[PATCH] net: macb: ensure the device is available before accessing GEMGXL control registers

[Zong Li]

If runtime power menagement is enabled, the gigabit ethernet PLL would
be disabled after macb_probe(). During this period of time, the system
would hang up if we try to access GEMGXL control registers.

We can't put runtime_pm_get/runtime_pm_put/ there due to the issue of
sleep inside atomic section (7fa2955ff70ce453 ("sh_eth: Fix sleeping
function called from invalid context"). Add the similar flag to ensure
the device is available before accessing GEMGXL device.

Signed-off-by: Zong Li <zong.li at sifive.com>
---
 drivers/net/ethernet/cadence/macb.h      | 2 ++
 drivers/net/ethernet/cadence/macb_main.c | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index d8d87213697c..acf5242ce715 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -1309,6 +1309,8 @@ struct macb {
 
 	u32	rx_intr_mask;
 
+	unsigned int is_opened;
+
 	struct macb_pm_data pm_data;
 	const struct macb_usrio_config *usrio;
 };
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 6bc7d41d519b..e079ed10ad91 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -2781,6 +2781,8 @@ static int macb_open(struct net_device *dev)
 	if (bp->ptp_info)
 		bp->ptp_info->ptp_init(dev);
 
+	bp->is_opened = 1;
+
 	return 0;
 
 reset_hw:
@@ -2818,6 +2820,8 @@ static int macb_close(struct net_device *dev)
 	if (bp->ptp_info)
 		bp->ptp_info->ptp_remove(dev);
 
+	bp->is_opened = 0;
+
 	pm_runtime_put(&bp->pdev->dev);
 
 	return 0;
@@ -2867,6 +2871,9 @@ static struct net_device_stats *gem_get_stats(struct macb *bp)
 	struct gem_stats *hwstat = &bp->hw_stats.gem;
 	struct net_device_stats *nstat = &bp->dev->stats;
 
+	if (!bp->is_opened)
+		return nstat;
+
 	gem_update_stats(bp);
 
 	nstat->rx_errors = (hwstat->rx_frame_check_sequence_errors +
-- 
2.31.1