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From:   "Sit, Michael Wei Hong" <michael.wei.hong.sit@intel.com>
To:     Russell King <linux@armlinux.org.uk>
CC:     "Jose.Abreu@synopsys.com" <Jose.Abreu@synopsys.com>,
        "andrew@lunn.ch" <andrew@lunn.ch>,
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        "Voon, Weifeng" <weifeng.voon@intel.com>,
        "Ong, Boon Leong" <boon.leong.ong@intel.com>,
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Subject: RE: [PATCH net-next 2/2] net: stmmac: Add callbacks for DWC xpcs
 Energy Efficient Ethernet
Thread-Topic: [PATCH net-next 2/2] net: stmmac: Add callbacks for DWC xpcs
 Energy Efficient Ethernet
Thread-Index: AQHXSwHXH3A7a02UTEaLpjsECGhB/Krnf/sAgAAJ7wA=
Date:   Mon, 17 May 2021 11:37:12 +0000
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References: <20210517094332.24976-1-michael.wei.hong.sit@intel.com>
 <20210517094332.24976-3-michael.wei.hong.sit@intel.com>
 <20210517105424.GP12395@shell.armlinux.org.uk>
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> -----Original Message-----
> From: Russell King <linux@armlinux.org.uk>
> Sent: Monday, 17 May, 2021 6:54 PM
> To: Sit, Michael Wei Hong <michael.wei.hong.sit@intel.com>
> Cc: Jose.Abreu@synopsys.com; andrew@lunn.ch;
> hkallweit1@gmail.com; kuba@kernel.org;
> netdev@vger.kernel.org; peppe.cavallaro@st.com;
> alexandre.torgue@foss.st.com; davem@davemloft.net;
> mcoquelin.stm32@gmail.com; Voon, Weifeng
> <weifeng.voon@intel.com>; Ong, Boon Leong
> <boon.leong.ong@intel.com>; Tan, Tee Min
> <tee.min.tan@intel.com>; vee.khee.wong@linux.intel.com;
> Wong, Vee Khee <vee.khee.wong@intel.com>; linux-stm32@st-
> md-mailman.stormreply.com; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH net-next 2/2] net: stmmac: Add callbacks for
> DWC xpcs Energy Efficient Ethernet
>=20
> On Mon, May 17, 2021 at 05:43:32PM +0800, Michael Sit Wei Hong
> wrote:
> > Link xpcs callback functions for MAC to configure the xpcs EEE
> feature.
> >
> > The clk_eee frequency is used to calculate the
> MULT_FACT_100NS. This
> > is to adjust the clock tic closer to 100ns.
> >
> > Signed-off-by: Michael Sit Wei Hong
> <michael.wei.hong.sit@intel.com>
>=20
> What is the initial state of the EEE configuration before the first
> call to stmmac_ethtool_op_set_eee()? Does it reflect the default
> EEE settings?

The register values before the first call are the default reset values in
the registers. The reset values assumes the clk_eee_i time period is 10ns,
Hence, the reset value is set to 9.
According to the register description,
This value should be programmed such that the
clk_eee_i_time_period * (MULT_FACT_100NS + 1) should be
within 80 ns to 120 ns.

Since we are using a fixed 19.2MHz clk_eee, which is 52ns,
we are setting the value to 1.
>=20
> --
> RMK's Patch system:
> https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at
> last!