Re: [PATCH RFC net-next 1/2] net: pcs: xpcs: Add special code to operate in Microchip KSZ9477 switch

["Russell King (Oracle)" <linux@armlinux.org.uk>]

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On Thu, Jan 30, 2025 at 12:44:54PM +0000, Russell King (Oracle) wrote:
> @@ -1123,7 +1126,9 @@ static void xpcs_link_up_sgmii_1000basex(struct dw_xpcs *xpcs,
>  {
>  	int ret;
>  
> -	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED)
> +	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED &&
> +	    !(interface == PHY_INTERFACE_MODE_SGMII &&
> +	      xpcs->sgmii_mode == )
                                  ^ DW_XPCS_SGMII_MODE_MAC_MANUAL

Not sure where that went. :(

>  		return;
>  
>  	if (interface == PHY_INTERFACE_MODE_1000BASEX) {

Note that with this change, we also need to change the xpcs_write() to
BMCR at the end of this function to xpcs_modify() so we don't clear the
AN-enable bit. It's also a good idea in general to only modify the bits
we need to modify.

New patch attached.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

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From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Subject: [PATCH net-next] net: xpcs: add support for manual update for SGMII

Older revisions of the XPCS IP do not support the MAC_AUTO_SW flag and
need the BMCR register updated with the speed information from the PHY.
Split the DW_XPCS_SGMII_MODE_MAC mode into _AUTO and _MANUAL variants,
where _AUTO mode means the update happens in hardware autonomously,
whereas the _MANUAL mode means that we need to update the BMCR register
when the link comes up.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/pcs/pcs-xpcs.c | 16 +++++++++++-----
 drivers/net/pcs/pcs-xpcs.h | 11 ++++++++---
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index e7aad3c402a4..29269d5c5f3a 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -691,11 +691,14 @@ static int xpcs_config_aneg_c37_sgmii(struct dw_xpcs *xpcs,
 	mask = DW_VR_MII_DIG_CTRL1_2G5_EN | DW_VR_MII_DIG_CTRL1_MAC_AUTO_SW;
 
 	switch (xpcs->sgmii_mode) {
-	case DW_XPCS_SGMII_MODE_MAC:
+	case DW_XPCS_SGMII_MODE_MAC_AUTO:
 		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED)
 			val = DW_VR_MII_DIG_CTRL1_MAC_AUTO_SW;
 		break;
 
+	case DW_XPCS_SGMII_MODE_MAC_MANUAL:
+		break;
+
 	case DW_XPCS_SGMII_MODE_PHY_HW:
 		val |= DW_VR_MII_DIG_CTRL1_PHY_MODE_CTRL;
 		fallthrough;
@@ -1123,7 +1126,9 @@ static void xpcs_link_up_sgmii_1000basex(struct dw_xpcs *xpcs,
 {
 	int ret;
 
-	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED)
+	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED &&
+	    !(interface == PHY_INTERFACE_MODE_SGMII &&
+	      xpcs->sgmii_mode == DW_XPCS_SGMII_MODE_MAC_MANUAL)
 		return;
 
 	if (interface == PHY_INTERFACE_MODE_1000BASEX) {
@@ -1140,10 +1145,11 @@ static void xpcs_link_up_sgmii_1000basex(struct dw_xpcs *xpcs,
 				__func__);
 	}
 
-	ret = xpcs_write(xpcs, MDIO_MMD_VEND2, MII_BMCR,
-			 mii_bmcr_encode_fixed(speed, duplex));
+	ret = xpcs_modify(xpcs, MDIO_MMD_VEND2, MII_BMCR,
+			  BMCR_SPEED1000 | BMCR_FULLDPLX | BMCR_SPEED100,
+			  mii_bmcr_encode_fixed(speed, duplex));
 	if (ret)
-		dev_err(&xpcs->mdiodev->dev, "%s: xpcs_write returned %pe\n",
+		dev_err(&xpcs->mdiodev->dev, "%s: xpcs_modify returned %pe\n",
 			__func__, ERR_PTR(ret));
 }
 
diff --git a/drivers/net/pcs/pcs-xpcs.h b/drivers/net/pcs/pcs-xpcs.h
index 4bd6a82f1a18..be8fab40b012 100644
--- a/drivers/net/pcs/pcs-xpcs.h
+++ b/drivers/net/pcs/pcs-xpcs.h
@@ -112,8 +112,12 @@ enum dw_xpcs_sgmii_10_100 {
 };
 
 /* The SGMII mode:
- * DW_XPCS_SGMII_MODE_MAC: the XPCS acts as a MAC, reading and acknowledging
- * the config word.
+ * DW_XPCS_SGMII_MODE_MAC_AUTO: the XPCS acts as a MAC, accepting the
+ * parameters from the PHY end of the SGMII link and acknowledging the
+ * config word. The XPCS autonomously switches speed.
+ *
+ * DW_XPCS_SGMII_MODE_MAC_MANUAL: the XPCS acts as a MAC as above, but
+ * does not autonomously switch speed.
  *
  * DW_XPCS_SGMII_MODE_PHY_HW: the XPCS acts as a PHY, deriving the tx_config
  * bits 15 (link), 12 (duplex) and 11:10 (speed) from hardware inputs to the
@@ -125,7 +129,8 @@ enum dw_xpcs_sgmii_10_100 {
  * integration documentation states that MII_ADVERTISE must be written last.
  */
 enum dw_xpcs_sgmii_mode {
-	DW_XPCS_SGMII_MODE_MAC,		/* XPCS is MAC on SGMII */
+	DW_XPCS_SGMII_MODE_MAC_AUTO,	/* XPCS is MAC, auto update */
+	DW_XPCS_SGMII_MODE_MAC_MANUAL,	/* XPCS is MAC, manual update */
 	DW_XPCS_SGMII_MODE_PHY_HW,	/* XPCS is PHY, tx_config from hw */
 	DW_XPCS_SGMII_MODE_PHY_REG,	/* XPCS is PHY, tx_config from regs */
 };
-- 
2.30.2