++ b/drivers/usb/host/usb-uclass.c @@ -173,7 +173,7 @@ int usb_get_max_xfer_size(struct usb_device *udev, size_t *size) return ops->get_max_xfer_size(bus, size); }

-int usb_stop(void) +static int usb_finish(bool unbind_all) { struct udevice *bus; struct udevice *rh; @@ -195,7 +195,7 @@ int usb_stop(void)

/* Locate root hub device */
device_find_first_child(bus, &rh);

• if (rh) {
  

• if (rh && unbind_all) {
  /*
   * All USB devices are children of root hub.
   * Unbinding root hub will unbind all of its children.
  

@@ -222,6 +222,16 @@ int usb_stop(void) return err; }

+int usb_stop(void) +{

• return usb_finish(true);

+}

+int usb_pause(void) +{

• return usb_finish(false);

+}

static void usb_scan_bus(struct udevice *bus, bool recurse) { struct usb_bus_priv *priv; diff --git a/include/usb.h b/include/usb.h index 09e3f0cb309c..b964e2e1f6b2 100644 --- a/include/usb.h +++ b/include/usb.h @@ -265,7 +265,26 @@ int usb_kbd_deregister(int force); */ int usb_init(void);

-int usb_stop(void); /* stop the USB Controller */ +/**

• • usb_stop() - stop the USB Controller and unbind all USB controllers/devices
• • This unbinds all devices on the USB buses.
• • Return: 0 if OK, -ve on error
• */

+int usb_stop(void);

+/**

• • usb_pause() - stop the USB Controller DMA, etc.
• • Note that this does not unbind bus devices, so using usb_init() after this
• • call is not permitted. This function is only useful just before booting, to
• • ensure that devices are dormant.
• • Return: 0 if OK, -ve on error
• */

+int usb_pause(void);

int usb_detect_change(void); /* detect if a USB device has been (un)plugged */