netdev - RE: [PATCH net-next 4/6] r8152: support new chips

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Date:   Tue, 20 Apr 2021 07:00:39 +0000
From:   Hayes Wang <hayeswang@...ltek.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        nic_swsd <nic_swsd@...ltek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: [PATCH net-next 4/6] r8152: support new chips

Jakub Kicinski <kuba@...nel.org>
> Sent: Saturday, April 17, 2021 5:50 AM
> > +	switch (tp->version) {
> > +	case RTL_VER_10:
> > +		data = ocp_reg_read(tp, 0xad40);
> > +		data &= ~0x3ff;
> > +		data |= BIT(7) | BIT(2);
> > +		ocp_reg_write(tp, 0xad40, data);
> > +
> > +		data = ocp_reg_read(tp, 0xad4e);
> > +		data |= BIT(4);
> > +		ocp_reg_write(tp, 0xad4e, data);
> > +		data = ocp_reg_read(tp, 0xad16);
> > +		data &= ~0x3ff;
> > +		data |= 0x6;
> > +		ocp_reg_write(tp, 0xad16, data);
> > +		data = ocp_reg_read(tp, 0xad32);
> > +		data &= ~0x3f;
> > +		data |= 6;
> > +		ocp_reg_write(tp, 0xad32, data);
> > +		data = ocp_reg_read(tp, 0xac08);
> > +		data &= ~(BIT(12) | BIT(8));
> > +		ocp_reg_write(tp, 0xac08, data);
> > +		data = ocp_reg_read(tp, 0xac8a);
> > +		data |= BIT(12) | BIT(13) | BIT(14);
> > +		data &= ~BIT(15);
> > +		ocp_reg_write(tp, 0xac8a, data);
> > +		data = ocp_reg_read(tp, 0xad18);
> > +		data |= BIT(10);
> > +		ocp_reg_write(tp, 0xad18, data);
> > +		data = ocp_reg_read(tp, 0xad1a);
> > +		data |= 0x3ff;
> > +		ocp_reg_write(tp, 0xad1a, data);
> > +		data = ocp_reg_read(tp, 0xad1c);
> > +		data |= 0x3ff;
> > +		ocp_reg_write(tp, 0xad1c, data);
> > +
> > +		data = sram_read(tp, 0x80ea);
> > +		data &= ~0xff00;
> > +		data |= 0xc400;
> > +		sram_write(tp, 0x80ea, data);
> > +		data = sram_read(tp, 0x80eb);
> > +		data &= ~0x0700;
> > +		data |= 0x0300;
> > +		sram_write(tp, 0x80eb, data);
> > +		data = sram_read(tp, 0x80f8);
> > +		data &= ~0xff00;
> > +		data |= 0x1c00;
> > +		sram_write(tp, 0x80f8, data);
> > +		data = sram_read(tp, 0x80f1);
> > +		data &= ~0xff00;
> > +		data |= 0x3000;
> > +		sram_write(tp, 0x80f1, data);

These are the parameters of PHY.
Some are used for speed down about power saving.
And some are used for performance.

> > +	switch (tp->version) {
> > +	case RTL_VER_12:
> > +		ocp_reg_write(tp, 0xbf86, 0x9000);
> > +		data = ocp_reg_read(tp, 0xc402);
> > +		data |= BIT(10);
> > +		ocp_reg_write(tp, 0xc402, data);
> > +		data &= ~BIT(10);
> > +		ocp_reg_write(tp, 0xc402, data);
> > +		ocp_reg_write(tp, 0xbd86, 0x1010);
> > +		ocp_reg_write(tp, 0xbd88, 0x1010);
> > +		data = ocp_reg_read(tp, 0xbd4e);
> > +		data &= ~(BIT(10) | BIT(11));
> > +		data |= BIT(11);
> > +		ocp_reg_write(tp, 0xbd4e, data);
> > +		data = ocp_reg_read(tp, 0xbf46);
> > +		data &= ~0xf00;
> > +		data |= 0x700;
> > +		ocp_reg_write(tp, 0xbf46, data);

These are used to adjust the clock of GPHY.
It influences the linking.

> > +	data = r8153_phy_status(tp, 0);
> > +	switch (data) {
> > +	case PHY_STAT_EXT_INIT:
> > +		rtl8152_apply_firmware(tp, true);
> > +
> > +		data = ocp_reg_read(tp, 0xa466);
> > +		data &= ~BIT(0);
> > +		ocp_reg_write(tp, 0xa466, data);

These let the PHY exit PHY_STAT_EXT_INIT state.

> What are all these magic constants? :(

I think it is difficult for me to make all magic values meaningful.
The PHY setting is very complex. Only PHY engineers know
what are the settings mean.

> > @@ -6878,7 +8942,11 @@ static int rtl8152_probe(struct usb_interface
> *intf,
> >  	set_ethernet_addr(tp);
> >
> >  	usb_set_intfdata(intf, tp);
> > -	netif_napi_add(netdev, &tp->napi, r8152_poll, RTL8152_NAPI_WEIGHT);
> > +
> > +	if (tp->support_2500full)
> > +		netif_napi_add(netdev, &tp->napi, r8152_poll, 256);
> 
> why 256? We have 100G+ drivers all using 64 what's special here?
> 
> > +	else
> > +		netif_napi_add(netdev, &tp->napi, r8152_poll, 64);

We test 2.5G Ethernet on some embedded platform.
And we find 64 is not large enough, and the performance
couldn't reach 2.5 G bits/s.

Best Regards,
Hayes