net: ravb: Make write access to CXR35 first before accessing other EMAC registers

stable inclusion
from stable-v6.6.5
commit 1a4fc93dfaa7b98fdf16550497206d4a7fe8e89b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8N21P

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a4fc93dfaa7b98fdf16550497206d4a7fe8e89b



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[ Upstream commit d78c0ced60d5e2f8b5a4a0468a5c400b24aeadf2 ]

Hardware manual of RZ/G3S (and RZ/G2L) specifies the following on the
description of CXR35 register (chapter "PHY interface select register
(CXR35)"): "After release reset, make write-access to this register before
making write-access to other registers (except MDIOMOD). Even if not need
to change the value of this register, make write-access to this register
at least one time. Because RGMII/MII MODE is recognized by accessing this
register".

The setup procedure for EMAC module (chapter "Setup procedure" of RZ/G3S,
RZ/G2L manuals) specifies the E-MAC.CXR35 register is the first EMAC
register that is to be configured.

Note [A] from chapter "PHY interface select register (CXR35)" specifies
the following:
[A] The case which CXR35 SEL_XMII is used for the selection of RGMII/MII
in APB Clock 100 MHz.
(1) To use RGMII interface, Set ‘H’03E8_0000’ to this register.
(2) To use MII interface, Set ‘H’03E8_0002’ to this register.

Take into account these indication.

Fixes: 1089877a ("ravb: Add RZ/G2L MII interface support")
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>