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Date:   Fri, 26 Apr 2019 23:26:24 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: realtek: Add rtl8211e rx/tx delays config

On Fri, Apr 26, 2019 at 07:17:44PM +0200, Heiner Kallweit wrote:
> On 26.04.2019 11:30, Serge Semin wrote:
> > There are two chip pins named TXDLY and RXDLY which actually addes
> > the 2ns delays to TXC and RXC for TXD/RXD latching. Alas it is only
> > documented info regarding the RGMII timing control configurations
> > the PHY provides. It turnes out the same settings can be setup
> > via MDIO registers hidden in the extension pages layout.
> > Particularly the extension page 0xa4 provides a register 0x1c,
> > which bits 1 and 2 control the described delays. They are used
> > to implemet the "rgmii-{id,rxid,txid}" phy-mode.
> > 
> There are few typos in the commit message.
> 

I'll fix them in v2. Thank you.

> > The hidden RGMII configs register utilization was found in the
> > rtl8211e U-boot driver:
> > https://elixir.bootlin.com/u-boot/v2019.01/source/drivers/net/phy/realtek.c#L99
> > 
> > There is also a freebsd discussion regarding this register:
> > https://reviews.freebsd.org/D13591
> > 
> > It confirms that the register bits field must control the so called
> > configuration pins described in the table 12-13 of the official PHY
> > datasheet:
> > 8:6 = PHY Address
> > 5:4 = Auto-Negotiation
> > 3 = Interface Mode Select
> > 2 = RX Delay
> > 1 = TX Delay
> > 0 = SELRGV
> > 
> > Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> > ---
> >  drivers/net/phy/realtek.c | 44 +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> > 
> > diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
> > index 10df52ccddfe..8776b94d91ed 100644
> > --- a/drivers/net/phy/realtek.c
> > +++ b/drivers/net/phy/realtek.c
> > @@ -23,11 +23,14 @@
> >  
> >  #define RTL821x_INSR				0x13
> >  
> > +#define RTL821x_EXT_PAGE_SELECT			0x1e
> >  #define RTL821x_PAGE_SELECT			0x1f
> >  
> >  #define RTL8211F_INSR				0x1d
> >  
> >  #define RTL8211F_TX_DELAY			BIT(8)
> > +#define RTL8211E_TX_DELAY			BIT(1)
> > +#define RTL8211E_RX_DELAY			BIT(2)
> >  
> >  #define RTL8201F_ISR				0x1e
> >  #define RTL8201F_IER				0x13
> > @@ -174,6 +177,46 @@ static int rtl8211f_config_init(struct phy_device *phydev)
> >  	return phy_modify_paged(phydev, 0xd08, 0x11, RTL8211F_TX_DELAY, val);
> >  }
> >  
> > +static int rtl8211e_config_init(struct phy_device *phydev)
> > +{
> > +	int ret, oldpage;
> > +	u16 val = 0;
> > +
> > +	ret = genphy_config_init(phydev);
> 
> There's no need to call genphy_config_init().
> 

Right. I'll fix it in v2. It's working even with calling the function though.

> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* enable TX/RX delay for rgmii-* modes, otherwise disable it */
> > +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
> > +		val = RTL8211E_TX_DELAY | RTL8211E_RX_DELAY;
> > +	else if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID)
> > +		val = RTL8211E_TX_DELAY;
> > +	else if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID)
> > +		val = RTL8211E_RX_DELAY;
> > +
> > +	/* According to a sample driver there is a 0x1c config register on
> > +	 * a 0xa4 extension page (0x7) layout. It can be used to disable/enable
> > +	 * the RX/TX delays otherwise controlled by hardware strobes. It can
> > +	 * also be used to customize the whole configuration register:
> > +	 * 8:6 = PHY Address, 5:4 = Auto-Negotiation, 3 = Interface Mode Select,
> > +	 * 2 = RX Delay, 1 = TX Delay, 0 = SELRGV (see original PHY datasheet
> > +	 * for details).
> > +	 */
> > +	oldpage = phy_select_page(phydev, 0x7);
> > +	if (oldpage < 0)
> > +		goto err_restore_page;
> > +
> > +	ret = phy_write(phydev, RTL821x_EXT_PAGE_SELECT, 0xa4);
> > +	if (!ret)
> 
> I think this should be: if (ret)
> 

My goodness. What a shame on me to miss this! I ported this function from an older
kernel, and apparently didn't do this accurate enough. Sorry for this awful
bug. I'll fix it in the next patch revision.

-Sergey

> > +		goto err_restore_page;
> > +
> > +	ret = phy_modify(phydev, 0x1c, RTL8211E_TX_DELAY | RTL8211E_RX_DELAY,
> > +			 val);
> > +
> > +err_restore_page:
> > +	return phy_restore_page(phydev, oldpage, ret);
> > +}
> > +
> >  static int rtl8211b_suspend(struct phy_device *phydev)
> >  {
> >  	phy_write(phydev, MII_MMD_DATA, BIT(9));
> > @@ -257,6 +300,7 @@ static struct phy_driver realtek_drvs[] = {
> >  		PHY_ID_MATCH_EXACT(0x001cc915),
> >  		.name		= "RTL8211E Gigabit Ethernet",
> >  		.features	= PHY_GBIT_FEATURES,
> > +		.config_init	= &rtl8211e_config_init,
> >  		.ack_interrupt	= &rtl821x_ack_interrupt,
> >  		.config_intr	= &rtl8211e_config_intr,
> >  		.suspend	= genphy_suspend,
> > 
> 

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