linux-kernel - Re: [PATCH net-next 2/2] net: stmmac: Add callbacks for DWC xpcs Energy Efficient Ethernet

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Message-ID: <20210518100627.GT12395@shell.armlinux.org.uk>
Date:   Tue, 18 May 2021 11:06:27 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     "Sit, Michael Wei Hong" <michael.wei.hong.sit@...el.com>
Cc:     "Jose.Abreu@...opsys.com" <Jose.Abreu@...opsys.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "Voon, Weifeng" <weifeng.voon@...el.com>,
        "Ong, Boon Leong" <boon.leong.ong@...el.com>,
        "Tan, Tee Min" <tee.min.tan@...el.com>,
        "vee.khee.wong@...ux.intel.com" <vee.khee.wong@...ux.intel.com>,
        "Wong, Vee Khee" <vee.khee.wong@...el.com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 2/2] net: stmmac: Add callbacks for DWC xpcs
 Energy Efficient Ethernet

On Mon, May 17, 2021 at 11:37:12AM +0000, Sit, Michael Wei Hong wrote:
> > From: Russell King <linux@...linux.org.uk>
> > 
> > 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@...el.com>
> > 
> > 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.

Does that hardware default configuration match what is returned by
ethtool --show-eee ?
 
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