[PATCH net-next v4 5/6] net: ravb: Do not apply features to hardware if the interface is down

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

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

Do not apply features to hardware if the interface is down. In case runtime
PM is enabled, and while the interface is down, the IP will be in reset
mode (as for some platforms disabling the clocks will switch the IP to
reset mode, which will lead to losing register contents) and applying
settings in reset mode is not an option. Instead, cache the features and
apply them in ravb_open() through ravb_emac_init().

To avoid accessing the hardware while the interface is down
pm_runtime_active() check was introduced. Along with it the device runtime
PM usage counter has been incremented to avoid disabling the device clocks
while the check is in progress (if any).

Commit prepares for the addition of runtime PM.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
---

Changes in v4:
- simplified the code
- didn't collect the Sergey's tag as the code was changed

Changes in v3:
- updated patch title and description
- updated patch content due to patch 4/6

Changes in v2:
- fixed typo in patch description
- adjusted ravb_set_features_gbeth(); didn't collect the Sergey's Rb
  tag due to this 

Changes since [2]:
- use pm_runtime_get_noresume() and pm_runtime_active() and updated the
  commit message to describe that
- fixed typos
- s/CSUM/checksum in patch title and description

Changes in v3 of [2]:
- this was patch 20/21 in v2
- fixed typos in patch description
- removed code from ravb_open()
- use ndev->flags & IFF_UP checks instead of netif_running()

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

 drivers/net/ethernet/renesas/ravb_main.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index ac23779d1cc5..6f0677d1adee 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2564,9 +2564,18 @@ static int ravb_set_features(struct net_device *ndev,
 {
 	struct ravb_private *priv = netdev_priv(ndev);
 	const struct ravb_hw_info *info = priv->info;
+	struct device *dev = &priv->pdev->dev;
 	int ret;
 
-	ret = info->set_feature(ndev, features);
+	pm_runtime_get_noresume(dev);
+
+	if (pm_runtime_active(dev))
+		ret = info->set_feature(ndev, features);
+	else
+		ret = 0;
+
+	pm_runtime_put_noidle(dev);
+
 	if (ret)
 		return ret;
 
-- 
2.39.2