ethernet: use atomic_* to access volatile variables

drivers/bdring.c

@@ -18,6 +18,7 @@
 
 #include LWIP_HOOK_FILENAME
 
+#include <stdatomic.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -206,7 +207,7 @@ size_t net_reapTxFinished(net_bufdesc_ring_t *ring)
 
 	n = 0;
 	i = ring->tail;
-	head = *(volatile unsigned *)&ring->head;
+	head = atomic_load(&ring->head);
 	while (i != head) {
 		if (!ring->ops->nextTxDone(ring, i))
 			break;
@@ -221,7 +222,7 @@ size_t net_reapTxFinished(net_bufdesc_ring_t *ring)
 	}
 
 	if (n)
-		*(volatile unsigned *)&ring->tail = i;
+		atomic_store(&ring->tail, i);
 
 	mutexUnlock(ring->lock);
 	return n;
@@ -275,7 +276,7 @@ size_t net_transmitPacket(net_bufdesc_ring_t *ring, struct pbuf *p)
 
 	mutexLock(ring->lock);
 	// NOTE: 2^n ring size verified in net_initRings
-	n = *(volatile unsigned *)&ring->tail;	// access tail once - it may be advanced by tx_done thread
+	n = atomic_load(&ring->tail);	// access tail once - it may be advanced by tx_done thread
 	i = ring->head;
 	n = (n - i - 1) & ring->last;
 	if (n > MAX_TX_FRAGMENTS)
@@ -300,8 +301,7 @@ size_t net_transmitPacket(net_bufdesc_ring_t *ring, struct pbuf *p)
 		last = 0;
 	}
 
-	asm volatile ("" ::: "memory");
-	*(volatile unsigned *)&ring->head = ni;	// sync with read in net_reapTxFinished() run in tx_done thread
+	atomic_store(&ring->head, ni);
 	mutexUnlock(ring->lock);
 	return frags;
 }

drivers/bdring.h

@@ -12,6 +12,7 @@
 #define PHOENIX_NET_BDRING_H_
 
 #include <sys/types.h>
+#include <stdatomic.h>
 #include "lwip/pbuf.h"
 
 
@@ -45,7 +46,8 @@ struct net_bufdesc_ring_
 {
 	volatile void *ring;
 	struct pbuf **bufp;
-	unsigned head, tail, last;
+	volatile unsigned head, tail;
+	unsigned last;
 	addr_t phys;
 	const net_bufdesc_ops_t *ops;
 	handle_t lock;
@@ -61,15 +63,10 @@ size_t net_transmitPacket(net_bufdesc_ring_t *ring, struct pbuf *p);
 
 static inline int net_rxFullyFilled(net_bufdesc_ring_t *ring)
 {
-	return ((ring->head - ring->tail) & ring->last) == 1;
-}
-
+	unsigned tail = atomic_load(&ring->tail);
+	unsigned head = atomic_load(&ring->head);
 
-static inline int net_txEmpty(net_bufdesc_ring_t *ring)
-{
-	// called from netport thread, races against irq/tx_done
-	return ring->head == *(volatile unsigned *)&ring->tail;
+	return ((head - tail) & ring->last) == 1;
 }
 
-
 #endif /* PHOENIX_NET_BDRING_H_ */

drivers/imx6-enet.c

@@ -22,6 +22,7 @@
 #include <sys/platform.h>
 #include <sys/threads.h>
 #include <phoenix/arch/imx6ull.h>
+#include <stdatomic.h>
 #include <endian.h>
 #include <errno.h>
 #include <stdarg.h>
@@ -316,11 +317,7 @@ static void enet_fillRxDesc(const net_bufdesc_ring_t *ring, size_t i, addr_t pa,
 #if USE_ENET_EXT_DESCRIPTORS
 	desc->yflags = ENET_RXDY_INT;
 #endif
-	asm ("" ::: "memory");
-
-	desc->flags = ENET_DESC_OWN | wrap;
-
-	asm ("" ::: "memory");
+	atomic_store(&desc->flags, ENET_DESC_OWN | wrap);
 }
 
 
@@ -355,11 +352,7 @@ static void enet_fillTxDesc(const net_bufdesc_ring_t *ring, size_t i, addr_t pa,
 	desc->yflags = yflags;
 #endif
 
-	asm ("" ::: "memory");
-
-	desc->flags = flags;
-
-	asm ("" ::: "memory");
+	atomic_store(&desc->flags, flags);
 }
 
 
@@ -404,7 +397,7 @@ static int enet_irq_handler(unsigned irq, void *arg)
 	state->mmio->EIMR &= ~(ENET_IRQ_RXF | ENET_IRQ_TXF);
 
 	if (events & ENET_IRQ_EBERR)
-		__sync_fetch_and_or(&state->drv_exit, EV_BUS_ERROR);	// FIXME: atomic_set()
+		atomic_fetch_or(&state->drv_exit, EV_BUS_ERROR);
 
 	return 0;
 }