linux-kernel - [PATCH net v3 4/5] net: dsa: vsc73xx: allow phy resetting

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Message-Id: <20240809193807.2221897-5-paweldembicki@gmail.com>
Date: Fri,  9 Aug 2024 21:38:05 +0200
From: Pawel Dembicki <paweldembicki@...il.com>
To: netdev@...r.kernel.org
Cc: Pawel Dembicki <paweldembicki@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	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>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: [PATCH net v3 4/5] net: dsa: vsc73xx: allow phy resetting

Resetting the VSC73xx PHY was problematic because the MDIO bus, without
a busy check, read and wrote incorrect register values.

My investigation indicates that resetting the PHY only triggers changes
in configuration. However, improper register values written earlier
were only exposed after a soft reset.

The reset itself wasn't the issue; rather, the problem stemmed from
incorrect read and write operations.

A 'soft_reset' can now proceed normally. There are no reasons to keep
the VSC73xx from being reset.

This commit removes the reset blockade in the 'vsc73xx_phy_write'
function.

Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
Signed-off-by: Pawel Dembicki <paweldembicki@...il.com>
---
v3:
  - resend only
v2:
  - improved commit description

This patch came from net-next series[0].
Changes since net-next:
  - rebased to netdev/main only

[0] https://patchwork.kernel.org/project/netdevbpf/patch/20240729210615.279952-6-paweldembicki@gmail.com/
---
 drivers/net/dsa/vitesse-vsc73xx-core.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index a789b2da9b7d..e3f95d2cc2c1 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -598,17 +598,6 @@ static int vsc73xx_phy_write(struct dsa_switch *ds, int phy, int regnum,
 	if (ret)
 		return ret;
 
-	/* It was found through tedious experiments that this router
-	 * chip really hates to have it's PHYs reset. They
-	 * never recover if that happens: autonegotiation stops
-	 * working after a reset. Just filter out this command.
-	 * (Resetting the whole chip is OK.)
-	 */
-	if (regnum == 0 && (val & BIT(15))) {
-		dev_info(vsc->dev, "reset PHY - disallowed\n");
-		return 0;
-	}
-
 	cmd = (phy << 21) | (regnum << 16) | val;
 	ret = vsc73xx_write(vsc, VSC73XX_BLOCK_MII, 0, 1, cmd);
 	if (ret)
-- 
2.34.1