[PATCH] net: eqos: connect and config PHY from probe stage instead of starting EQOS

[Joakim Zhang]

Hi Ramon,

> -----Original Message-----
> From: Ramon Fried <rfried.dev at gmail.com>
> Sent: 2021年11月16日 13:57
> To: Joakim Zhang <qiangqing.zhang at nxp.com>
> Cc: Joe Hershberger <joe.hershberger at ni.com>; U-Boot Mailing List
> <u-boot at lists.denx.de>; Ye Li <ye.li at nxp.com>; Patrick Delaunay
> <patrick.delaunay at foss.st.com>; Daniil Stas <daniil.stas at posteo.net>;
> Stephen Warren <swarren at nvidia.com>
> Subject: Re: [PATCH] net: eqos: connect and config PHY from probe stage
> instead of starting EQOS
> 
> On Wed, Nov 10, 2021 at 7:42 AM Joakim Zhang <qiangqing.zhang at nxp.com>
> wrote:
> >
> > For EQOS ethernet, it will do phy_connect() and phy_config() when
> > start the ethernet (eqos_srart()), users need wait seconds for PHY
> > auto negotiation to complete when do tftp boot.
> >     phy_config()
> >             -> board_phy_config()
> >                     -> phydev->drv->config() // i.MX8MP/DXL use
> realtek PHY
> >                             -> rtl8211f_config()
> >                                     -> genphy_config_aneg()
> >                                             ->
> genphy_restart_aneg()
> > // restart auto-nego, then need seconds to complete
> >
> > To avoid wasting time, we can move PHY connection and configuration
> > from
> > eqos_start() to eqos_probe(). This patch also moves clock setting from
> > eqos_start() to eqos_probe() as MDIO access need CSR clock, there is
> > no function change.
> >
> > Tested-on: i.MX8MP & i.MX8DXL
> >
> > Before:
> > u-boot=> run netboot
> > Booting from net ...
> > ethernet at 30bf0000 Waiting for PHY auto negotiation to complete.......
> > done BOOTP broadcast 1 DHCP client bound to address 10.193.102.192
> > (313 ms) Using ethernet at 30bf0000 device TFTP from server
> > 10.193.108.176; our IP address is 10.193.102.192; sending through
> > gateway 10.193.102.254
> > After:
> > u-boot=> run netboot
> > Booting from net ...
> > BOOTP broadcast 1
> > DHCP client bound to address 10.193.102.192 (454 ms) Using
> > ethernet at 30bf0000 device TFTP from server 10.193.108.176; our IP
> > address is 10.193.102.192; sending through gateway 10.193.102.254
> >
> How much time do you save exactly, Is it the ~140ms you show here at the
> commit log ?

Exactly not. This time points to DHCP client bound to address, not the time this patch saves.

How can we evaluate the time we save? Please see the log:

Before:
    Booting from net ...
    ethernet at 30bf0000 Waiting for PHY auto negotiation to complete....... done
    BOOTP broadcast 1
After:
    Booting from net ...
    BOOTP broadcast 1	

And you need to check the related code:
drivers/net/dwc_eth_qos.c: phy_startup ->...->
drivers/net/phy/phy.c: genphy_update_link()

https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/net/phy/phy.c#L225

		while (!(mii_reg & BMSR_ANEGCOMPLETE)) {
			/*
			 * Timeout reached ?
			 */
			if (i > (PHY_ANEG_TIMEOUT / 50)) {
				printf(" TIMEOUT !\n");
				phydev->link = 0;
				return -ETIMEDOUT;
			}

			if (ctrlc()) {
				puts("user interrupt!\n");
				phydev->link = 0;
				return -EINTR;
			}

			if ((i++ % 10) == 0)
				printf(".");

			mii_reg = phy_read(phydev, MDIO_DEVAD_NONE, MII_BMSR);
			mdelay(50);	/* 50 ms */
		}

We can see that one "." is about 500ms, so from the log, we save about 500*7=3500ms=3.5s, this also means that PHY needs about 3.5s to complete auto-nego.

I also described this in the commit message, "users need wait seconds for PHY auto negotiation to complete when do tftp boot", may not quite clear, I will improve it.

Best Regards,
Joakim Zhang