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

[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.

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.

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 */
 
 
-- 
2.42.0.869.gea05f2083d-goog