[PATCH net-next v4 3/6] net: ravb: Return cached statistics if the interface is down

[Claudiu <claudiu.beznea@tuxon.dev>]

From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

Return the cached statistics in case the interface is down. There should be
no drawback to this, as cached statistics are updated in ravb_close().

In order to avoid accessing the IP registers while the IP is runtime
suspended pm_runtime_active() check was introduced. The device runtime
PM usage counter has been incremented to avoid disabling the device clocks
while the check is in progress (if any).

The commit prepares the code for the addition of runtime PM support.

Suggested-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---

Changes in v4:
- none

Changes in v3:
- none

Changes in v2:
- collected tag

Changes since [2]:
- use pm_runtime_get_noresume() and pm_runtime_active()

Changes in v3 of [2]:
- this was patch 18/21 in v2
- use ndev->flags & IFF_UP instead of netif_running checks

Changes in v2 of [2]:
- none; this patch is new

[2] https://lore.kernel.org/all/20240105082339.1468817-1-claudiu.beznea.uj@bp.renesas.com/

 drivers/net/ethernet/renesas/ravb_main.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index c81cbd81826e..7a7f743a1fef 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2248,8 +2248,15 @@ static struct net_device_stats *ravb_get_stats(struct net_device *ndev)
 	struct ravb_private *priv = netdev_priv(ndev);
 	const struct ravb_hw_info *info = priv->info;
 	struct net_device_stats *nstats, *stats0, *stats1;
+	struct device *dev = &priv->pdev->dev;
 
 	nstats = &ndev->stats;
+
+	pm_runtime_get_noresume(dev);
+
+	if (!pm_runtime_active(dev))
+		goto out_rpm_put;
+
 	stats0 = &priv->stats[RAVB_BE];
 
 	if (info->tx_counters) {
@@ -2291,6 +2298,8 @@ static struct net_device_stats *ravb_get_stats(struct net_device *ndev)
 		nstats->rx_over_errors += stats1->rx_over_errors;
 	}
 
+out_rpm_put:
+	pm_runtime_put_noidle(dev);
 	return nstats;
 }
 
@@ -2358,6 +2367,9 @@ static int ravb_close(struct net_device *ndev)
 	if (info->nc_queues)
 		ravb_ring_free(ndev, RAVB_NC);
 
+	/* Update statistics. */
+	ravb_get_stats(ndev);
+
 	/* Set reset mode. */
 	return ravb_set_opmode(ndev, CCC_OPC_RESET);
 }
-- 
2.39.2