linux-kernel - [PATCH 2/2] net: mt7531: ensure all MACs are powered down before reset

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Date:   Sat, 20 Aug 2022 23:37:07 +0200
From:   Alexander Couzens <lynxis@...0.eu>
To:     Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Golle <daniel@...rotopia.org>, netdev@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Alexander Couzens <lynxis@...0.eu>
Subject: [PATCH 2/2] net: mt7531: ensure all MACs are powered down before reset

The datasheet [1] explicit describes it as requirement for a reset.

[1] MT7531 Reference Manual for Development Board rev 1.0, page 735

Signed-off-by: Alexander Couzens <lynxis@...0.eu>
---
 drivers/net/dsa/mt7530.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 95a57aeb466e..409d5c3d76ea 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -2329,6 +2329,10 @@ mt7531_setup(struct dsa_switch *ds)
 		return -ENODEV;
 	}
 
+	/* all MACs must be forced link-down before sw reset */
+	for (i = 0; i < MT7530_NUM_PORTS; i++)
+		mt7530_write(priv, MT7530_PMCR_P(i), MT7531_FORCE_LNK);
+
 	/* Reset the switch through internal reset */
 	mt7530_write(priv, MT7530_SYS_CTRL,
 		     SYS_CTRL_PHY_RST | SYS_CTRL_SW_RST |
-- 
2.35.1