netdev - [PATCH net-next v2 1/5] net: mediatek: sgmii: fix powering up the SGMII phy

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Date:   Mon, 19 Sep 2022 10:37:08 +0200
From:   Alexander Couzens <lynxis@...0.eu>
To:     Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     Daniel Golle <daniel@...rotopia.org>,
        Alexander Couzens <lynxis@...0.eu>, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next v2 1/5] net: mediatek: sgmii: fix powering up the SGMII phy

There are cases when the SGMII_PHYA_PWD register contains 0x9 which
prevents SGMII from working. The SGMII still shows link but no traffic
can flow. Writing 0x0 to the PHYA_PWD register fix the issue. 0x0 was
taken from a good working state of the SGMII interface.

Signed-off-by: Alexander Couzens <lynxis@...0.eu>
---
 drivers/net/ethernet/mediatek/mtk_sgmii.c | 25 ++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_sgmii.c b/drivers/net/ethernet/mediatek/mtk_sgmii.c
index 736839c84130..b9b15e1a292c 100644
--- a/drivers/net/ethernet/mediatek/mtk_sgmii.c
+++ b/drivers/net/ethernet/mediatek/mtk_sgmii.c
@@ -36,9 +36,15 @@ static int mtk_pcs_setup_mode_an(struct mtk_pcs *mpcs)
 	val |= SGMII_AN_RESTART;
 	regmap_write(mpcs->regmap, SGMSYS_PCS_CONTROL_1, val);
 
-	regmap_read(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, &val);
-	val &= ~SGMII_PHYA_PWD;
-	regmap_write(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, val);
+	/* Release PHYA power down state
+	 * Only removing bit SGMII_PHYA_PWD isn't enough.
+	 * There are cases when the SGMII_PHYA_PWD register contains 0x9 which
+	 * prevents SGMII from working. The SGMII still shows link but no traffic
+	 * can flow. Writing 0x0 to the PHYA_PWD register fix the issue. 0x0 was
+	 * taken from a good working state of the SGMII interface.
+	 * Tested on mt7622 & mt7986.
+	 */
+	regmap_write(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, 0);
 
 	return 0;
 
@@ -69,10 +75,15 @@ static int mtk_pcs_setup_mode_force(struct mtk_pcs *mpcs,
 	val |= SGMII_SPEED_1000;
 	regmap_write(mpcs->regmap, SGMSYS_SGMII_MODE, val);
 
-	/* Release PHYA power down state */
-	regmap_read(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, &val);
-	val &= ~SGMII_PHYA_PWD;
-	regmap_write(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, val);
+	/* Release PHYA power down state
+	 * Only removing bit SGMII_PHYA_PWD isn't enough.
+	 * There are cases when the SGMII_PHYA_PWD register contains 0x9 which
+	 * prevents SGMII from working. The SGMII still shows link but no traffic
+	 * can flow. Writing 0x0 to the PHYA_PWD register fix the issue. 0x0 was
+	 * taken from a good working state of the SGMII interface.
+	 * Tested on mt7622 & mt7986.
+	 */
+	regmap_write(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, 0);
 
 	return 0;
 }
-- 
2.37.3