[PATCH v2] net: macb: check return value of clk_prepare_enable() in runtime resume

[Gustavo Kenji Mendonça Kaneko]

macb_runtime_resume() calls clk_prepare_enable() five times but discards
the return value each time. clk_prepare_enable() is marked __must_check,
and if a clock fails to enable the driver would silently continue with
potentially unclocked hardware.

The symmetric disable path, macb_clks_disable(), already uses
clk_bulk_disable_unprepare(). Convert the enable path to the matching
clk_bulk_prepare_enable(), which enables the clocks as a group and, on
failure, unwinds the ones it already enabled before returning the error.

This was found by code review, not by an observed failure, and I do not
have macb hardware to test on; it is a robustness fix that propagates the
clk_prepare_enable() error instead of discarding it.

Signed-off-by: Gustavo Kenji Mendonça Kaneko <kaneko.dev@xxxxx>
---
v2:
 - Reword the commit message: drop the misleading "atomically" wording
   (there is no locking involved) and describe this as a robustness fix
   found by code review rather than a fix for an observed bug.
 - Cc the networking maintainers that were missing from v1.

 drivers/net/ethernet/cadence/macb_main.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index a12aa21244e8..85bd4ff0e4e6 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -6185,16 +6185,19 @@ static int __maybe_unused macb_runtime_resume(struct device *dev)
 {
 	struct net_device *netdev = dev_get_drvdata(dev);
 	struct macb *bp = netdev_priv(netdev);
+	struct clk_bulk_data clks[] = {
+		{ .clk = bp->pclk },
+		{ .clk = bp->hclk },
+		{ .clk = bp->tx_clk },
+		{ .clk = bp->rx_clk },
+		{ .clk = bp->tsu_clk },
+	};
 
-	if (!(device_may_wakeup(dev))) {
-		clk_prepare_enable(bp->pclk);
-		clk_prepare_enable(bp->hclk);
-		clk_prepare_enable(bp->tx_clk);
-		clk_prepare_enable(bp->rx_clk);
-		clk_prepare_enable(bp->tsu_clk);
-	} else if (!(bp->caps & MACB_CAPS_NEED_TSUCLK)) {
-		clk_prepare_enable(bp->tsu_clk);
-	}
+	if (!(device_may_wakeup(dev)))
+		return clk_bulk_prepare_enable(ARRAY_SIZE(clks), clks);
+
+	if (!(bp->caps & MACB_CAPS_NEED_TSUCLK))
+		return clk_prepare_enable(bp->tsu_clk);
 
 	return 0;
 }
-- 
2.54.0