[PATCH net v4] net: phy: meson-gxl: implement meson_gxl_phy_resume()

[Luke Lu]

From: Da Xue <da@libre.computer>

While testing the suspend/resume function, we found the ethernet
is broken if using internal PHY of Amlogic meson GXL SoC.
After system resume back, the ethernet is down, no carrier found.

	eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state
		DOWN group default qlen 1000

In this patch, we re-initialize the internal PHY to fix this problem.

	eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
		group default qlen 1000

Fixes: 7334b3e47aee ("net: phy: Add Meson GXL Internal PHY driver")
Signed-off-by: Da Xue <da@libre.computer>
Signed-off-by: Luke Lu <luke.lu@libre.computer>

---
Note, we don't Cc stable kernel tree in this patch intentionally, since
there will be a cherry-pick failure if apply this patch from kernel version
less than v6.2, it's not a logic failure but due to the changes too close.

Please check commit 69ff53e4a4c9 ("net: phy: meson-gxl: use MMD access dummy stubs for GXL, internal PHY")
We plan to slightly rework the patch, and send it to stable tree separately
once this patch is accepted into mainline.

v4:
 - refactor commit message to better explain the problem & fix
 - check return value of genphy_resume()
 - add 'net' annotation
 - add Fixes tag

v3: https://lore.kernel.org/netdev/20230808050016.1911447-1-da@libre.computer
 - fix missing parameter of genphy_resume()

v2: https://lore.kernel.org/netdev/20230804201903.1303713-1-da@libre.computer
 - call generic genphy_resume()

v1: https://lore.kernel.org/all/CACqvRUZRyXTVQyy9bUviQZ+_moLQBjPc6nin_NQC+CJ37yNnLw@xxxxxxxxxxxxxx
---
 drivers/net/phy/meson-gxl.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/meson-gxl.c b/drivers/net/phy/meson-gxl.c
index bb9b33b6bce2..9ebe09b0cd8c 100644
--- a/drivers/net/phy/meson-gxl.c
+++ b/drivers/net/phy/meson-gxl.c
@@ -132,6 +132,21 @@ static int meson_gxl_config_init(struct phy_device *phydev)
 	return 0;
 }
 
+static int meson_gxl_phy_resume(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = genphy_resume(phydev);
+	if (ret)
+		return ret;
+
+	ret = meson_gxl_config_init(phydev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
 /* This function is provided to cope with the possible failures of this phy
  * during aneg process. When aneg fails, the PHY reports that aneg is done
  * but the value found in MII_LPA is wrong:
@@ -196,7 +211,7 @@ static struct phy_driver meson_gxl_phy[] = {
 		.config_intr	= smsc_phy_config_intr,
 		.handle_interrupt = smsc_phy_handle_interrupt,
 		.suspend        = genphy_suspend,
-		.resume         = genphy_resume,
+		.resume         = meson_gxl_phy_resume,
 		.read_mmd	= genphy_read_mmd_unsupported,
 		.write_mmd	= genphy_write_mmd_unsupported,
 	}, {
-- 
2.40.1