netdev - [PATCH v3 net 1/3] net: mediatek: sgmii: ensure the SGMII PHY is powered down on configuration

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Date:   Sun, 22 Jan 2023 22:21:51 +0100
From:   Bjørn Mork <bjorn@...k.no>
To:     netdev@...r.kernel.org
Cc:     Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Daniel Golle <daniel@...rotopia.org>,
        Alexander Couzens <lynxis@...0.eu>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Bjørn Mork <bjorn@...k.no>
Subject: [PATCH v3 net 1/3] net: mediatek: sgmii: ensure the SGMII PHY is powered down on configuration

From: Alexander Couzens <lynxis@...0.eu>

The code expect the PHY to be in power down which is only true after reset.
Allow changes of the SGMII parameters more than once.

Only power down when reconfiguring to avoid bouncing the link when there's
no reason to - based on code from Russell King.

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.

Suggested-by: Russell King (Oracle) <linux@...linux.org.uk>
Signed-off-by: Alexander Couzens <lynxis@...0.eu>
[ bmork: rebased and squashed into one patch ]
Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Bjørn Mork <bjorn@...k.no>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.h |  2 ++
 drivers/net/ethernet/mediatek/mtk_sgmii.c   | 39 +++++++++++++++------
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.h b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
index dff0e3ad2de6..70e729468a95 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
@@ -1067,11 +1067,13 @@ struct mtk_soc_data {
  *                     SGMII modes
  * @ana_rgc3:          The offset refers to register ANA_RGC3 related to regmap
  * @pcs:               Phylink PCS structure
+ * @interface:         Currently configured interface mode
  */
 struct mtk_pcs {
 	struct regmap	*regmap;
 	u32             ana_rgc3;
 	struct phylink_pcs pcs;
+	phy_interface_t	interface;
 };
 
 /* struct mtk_sgmii -  This is the structure holding sgmii regmap and its
diff --git a/drivers/net/ethernet/mediatek/mtk_sgmii.c b/drivers/net/ethernet/mediatek/mtk_sgmii.c
index 5c286f2c9418..0a06995099cf 100644
--- a/drivers/net/ethernet/mediatek/mtk_sgmii.c
+++ b/drivers/net/ethernet/mediatek/mtk_sgmii.c
@@ -43,11 +43,6 @@ static int mtk_pcs_config(struct phylink_pcs *pcs, unsigned int mode,
 	int advertise, link_timer;
 	bool changed, use_an;
 
-	if (interface == PHY_INTERFACE_MODE_2500BASEX)
-		rgc3 = RG_PHY_SPEED_3_125G;
-	else
-		rgc3 = 0;
-
 	advertise = phylink_mii_c22_pcs_encode_advertisement(interface,
 							     advertising);
 	if (advertise < 0)
@@ -88,9 +83,22 @@ static int mtk_pcs_config(struct phylink_pcs *pcs, unsigned int mode,
 		bmcr = 0;
 	}
 
-	/* Configure the underlying interface speed */
-	regmap_update_bits(mpcs->regmap, mpcs->ana_rgc3,
-			   RG_PHY_SPEED_3_125G, rgc3);
+	if (mpcs->interface != interface) {
+		/* PHYA power down */
+		regmap_update_bits(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL,
+				   SGMII_PHYA_PWD, SGMII_PHYA_PWD);
+
+		if (interface == PHY_INTERFACE_MODE_2500BASEX)
+			rgc3 = RG_PHY_SPEED_3_125G;
+		else
+			rgc3 = 0;
+
+		/* Configure the underlying interface speed */
+		regmap_update_bits(mpcs->regmap, mpcs->ana_rgc3,
+				   RG_PHY_SPEED_3_125G, rgc3);
+
+		mpcs->interface = interface;
+	}
 
 	/* Update the advertisement, noting whether it has changed */
 	regmap_update_bits_check(mpcs->regmap, SGMSYS_PCS_ADVERTISE,
@@ -108,9 +116,17 @@ static int mtk_pcs_config(struct phylink_pcs *pcs, unsigned int mode,
 	regmap_update_bits(mpcs->regmap, SGMSYS_PCS_CONTROL_1,
 			   SGMII_AN_RESTART | SGMII_AN_ENABLE, bmcr);
 
-	/* Release PHYA power down state */
-	regmap_update_bits(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL,
-			   SGMII_PHYA_PWD, 0);
+	/* 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.
+	 * Unknown how much the QPHY needs but it is racy without a sleep.
+	 * Tested on mt7622 & mt7986.
+	 */
+	usleep_range(50, 100);
+	regmap_write(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL, 0);
 
 	return changed;
 }
@@ -171,6 +187,7 @@ int mtk_sgmii_init(struct mtk_sgmii *ss, struct device_node *r, u32 ana_rgc3)
 			return PTR_ERR(ss->pcs[i].regmap);
 
 		ss->pcs[i].pcs.ops = &mtk_pcs_ops;
+		ss->pcs[i].interface = PHY_INTERFACE_MODE_NA;
 	}
 
 	return 0;
-- 
2.30.2