linux-kernel - [PATCH net] net: mdio: mdio-bcm-unimac: Correct rate fallback logic

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Message-Id: <20250729213148.3403882-1-florian.fainelli@broadcom.com>
Date: Tue, 29 Jul 2025 14:31:48 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: netdev@...r.kernel.org
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	Doug Berger <opendmb@...il.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Jacob Keller <jacob.e.keller@...el.com>,
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH net] net: mdio: mdio-bcm-unimac: Correct rate fallback logic

In case the rate for the parent clock is zero, make sure that we still
fallback to using a fixed rate for the divider calculation, otherwise we
simply ignore the desired MDIO bus clock frequency which can prevent us
from interfacing with Ethernet PHYs properly.

Fixes: ee975351cf0c ("net: mdio: mdio-bcm-unimac: Manage clock around I/O accesses")
Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
---
 drivers/net/mdio/mdio-bcm-unimac.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/mdio/mdio-bcm-unimac.c b/drivers/net/mdio/mdio-bcm-unimac.c
index b6e30bdf5325..9c0a11316cfd 100644
--- a/drivers/net/mdio/mdio-bcm-unimac.c
+++ b/drivers/net/mdio/mdio-bcm-unimac.c
@@ -209,10 +209,9 @@ static int unimac_mdio_clk_set(struct unimac_mdio_priv *priv)
 	if (ret)
 		return ret;
 
-	if (!priv->clk)
+	rate = clk_get_rate(priv->clk);
+	if (!priv->clk || !rate)
 		rate = 250000000;
-	else
-		rate = clk_get_rate(priv->clk);
 
 	div = (rate / (2 * priv->clk_freq)) - 1;
 	if (div & ~MDIO_CLK_DIV_MASK) {
-- 
2.34.1