if_atsam: Recover from receive freezes

Under unknown conditions the receive path ended up in a frozen state.
In this state, the DMA and driver descriptor head were equal and all
receive descriptors had the used bit set.  So, the DMA was unable to
store received frames.  However, the receive daemon was never woken up
to refill the receive buffers.  It seems that the RXUBR interrupt can be
used to recover from this state.

Update #4652.

1 files changed, 15 insertions, 5 deletions

diff --git a/rtemsbsd/sys/dev/atsam/if_atsam.c b/rtemsbsd/sys/dev/atsam/if_atsam.c
index fff21c65..21a28fcd 100644
--- a/rtemsbsd/sys/dev/atsam/if_atsam.c
+++ b/rtemsbsd/sys/dev/atsam/if_atsam.c
@@ -108,6 +108,8 @@
 #define MDIO_PHY MII_PHY_ANY
 #define IGNORE_RX_ERR false
 
+#define RX_INTERRUPTS (GMAC_ISR_RCOMP | GMAC_ISR_RXUBR | GMAC_ISR_ROVR)
+
 #define RX_DESC_LOG2 3
 #define RX_DESC_COUNT (1U << RX_DESC_LOG2)
 #define RX_DESC_WRAP(idx) \
@@ -187,6 +189,7 @@ typedef struct if_atsam_softc {
 	struct if_atsam_stats {
 		/* Software */
 		uint32_t rx_overrun_errors;
+		uint32_t rx_used_bit_reads;
 		uint32_t rx_interrupts;
 		uint32_t tx_tur_errors;
 		uint32_t tx_rlex_errors;
@@ -400,15 +403,19 @@ static void if_atsam_interrupt_handler(void *arg)
 	}
 
 	/* Check receive interrupts */
-	if (__predict_true((is & (GMAC_IER_ROVR | GMAC_IER_RCOMP)) != 0)) {
-		if (__predict_false((is & GMAC_IER_ROVR) != 0)) {
+	if (__predict_true((is & RX_INTERRUPTS) != 0)) {
+		if (__predict_false((is & GMAC_ISR_RXUBR) != 0)) {
+			++sc->stats.rx_used_bit_reads;
+		}
+
+		if (__predict_false((is & GMAC_ISR_ROVR) != 0)) {
 			++sc->stats.rx_overrun_errors;
 		}
 
 		++sc->stats.rx_interrupts;
 
-		/* Erase the interrupts for RX completion and errors */
-		pHw->GMAC_IDR = GMAC_IER_RCOMP | GMAC_IER_ROVR;
+		/* Disable RX interrupts */
+		pHw->GMAC_IDR = RX_INTERRUPTS;
 
 		(void)rtems_event_send(sc->rx_daemon_tid,
 		    ATSAMV7_ETH_RX_EVENT_INTERRUPT);
@@ -511,7 +518,7 @@ if_atsam_rx_daemon(rtems_task_argument arg)
 		sc->rx_idx_head = idx;
 
 		/* Enable RX interrupts */
-		pHw->GMAC_IER = GMAC_IER_RCOMP | GMAC_IER_ROVR;
+		pHw->GMAC_IER = RX_INTERRUPTS;
 
 		(void) rtems_event_receive(ATSAMV7_ETH_RX_EVENT_INTERRUPT,
 		    RTEMS_EVENT_ALL | RTEMS_WAIT, RTEMS_NO_TIMEOUT, &out);
@@ -1292,6 +1299,9 @@ if_atsam_add_sysctls(device_t dev)
 	SYSCTL_ADD_UINT(ctx, child, OID_AUTO, "rx_overrun_errors",
 	    CTLFLAG_RD, &sc->stats.rx_overrun_errors, 0,
 	    "RX overrun errors");
+	SYSCTL_ADD_UINT(ctx, child, OID_AUTO, "rx_used_bit_reads",
+	    CTLFLAG_RD, &sc->stats.rx_used_bit_reads, 0,
+	    "RX used bit reads");
 	SYSCTL_ADD_UINT(ctx, child, OID_AUTO, "rx_interrupts",
 	    CTLFLAG_RD, &sc->stats.rx_interrupts, 0,
 	    "Rx interrupts");