[PATCH] drivers: ethernet: cpsw: fix panic when interrupt coaleceing is set via ethtool

["Sondhauß, Jan" <Jan.Sondhauss@wago.com>]

cpsw_ethtool uses the power management in the begin and complete
functions of the ethtool_ops. The result of pm_runtime_get_sync was
returned unconditionally, which results in problems since the ethtool-
interface relies on 0 for success and negativ values for errors.
d43c65b05b84 (ethtool: runtime-resume netdev parent in ethnl_ops_begin)
introduced power management to the netlink implementation for the
ethtool interface and does not explicitly check for negative return
values.

As a result the pm_runtime_suspend function is called one-too-many
times in ethnl_ops_begin and that leads to an access violation when
the cpsw hardware is accessed after using
'ethtool -C eth-of-cpsw rx-usecs 1234'. To fix this the call to
pm_runtime_get_sync in cpsw_ethtool_op_begin is replaced with a call
to pm_runtime_resume_and_get as it provides a returnable error-code.

Signed-off-by: Jan Sondhauss <jan.sondhauss@wago.com>
---
 drivers/net/ethernet/ti/cpsw_ethtool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/cpsw_ethtool.c b/drivers/net/ethernet/ti/cpsw_ethtool.c
index 158c8d3793f4..5eda20039cc1 100644
--- a/drivers/net/ethernet/ti/cpsw_ethtool.c
+++ b/drivers/net/ethernet/ti/cpsw_ethtool.c
@@ -364,7 +364,7 @@ int cpsw_ethtool_op_begin(struct net_device *ndev)
 	struct cpsw_common *cpsw = priv->cpsw;
 	int ret;
 
-	ret = pm_runtime_get_sync(cpsw->dev);
+	ret = pm_runtime_resume_and_get(cpsw->dev);
 	if (ret < 0) {
 		cpsw_err(priv, drv, "ethtool begin failed %d\n", ret);
 		pm_runtime_put_noidle(cpsw->dev);
-- 
2.35.1