[PATCH 3/9] net/ngbe: fix occasional failure of reading PHY ID

[Jiawen Wu <jiawenwu@trustnetic.com>]

Change to check low ID register to determine the valid PHY address,
for yt8521s PHY with high ID register value 0. And fix polling
register when expect value is 0, to complete MDIO read.

Fixes: 44e97550ca68 ("net/ngbe: identify and reset PHY")
Cc: stable@dpdk.org

Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
---
 drivers/net/ngbe/base/ngbe_phy.c  | 7 ++-----
 drivers/net/ngbe/base/ngbe_regs.h | 9 +++++++--
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ngbe/base/ngbe_phy.c b/drivers/net/ngbe/base/ngbe_phy.c
index 8199696428..1025d7d3a1 100644
--- a/drivers/net/ngbe/base/ngbe_phy.c
+++ b/drivers/net/ngbe/base/ngbe_phy.c
@@ -120,17 +120,14 @@ bool ngbe_validate_phy_addr(struct ngbe_hw *hw, u32 phy_addr)
 	u16 phy_id = 0;
 	bool valid = false;
 
-	if (hw->sub_device_id == NGBE_SUB_DEV_ID_EM_YT8521S_SFP)
-		return true;
-
 	hw->phy.addr = phy_addr;
-	hw->phy.read_reg(hw, NGBE_MD_PHY_ID_HIGH,
+	hw->phy.read_reg(hw, NGBE_MD_PHY_ID_LOW,
 			     NGBE_MD_DEV_PMA_PMD, &phy_id);
 
 	if (phy_id != 0xFFFF && phy_id != 0x0)
 		valid = true;
 
-	DEBUGOUT("PHY ID HIGH is 0x%04X", phy_id);
+	DEBUGOUT("PHY ID LOW is 0x%04X", phy_id);
 
 	return valid;
 }
diff --git a/drivers/net/ngbe/base/ngbe_regs.h b/drivers/net/ngbe/base/ngbe_regs.h
index 6432ad8736..640e385990 100644
--- a/drivers/net/ngbe/base/ngbe_regs.h
+++ b/drivers/net/ngbe/base/ngbe_regs.h
@@ -1422,8 +1422,13 @@ po32m(struct ngbe_hw *hw, u32 reg, u32 mask, u32 expect, u32 *actual,
 	}
 
 	do {
-		all |= rd32(hw, reg);
-		value |= mask & all;
+		if (expect != 0) {
+			all |= rd32(hw, reg);
+			value |= mask & all;
+		} else {
+			all = rd32(hw, reg);
+			value = mask & all;
+		}
 		if (value == expect)
 			break;
 
-- 
2.27.0