[nrf fromtree] nrf_usbd_common: Do not trigger DMA in low power mode

DMA transfers do not execute when the USBD peripheral is in Low Power
mode. Make sure that there is no DMA active transfer when entering Low
Power mode and that new DMA transfers are not started when in Low Power
mode because the transfer won't ever finish.

Signed-off-by: Tomasz Moń <[email protected]>
(cherry picked from commit cb1e7d6)

Author: tmon-nordic

drivers/usb/common/nrf_usbd_common/nrf_usbd_common.c

@@ -834,9 +834,10 @@ static void usbd_dmareq_process(void)
 {
 	if ((m_ep_dma_waiting & m_ep_ready) &&
 	    (k_sem_take(&dma_available, K_NO_WAIT) == 0)) {
+		const bool low_power = nrf_usbd_common_suspend_check();
 		uint32_t req;
 
-		while (0 != (req = m_ep_dma_waiting & m_ep_ready)) {
+		while (!low_power && 0 != (req = m_ep_dma_waiting & m_ep_ready)) {
 			uint8_t pos;
 
 			if (NRFX_USBD_CONFIG_DMASCHEDULER_ISO_BOOST &&
@@ -1310,7 +1311,11 @@ bool nrf_usbd_common_is_started(void)
 bool nrf_usbd_common_suspend(void)
 {
 	bool suspended = false;
-	unsigned int irq_lock_key = irq_lock();
+	unsigned int irq_lock_key;
+
+	/* DMA doesn't work in Low Power mode, ensure there is no active DMA */
+	k_sem_take(&dma_available, K_FOREVER);
+	irq_lock_key = irq_lock();
 
 	if (m_bus_suspend) {
 		if (!(NRF_USBD->EVENTCAUSE & USBD_EVENTCAUSE_RESUME_Msk)) {
@@ -1327,6 +1332,7 @@ bool nrf_usbd_common_suspend(void)
 	}
 
 	irq_unlock(irq_lock_key);
+	k_sem_give(&dma_available);
 
 	return suspended;
 }