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Subject: Re: [PATCH v2] net: phy: realtek: read actual speed on rtl8211f to
 detect downshift
From:   Antonio Borneo <antonio.borneo@st.com>
To:     Heiner Kallweit <hkallweit1@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, <netdev@vger.kernel.org>,
        Yonglong Liu <liuyonglong@huawei.com>,
        Willy Liu <willy.liu@realtek.com>
CC:     <linuxarm@huawei.com>, Salil Mehta <salil.mehta@huawei.com>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-kernel@vger.kernel.org>
Date:   Tue, 24 Nov 2020 23:33:42 +0100
In-Reply-To: <7d8bf728-7d73-fa8c-d63d-49e9e6c872fd@gmail.com>
References: <20201124143848.874894-1-antonio.borneo@st.com>
         <20201124215932.885306-1-antonio.borneo@st.com>
         <7d8bf728-7d73-fa8c-d63d-49e9e6c872fd@gmail.com>
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On Tue, 2020-11-24 at 23:22 +0100, Heiner Kallweit wrote:
> Am 24.11.2020 um 22:59 schrieb Antonio Borneo:
> > The rtl8211f supports downshift and before commit 5502b218e001
> > ("net: phy: use phy_resolve_aneg_linkmode in genphy_read_status")
> > the read-back of register MII_CTRL1000 was used to detect the
> > negotiated link speed.
> > The code added in commit d445dff2df60 ("net: phy: realtek: read
> > actual speed to detect downshift") is working fine also for this
> > phy and it's trivial re-using it to restore the downshift
> > detection on rtl8211f.
> > 
> > Add the phy specific read_status() pointing to the existing
> > function rtlgen_read_status().
> > 
> > Signed-off-by: Antonio Borneo <antonio.borneo@st.com>
> > Link: https://lore.kernel.org/r/478f871a-583d-01f1-9cc5-2eea56d8c2a7@huawei.com
> > ---
> > To: Andrew Lunn <andrew@lunn.ch>
> > To: Heiner Kallweit <hkallweit1@gmail.com>
> > To: Russell King <linux@armlinux.org.uk>
> > To: "David S. Miller" <davem@davemloft.net>
> > To: Jakub Kicinski <kuba@kernel.org>
> > To: netdev@vger.kernel.org
> > To: Yonglong Liu <liuyonglong@huawei.com>
> > To: Willy Liu <willy.liu@realtek.com>
> > Cc: linuxarm@huawei.com
> > Cc: Salil Mehta <salil.mehta@huawei.com>
> > Cc: linux-stm32@st-md-mailman.stormreply.com
> > Cc: linux-kernel@vger.kernel.org
> > In-Reply-To: <20201124143848.874894-1-antonio.borneo@st.com>
> > 
> > V1 => V2
> > 	move from a generic implementation affecting every phy
> > 	to a rtl8211f specific implementation
> > ---
> >  drivers/net/phy/realtek.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
> > index 575580d3ffe0..8ff8a4edc173 100644
> > --- a/drivers/net/phy/realtek.c
> > +++ b/drivers/net/phy/realtek.c
> > @@ -621,6 +621,7 @@ static struct phy_driver realtek_drvs[] = {
> >  		PHY_ID_MATCH_EXACT(0x001cc916),
> >  		.name		= "RTL8211F Gigabit Ethernet",
> >  		.config_init	= &rtl8211f_config_init,
> > +		.read_status	= rtlgen_read_status,
> >  		.ack_interrupt	= &rtl8211f_ack_interrupt,
> >  		.config_intr	= &rtl8211f_config_intr,
> >  		.suspend	= genphy_suspend,
> > 
> > base-commit: 9bd2702d292cb7b565b09e949d30288ab7a26d51
> > 
> 
> Pefect would be to make this a fix for 5502b218e001,
> but rtlgen_read_status() was added one year after this change.
> Marking the change that added rtlgen_read_status() as "Fixes"
> would be technically ok, but as it's not actually broken not
> everybody may be happy with this.
> Having said that I'd be fine with treating this as an improvement,
> downshift should be a rare case.

Correct! Being the commit that adds rtlgen_read_status() an improvement,
should not be backported, so this patch is not marked anymore as a fix!
Plus, this does not fix 5502b218e001 in the general case, but limited to
one specific phy, making the 'fixes' label less relevant.
Anyway, the commit message reports all the ingredients for a backport.

By the way, I have incorrectly sent this based on netdev, but it's not a
fix anymore! Should I rebase it on netdev-next and resend?

Antonio