[net-next,PATCH] net: stmmac: stm32: Do not suspend downed interface

[Marek Vasut <marex@nabladev.com>]

If an interface is down, the ETHnSTP clock are not running. Suspending
such an interface will attempt to stop already stopped ETHnSTP clock,
and produce a warning in the kernel log about this.

STM32MP25xx that is booted from NFS root via its first ethernet MAC
(also the consumer of ck_ker_eth1stp) and with its second ethernet
MAC downed produces the following warnings during suspend resume
cycle. This can be provoked even using pm_test:

"
$ echo devices > /sys/power/pm_test
$ echo mem > /sys/power/state
...
ck_ker_eth2stp already disabled
...
ck_ker_eth2stp already unprepared
...
"

Fix this by not manipulating with the clock during suspend resume
of interfaces which are downed.

Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: Christophe Roullier <christophe.roullier@st.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: kernel@dh-electronics.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: netdev@vger.kernel.org
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
index e1b260ed4790b..5b0d111afcac3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
@@ -618,11 +618,21 @@ static void stm32_dwmac_remove(struct platform_device *pdev)
 
 static int stm32mp1_suspend(struct stm32_dwmac *dwmac)
 {
+	struct net_device *ndev = dev_get_drvdata(dwmac->dev);
+
+	if (!ndev || !netif_running(ndev))
+		return 0;
+
 	return clk_prepare_enable(dwmac->clk_ethstp);
 }
 
 static void stm32mp1_resume(struct stm32_dwmac *dwmac)
 {
+	struct net_device *ndev = dev_get_drvdata(dwmac->dev);
+
+	if (!ndev || !netif_running(ndev))
+		return;
+
 	clk_disable_unprepare(dwmac->clk_ethstp);
 }
 
-- 
2.51.0