1 files changed, 34 insertions, 7 deletions

diff --git a/chip/stm32/usb.c b/chip/stm32/usb.c
index dfec42b5f8..4aec16f8d3 100644
--- a/chip/stm32/usb.c
+++ b/chip/stm32/usb.c
@@ -384,11 +384,17 @@ static void usb_suspend(void)
 {
 	CPRINTF("SUS\n");
 
+	/*
+	 * usb_suspend can be called from hook task, make sure no interrupt is
+	 * modifying CNTR at the same time.
+	 */
+	interrupt_disable();
 	/* Set FSUSP bit to activate suspend mode */
 	STM32_USB_CNTR |= STM32_USB_CNTR_FSUSP;
 
 	/* Set USB low power mode */
 	STM32_USB_CNTR |= STM32_USB_CNTR_LP_MODE;
+	interrupt_enable();
 
 	clock_enable_module(MODULE_USB, 0);
 
@@ -396,15 +402,20 @@ static void usb_suspend(void)
 	enable_sleep(SLEEP_MASK_USB_DEVICE);
 }
 
-static void usb_resume(void)
+static void usb_resume_deferred(void)
 {
-	CPRINTF("RSM\n");
+	uint32_t state = (STM32_USB_FNR & STM32_USB_FNR_RXDP_RXDM_MASK)
+		>> STM32_USB_FNR_RXDP_RXDM_SHIFT;
 
-	/*
-	 * TODO(crosbug.com/p/63273): Reference manual suggests going back to
-	 * sleep if state is 10 or 11, but this seems to cause other problems
-	 * (see bug). Ignore them for now.
-	 */
+	CPRINTF("RSMd %d %04x\n", state, STM32_USB_CNTR);
+	if (state == 2 || state == 3)
+		usb_suspend();
+}
+DECLARE_DEFERRED(usb_resume_deferred);
+
+static void usb_resume(void)
+{
+	uint32_t state;
 
 	clock_enable_module(MODULE_USB, 1);
 
@@ -413,6 +424,22 @@ static void usb_resume(void)
 
 	/* USB is in use again */
 	disable_sleep(SLEEP_MASK_USB_DEVICE);
+
+	state = (STM32_USB_FNR & STM32_USB_FNR_RXDP_RXDM_MASK)
+		>> STM32_USB_FNR_RXDP_RXDM_SHIFT;
+
+	CPRINTF("RSM %d %04x\n", state, STM32_USB_CNTR);
+
+	/*
+	 * Reference manual tells we should go back to sleep if state is 10 or
+	 * 11. However, setting FSUSP and LP_MODE in this interrupt routine
+	 * seems to lock the USB controller (see b/35775088 and b/71688150).
+	 * Instead, we do it in a deferred routine. The host must assert the
+	 * reset condition for 20ms, so reading D+/D- after ~3ms should be safe
+	 * (there is no chance we end up sampling during a bus transaction).
+	 */
+	if (state == 2 || state == 3)
+		hook_call_deferred(&usb_resume_deferred_data, 3 * MSEC);
 }
 
 #ifdef CONFIG_USB_REMOTE_WAKEUP