net: pcs: rzn1-miic: Correct MODCTRL register offset
Correct the Mode Control Register (MODCTRL) offset for RZ/N MIIC.
According to the R-IN Engine and Ethernet Peripherals Manual (Rev.1.30)
[0], Table 10.1 "Ethernet Accessory Register List", MODCTRL is at offset
0x8, not 0x20 as previously defined.
Offset 0x20 actually maps to the Port Trigger Control Register (PTCTRL),
which controls PTP_MODE[3:0] and RGMII_CLKSEL[4]. Using this incorrect
definition prevented the driver from configuring the SW_MODE[4:0] bits
in MODCTRL, which control the internal connection of Ethernet ports. As
a result, the MIIC could not be switched into the correct mode, leading
to link setup failures and non-functional Ethernet ports on affected
systems.
[0] https://www.renesas.com/en/document/mah/rzn1d-group-rzn1s-group-rzn1l-group-users-manual-r-engine-and-ethernet-peripherals?r=1054571
Fixes: 7dc54d3b8d91 ("net: pcs: add Renesas MII converter driver")
Cc: stable@kernel.org
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://patch.msgid.link/20250901112019.16278-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/drivers/net/pcs/pcs-rzn1-miic.c b/drivers/net/pcs/pcs-rzn1-miic.c
index d79bb9b..ce73d94 100644
--- a/drivers/net/pcs/pcs-rzn1-miic.c
+++ b/drivers/net/pcs/pcs-rzn1-miic.c
@@ -19,7 +19,7 @@
#define MIIC_PRCMD 0x0
#define MIIC_ESID_CODE 0x4
-#define MIIC_MODCTRL 0x20
+#define MIIC_MODCTRL 0x8
#define MIIC_MODCTRL_SW_MODE GENMASK(4, 0)
#define MIIC_CONVCTRL(port) (0x100 + (port) * 4)
