genphy_read_status() cannot report correct link speed when BCM54616S PHY
is configured in RGMII->1000Base-KX mode (for example, on Facebook CMM
BMC platform), and it is because speed-related fields in MII registers
are assigned different meanings in 1000X register set. Actually there
is no speed field in 1000X register set because link speed is always
1000 Mb/s.

The patch adds "probe" callback to detect PHY's operation mode based on
INTERF_SEL[1:0] pins and 1000X/100FX selection bit in SerDES 100-FX
Control register. Besides, link speed is manually set to 1000 Mb/s in
"read_status" callback if PHY-switch link is 1000Base-X.

Signed-off-by: Tao Ren <tao...@fb.com>
---
 Changes in v3:
  - rename bcm5482_read_status to bcm54xx_read_status so the callback can
    be shared by BCM5482 and BCM54616S.
 Changes in v2:
  - Auto-detect PHY operation mode instead of passing DT node.
  - move PHY mode auto-detect logic from config_init to probe callback.
  - only set speed (not including duplex) in read_status callback.
  - update patch description with more background to avoid confusion.
  - patch #1 in the series ("net: phy: broadcom: set features explicitly
    for BCM54616") is dropped: the fix should go to get_features callback
    which may potentially depend on this patch.

 drivers/net/phy/broadcom.c | 41 +++++++++++++++++++++++++++++++++-----
 include/linux/brcmphy.h    | 10 ++++++++--
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
index 937d0059e8ac..ecad8a201a09 100644
--- a/drivers/net/phy/broadcom.c
+++ b/drivers/net/phy/broadcom.c
@@ -383,9 +383,9 @@ static int bcm5482_config_init(struct phy_device *phydev)
                /*
                 * Select 1000BASE-X register set (primary SerDes)
                 */
-               reg = bcm_phy_read_shadow(phydev, BCM5482_SHD_MODE);
-               bcm_phy_write_shadow(phydev, BCM5482_SHD_MODE,
-                                    reg | BCM5482_SHD_MODE_1000BX);
+               reg = bcm_phy_read_shadow(phydev, BCM54XX_SHD_MODE);
+               bcm_phy_write_shadow(phydev, BCM54XX_SHD_MODE,
+                                    reg | BCM54XX_SHD_MODE_1000BX);
 
                /*
                 * LED1=ACTIVITYLED, LED3=LINKSPD[2]
@@ -409,7 +409,7 @@ static int bcm5482_config_init(struct phy_device *phydev)
        return err;
 }
 
-static int bcm5482_read_status(struct phy_device *phydev)
+static int bcm54xx_read_status(struct phy_device *phydev)
 {
        int err;
 
@@ -464,6 +464,35 @@ static int bcm54616s_config_aneg(struct phy_device *phydev)
        return ret;
 }
 
+static int bcm54616s_probe(struct phy_device *phydev)
+{
+       int val, intf_sel;
+
+       val = bcm_phy_read_shadow(phydev, BCM54XX_SHD_MODE);
+       if (val < 0)
+               return val;
+
+       /* The PHY is strapped in RGMII to fiber mode when INTERF_SEL[1:0]
+        * is 01b.
+        */
+       intf_sel = (val & BCM54XX_SHD_INTF_SEL_MASK) >> 1;
+       if (intf_sel == 1) {
+               val = bcm_phy_read_shadow(phydev, BCM54616S_SHD_100FX_CTRL);
+               if (val < 0)
+                       return val;
+
+               /* Bit 0 of the SerDes 100-FX Control register, when set
+                * to 1, sets the MII/RGMII -> 100BASE-FX configuration.
+                * When this bit is set to 0, it sets the GMII/RGMII ->
+                * 1000BASE-X configuration.
+                */
+               if (!(val & BCM54616S_100FX_MODE))
+                       phydev->dev_flags |= PHY_BCM_FLAGS_MODE_1000BX;
+       }
+
+       return 0;
+}
+
 static int brcm_phy_setbits(struct phy_device *phydev, int reg, int set)
 {
        int val;
@@ -655,6 +684,8 @@ static struct phy_driver broadcom_drivers[] = {
        .config_aneg    = bcm54616s_config_aneg,
        .ack_interrupt  = bcm_phy_ack_intr,
        .config_intr    = bcm_phy_config_intr,
+       .read_status    = bcm54xx_read_status,
+       .probe          = bcm54616s_probe,
 }, {
        .phy_id         = PHY_ID_BCM5464,
        .phy_id_mask    = 0xfffffff0,
@@ -689,7 +720,7 @@ static struct phy_driver broadcom_drivers[] = {
        .name           = "Broadcom BCM5482",
        /* PHY_GBIT_FEATURES */
        .config_init    = bcm5482_config_init,
-       .read_status    = bcm5482_read_status,
+       .read_status    = bcm54xx_read_status,
        .ack_interrupt  = bcm_phy_ack_intr,
        .config_intr    = bcm_phy_config_intr,
 }, {
diff --git a/include/linux/brcmphy.h b/include/linux/brcmphy.h
index 6db2d9a6e503..b475e7f20d28 100644
--- a/include/linux/brcmphy.h
+++ b/include/linux/brcmphy.h
@@ -200,9 +200,15 @@
 #define BCM5482_SHD_SSD                0x14    /* 10100: Secondary SerDes 
control */
 #define BCM5482_SHD_SSD_LEDM   0x0008  /* SSD LED Mode enable */
 #define BCM5482_SHD_SSD_EN     0x0001  /* SSD enable */
-#define BCM5482_SHD_MODE       0x1f    /* 11111: Mode Control Register */
-#define BCM5482_SHD_MODE_1000BX        0x0001  /* Enable 1000BASE-X registers 
*/
 
+/* 10011: SerDes 100-FX Control Register */
+#define BCM54616S_SHD_100FX_CTRL       0x13
+#define        BCM54616S_100FX_MODE            BIT(0)  /* 100-FX SerDes Enable 
*/
+
+/* 11111: Mode Control Register */
+#define BCM54XX_SHD_MODE               0x1f
+#define BCM54XX_SHD_INTF_SEL_MASK      GENMASK(2, 1)   /* INTERF_SEL[1:0] */
+#define BCM54XX_SHD_MODE_1000BX                BIT(0)  /* Enable 1000-X 
registers */
 
 /*
  * EXPANSION SHADOW ACCESS REGISTERS.  (PHY REG 0x15, 0x16, and 0x17)
-- 
2.17.1

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