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Message-ID: <20260107085708.936-1-javen_xu@realsil.com.cn>
Date: Wed, 7 Jan 2026 16:57:08 +0800
From: javen <javen_xu@...lsil.com.cn>
To: <hkallweit1@...il.com>
CC: <andrew+netdev@...n.ch>, <davem@...emloft.net>, <edumazet@...gle.com>,
<horms@...nel.org>, <javen_xu@...lsil.com.cn>, <kuba@...nel.org>,
<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
<nic_swsd@...ltek.com>, <pabeni@...hat.com>
Subject: RE: [PATCH net-next 2/2] r8169: enable LTR support
We generally do not recommend disabling LTR. LTR works in concert
with ASPM to reduce power consumption while maintaining performance.
There is no LTR-related bug in the existing code. The issue observed
on the customer’s evaluation platform is that the link cannot enter
L1.1/L1.2 without LTR support. This patch enables LTR to allow the
device and platform to reach those low power states. Therefore, this
patch should be considered as a new feature.
After a hardware reset, LTR Enable defaults to 0 (disabled). Driver
must program the related registers to enable LTR.
We will replace some register numbers with names according to the
datasheet in the next patch.
> > Signed-off-by: Javen Xu <javen_xu@...lsil.com.cn>
> > ---
> > drivers/net/ethernet/realtek/r8169_main.c | 98
> > +++++++++++++++++++++++
> > 1 file changed, 98 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/realtek/r8169_main.c
> > b/drivers/net/ethernet/realtek/r8169_main.c
> > index f9df6aadacce..97abf95502dc 100644
> > --- a/drivers/net/ethernet/realtek/r8169_main.c
> > +++ b/drivers/net/ethernet/realtek/r8169_main.c
> > @@ -2919,6 +2919,101 @@ static void rtl_disable_exit_l1(struct rtl8169_private *tp)
> > }
> > }
> >
> > +static void rtl_enable_ltr(struct rtl8169_private *tp) {
> > + switch (tp->mac_version) {
> > + case RTL_GIGA_MAC_VER_80:
> > + r8168_mac_ocp_write(tp, 0xcdd0, 0x9003);
> > + r8168_mac_ocp_modify(tp, 0xe034, 0x0000, 0xc000);
> > + r8168_mac_ocp_modify(tp, 0xe0a2, 0x0000, BIT(0));
> > + r8168_mac_ocp_write(tp, 0xcdd2, 0x8c09);
> > + r8168_mac_ocp_write(tp, 0xcdd8, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd4, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdda, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd6, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcddc, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcde8, 0x887a);
> > + r8168_mac_ocp_write(tp, 0xcdea, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdec, 0x8c09);
> > + r8168_mac_ocp_write(tp, 0xcdee, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdf0, 0x8a62);
> > + r8168_mac_ocp_write(tp, 0xcdf2, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdf4, 0x883e);
> > + r8168_mac_ocp_write(tp, 0xcdf6, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdf8, 0x8849);
> > + r8168_mac_ocp_write(tp, 0xcdfa, 0x9003);
> > + r8168_mac_ocp_modify(tp, 0xe032, 0x0000, BIT(14));
> > + break;
> > + case RTL_GIGA_MAC_VER_70:
> > + r8168_mac_ocp_write(tp, 0xcdd0, 0x9003);
> > + r8168_mac_ocp_modify(tp, 0xe034, 0x0000, 0xc000);
> > + r8168_mac_ocp_modify(tp, 0xe0a2, 0x0000, BIT(0));
> > + r8168_mac_ocp_write(tp, 0xcdd2, 0x8c09);
> > + r8168_mac_ocp_write(tp, 0xcdd8, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd4, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdda, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd6, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcddc, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcde8, 0x887a);
> > + r8168_mac_ocp_write(tp, 0xcdea, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdec, 0x8c09);
> > + r8168_mac_ocp_write(tp, 0xcdee, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdf0, 0x8a62);
> > + r8168_mac_ocp_write(tp, 0xcdf2, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdf4, 0x883e);
> > + r8168_mac_ocp_write(tp, 0xcdf6, 0x9003);
> > + r8168_mac_ocp_modify(tp, 0xe032, 0x0000, BIT(14));
> > + break;
> > + case RTL_GIGA_MAC_VER_61 ... RTL_GIGA_MAC_VER_66:
> > + r8168_mac_ocp_write(tp, 0xcdd0, 0x9003);
> > + r8168_mac_ocp_modify(tp, 0xe034, 0x0000, 0xc000);
> > + r8168_mac_ocp_modify(tp, 0xe0a2, 0x0000, BIT(0));
> > + r8168_mac_ocp_write(tp, 0xcdd2, 0x889c);
> > + r8168_mac_ocp_write(tp, 0xcdd8, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd4, 0x8c30);
> > + r8168_mac_ocp_write(tp, 0xcdda, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd6, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcddc, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcde8, 0x883e);
> > + r8168_mac_ocp_write(tp, 0xcdea, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdec, 0x889c);
> > + r8168_mac_ocp_write(tp, 0xcdee, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdf0, 0x8C09);
> > + r8168_mac_ocp_write(tp, 0xcdf2, 0x9003);
> > + r8168_mac_ocp_modify(tp, 0xe032, 0x0000, BIT(14));
> > + break;
> > + case RTL_GIGA_MAC_VER_46 ... RTL_GIGA_MAC_VER_52:
> > + r8168_mac_ocp_modify(tp, 0xe034, 0x0000, 0xc000);
> > + r8168_mac_ocp_modify(tp, 0xe0a2, 0x0000, BIT(0));
> > + r8168_mac_ocp_write(tp, 0xe02c, 0x1880);
> > + r8168_mac_ocp_write(tp, 0xe02e, 0x4880);
> > + r8168_mac_ocp_write(tp, 0xcdd8, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdda, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcddc, 0x9003);
> > + r8168_mac_ocp_write(tp, 0xcdd2, 0x883c);
> > + r8168_mac_ocp_write(tp, 0xcdd4, 0x8c12);
> > + r8168_mac_ocp_write(tp, 0xcdd6, 0x9003);
> > + RTL_W8(tp, 0xb6, RTL_R8(tp, 0xb6) | BIT(0));
> > + break;
> > + default:
> > + return;
> > + }
> > + /* chip can trigger LTR */
> > + r8168_mac_ocp_modify(tp, 0xe032, 0x0003, BIT(0)); }
> > +
> > +static void rtl_disable_ltr(struct rtl8169_private *tp) {
> > + switch (tp->mac_version) {
> > + case RTL_GIGA_MAC_VER_46 ... RTL_GIGA_MAC_VER_80:
> > + r8168_mac_ocp_modify(tp, 0xe032, 0x0003, 0);
> > + break;
> > + default:
> > + break;
> > + }
> > +}
> > +
> > static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp,
> > bool enable) {
> > u8 val8;
> > @@ -2947,6 +3042,7 @@ static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
> > break;
> > }
> >
> > + rtl_enable_ltr(tp);
> > switch (tp->mac_version) {
> > case RTL_GIGA_MAC_VER_46 ... RTL_GIGA_MAC_VER_48:
> > case RTL_GIGA_MAC_VER_61 ... RTL_GIGA_MAC_VER_LAST:
> > @@ -2968,6 +3064,7 @@ static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
> > break;
> > }
> >
> > + rtl_disable_ltr(tp);
> > switch (tp->mac_version) {
> > case RTL_GIGA_MAC_VER_70:
> > case RTL_GIGA_MAC_VER_80:
> > @@ -4811,6 +4908,7 @@ static void rtl8169_down(struct rtl8169_private
> > *tp)
> >
> > rtl8169_cleanup(tp);
> > rtl_disable_exit_l1(tp);
> > + rtl_disable_ltr(tp);
> > rtl_prepare_power_down(tp);
> >
> > if (tp->dash_type != RTL_DASH_NONE && !tp->saved_wolopts)
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