linux-kernel - [net-next: PATCH v7 4/7] dsa: lan9303: write reg only if necessary

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Message-ID: <20230117205703.25960-5-jerry.ray@microchip.com>
Date:   Tue, 17 Jan 2023 14:57:00 -0600
From:   Jerry Ray <jerry.ray@...rochip.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "Paolo Abeni" <pabeni@...hat.com>,
        Russell King <linux@...linux.org.uk>, <jbe@...gutronix.de>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Jerry Ray <jerry.ray@...rochip.com>
Subject: [net-next: PATCH v7 4/7] dsa: lan9303: write reg only if necessary

As the regmap_write() is over a slow bus that will sleep, we can speed up
the boot-up time a bit by not bothering to clear a bit that is already
clear.

Signed-off-by: Jerry Ray <jerry.ray@...rochip.com>
---
 drivers/net/dsa/lan9303-core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/lan9303-core.c b/drivers/net/dsa/lan9303-core.c
index 66466d50d015..a4decf42a002 100644
--- a/drivers/net/dsa/lan9303-core.c
+++ b/drivers/net/dsa/lan9303-core.c
@@ -915,8 +915,11 @@ static int lan9303_setup(struct dsa_switch *ds)
 	if (ret)
 		return (ret);
 
-	reg &= ~LAN9303_VIRT_SPECIAL_TURBO;
-	regmap_write(chip->regmap, LAN9303_VIRT_SPECIAL_CTRL, reg);
+	/* Clear the TURBO Mode bit if it was set. */
+	if (reg & LAN9303_VIRT_SPECIAL_TURBO) {
+		reg &= ~LAN9303_VIRT_SPECIAL_TURBO;
+		regmap_write(chip->regmap, LAN9303_VIRT_SPECIAL_CTRL, reg);
+	}
 
 	ret = lan9303_setup_tagging(chip);
 	if (ret)
-- 
2.17.1