[PATCH RFC] qca_spi: Make interrupt remembering atomic

[Stefan Wahren]

The whole mechanism to remember occurred SPI interrupts is not atomic,
which could lead to unexpected behavior. So fix this by using atomic bit
operations instead.

Fixes: 291ab06ecf67 ("net: qualcomm: new Ethernet over SPI driver for QCA7000")
Signed-off-by: Stefan Wahren <wahrenst@xxxxxxx>
---
 drivers/net/ethernet/qualcomm/qca_debug.c |  6 ++----
 drivers/net/ethernet/qualcomm/qca_spi.c   | 16 ++++++++--------
 drivers/net/ethernet/qualcomm/qca_spi.h   |  3 +--
 3 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/qca_debug.c b/drivers/net/ethernet/qualcomm/qca_debug.c
index ff3b89e9028e..ad06da0fdaa0 100644
--- a/drivers/net/ethernet/qualcomm/qca_debug.c
+++ b/drivers/net/ethernet/qualcomm/qca_debug.c
@@ -98,10 +98,8 @@ qcaspi_info_show(struct seq_file *s, void *what)

 	seq_printf(s, "IRQ              : %d\n",
 		   qca->spi_dev->irq);
-	seq_printf(s, "INTR REQ         : %u\n",
-		   qca->intr_req);
-	seq_printf(s, "INTR SVC         : %u\n",
-		   qca->intr_svc);
+	seq_printf(s, "INTR             : %lx\n",
+		   qca->intr);

 	seq_printf(s, "SPI max speed    : %lu\n",
 		   (unsigned long)qca->spi_dev->max_speed_hz);
diff --git a/drivers/net/ethernet/qualcomm/qca_spi.c b/drivers/net/ethernet/qualcomm/qca_spi.c
index 5799ecc88a87..8f7ce6b51a1c 100644
--- a/drivers/net/ethernet/qualcomm/qca_spi.c
+++ b/drivers/net/ethernet/qualcomm/qca_spi.c
@@ -35,6 +35,8 @@

 #define MAX_DMA_BURST_LEN 5000

+#define SPI_INTR 0
+
 /*   Modules parameters     */
 #define QCASPI_CLK_SPEED_MIN 1000000
 #define QCASPI_CLK_SPEED_MAX 16000000
@@ -579,14 +581,14 @@ qcaspi_spi_thread(void *data)
 			continue;
 		}

-		if ((qca->intr_req == qca->intr_svc) &&
+		if (!test_bit(SPI_INTR, &qca->intr) &&
 		    !qca->txr.skb[qca->txr.head])
 			schedule();

 		set_current_state(TASK_RUNNING);

-		netdev_dbg(qca->net_dev, "have work to do. int: %d, tx_skb: %p\n",
-			   qca->intr_req - qca->intr_svc,
+		netdev_dbg(qca->net_dev, "have work to do. int: %lu, tx_skb: %p\n",
+			   qca->intr,
 			   qca->txr.skb[qca->txr.head]);

 		qcaspi_qca7k_sync(qca, QCASPI_EVENT_UPDATE);
@@ -600,8 +602,7 @@ qcaspi_spi_thread(void *data)
 			msleep(QCASPI_QCA7K_REBOOT_TIME_MS);
 		}

-		if (qca->intr_svc != qca->intr_req) {
-			qca->intr_svc = qca->intr_req;
+		if (test_and_clear_bit(SPI_INTR, &qca->intr)) {
 			start_spi_intr_handling(qca, &intr_cause);

 			if (intr_cause & SPI_INT_CPU_ON) {
@@ -663,7 +664,7 @@ qcaspi_intr_handler(int irq, void *data)
 {
 	struct qcaspi *qca = data;

-	qca->intr_req++;
+	set_bit(SPI_INTR, &qca->intr);
 	if (qca->spi_thread)
 		wake_up_process(qca->spi_thread);

@@ -679,8 +680,7 @@ qcaspi_netdev_open(struct net_device *dev)
 	if (!qca)
 		return -EINVAL;

-	qca->intr_req = 1;
-	qca->intr_svc = 0;
+	set_bit(SPI_INTR, &qca->intr);
 	qca->sync = QCASPI_SYNC_UNKNOWN;
 	qcafrm_fsm_init_spi(&qca->frm_handle);

diff --git a/drivers/net/ethernet/qualcomm/qca_spi.h b/drivers/net/ethernet/qualcomm/qca_spi.h
index d59cb2352cee..8f4808695e82 100644
--- a/drivers/net/ethernet/qualcomm/qca_spi.h
+++ b/drivers/net/ethernet/qualcomm/qca_spi.h
@@ -81,8 +81,7 @@ struct qcaspi {
 	struct qcafrm_handle frm_handle;
 	struct sk_buff *rx_skb;

-	unsigned int intr_req;
-	unsigned int intr_svc;
+	unsigned long intr;
 	u16 reset_count;

 #ifdef CONFIG_DEBUG_FS
--
2.34.1