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Subject: Re: [PATCH 1/3] net: ethernet: add support for PCS and 2.5G speed
To:     Parshuram Raju Thombare <pthombar@cadence.com>,
        "nicolas.ferre@microchip.com" <nicolas.ferre@microchip.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "andrew@lunn.ch" <andrew@lunn.ch>,
        "hkallweit1@gmail.com" <hkallweit1@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Rafal Ciepiela <rafalc@cadence.com>,
        Piotr Sroka <piotrs@cadence.com>, Jan Kotas <jank@cadence.com>
References: <20190222201225.GA15633@lvlogina.cadence.com>
 <673edcd1-9ea5-9efe-1f66-3f8ea8d3f092@gmail.com>
 <CO2PR07MB2469FCDFEE81BE4D3ECE9C92C17A0@CO2PR07MB2469.namprd07.prod.outlook.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
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Message-ID: <65c93555-f0d2-1139-a4fd-5c6a80acd9bf@gmail.com>
Date:   Mon, 25 Feb 2019 09:21:23 -0800
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On 2/25/19 1:11 AM, Parshuram Raju Thombare wrote:
>> Le 2/22/19 à 12:12 PM, Parshuram Thombare a écrit :
>>> This patch add support for PCS (for SGMII interface) and 2.5Gbps MAC
>>> in Cadence ethernet controller driver.
>>
>> At a high level you don't seem to be making use of PHYLINK so which 2.5Gbps
>> interfaces do you actually support?
>>
> 
> New ethernet controller have MAC which support 2.5G speed. 
> Also there is addition of PCS and SGMII interface.

I should have asked this more clearly: have you tested with SFP modules
for instance? If you want to be able to reliably support 2500baseT
and/or 2500baseX with hot plugging of such modules, you need to
implement PHYLINK for that network driver, there is no other way around.

> 
>>>
>>> Signed-off-by: Parshuram Thombare <pthombar@cadence.com>
>>> ---
>>
>> [snip]
>>
>>> @@ -361,26 +361,50 @@ static int macb_mdio_write(struct mii_bus *bus, int
>> mii_id, int regnum,
>>>   * macb_set_tx_clk() - Set a clock to a new frequency
>>>   * @clk		Pointer to the clock to change
>>>   * @rate	New frequency in Hz
>>> + * @interafce	Phy interface
>>
>> Typo: @interface and this is an unrelated change.
>>
>>>   * @dev		Pointer to the struct net_device
>>>   */
>>> -static void macb_set_tx_clk(struct clk *clk, int speed, struct
>>> net_device *dev)
>>> +static void macb_set_tx_clk(struct clk *clk, int speed,
>>> +			    phy_interface_t interface, struct net_device *dev)
>>>  {
>>>  	long ferr, rate, rate_rounded;
>>>
>>>  	if (!clk)
>>>  		return;
>>>
>>> -	switch (speed) {
>>> -	case SPEED_10:
>>> +	if (interface == PHY_INTERFACE_MODE_GMII ||
>>> +	    interface == PHY_INTERFACE_MODE_MII) {
>>> +		switch (speed) {
>>> +		case SPEED_10:>  		rate = 2500000;
>>
>> You need to add one tab to align rate and break.
> 
> Do you mean a tab each for rate and break lines ?
> All switch statements are aligned at a tab.  I am not sure how does case and rate got on same line.

It should look like this:

switch (cond) {
case cond1:
	do_something();
	break;

etc.

> 
>>
>>>  		break;
>>> -	case SPEED_100:
>>> +		case SPEED_100:
>>>  		rate = 25000000;
>>>  		break;
>>> -	case SPEED_1000:
>>> +		case SPEED_1000:
>>>  		rate = 125000000;
>>>  		break;
>>> -	default:
>>> +		default:
>>> +		return;
>>> +		}
>>> +	} else if (interface == PHY_INTERFACE_MODE_SGMII) {
>>> +		switch (speed) {
>>> +		case SPEED_10:
>>> +		rate = 1250000;
>>> +		break;
>>> +		case SPEED_100:
>>> +		rate = 12500000;
>>> +		break;
>>> +		case SPEED_1000:
>>> +		rate = 125000000;
>>> +		break;
>>> +		case SPEED_2500:
>>> +		rate = 312500000;
>>> +		break;
>>> +		default:
>>> +		return;
>>
>> The indentation is broken here and you can greatly simplify this with a simple
>> function that returns speed * 1250 and does an initial check for unsupported
>> speeds.
>>
> 
> I ran checkpatch.pl and all indentation issues were cleared. But I think having function
> is better option, I will make that change.
> 
>>> +		}
>>> +	} else {
>>>  		return;
>>>  	}
>>>
>>> @@ -410,30 +434,49 @@ static void macb_handle_link_change(struct
>>> net_device *dev)
>>>
>>>  	spin_lock_irqsave(&bp->lock, flags);
>>>
>>> -	if (phydev->link) {
>>> -		if ((bp->speed != phydev->speed) ||
>>> -		    (bp->duplex != phydev->duplex)) {
>>> -			u32 reg;
>>> -
>>> -			reg = macb_readl(bp, NCFGR);
>>> -			reg &= ~(MACB_BIT(SPD) | MACB_BIT(FD));
>>> -			if (macb_is_gem(bp))
>>> -				reg &= ~GEM_BIT(GBE);
>>> +	if (phydev->link && (bp->speed != phydev->speed ||
>>> +			     bp->duplex != phydev->duplex)) {
>>> +		u32 reg;
>>>
>>> -			if (phydev->duplex)
>>> -				reg |= MACB_BIT(FD);
>>> +		reg = macb_readl(bp, NCFGR);
>>> +		reg &= ~(MACB_BIT(SPD) | MACB_BIT(FD));
>>> +		if (macb_is_gem(bp))
>>> +			reg &= ~GEM_BIT(GBE);
>>> +		if (phydev->duplex)
>>> +			reg |= MACB_BIT(FD);
>>> +		macb_or_gem_writel(bp, NCFGR, reg);
>>> +
>>> +		if (bp->phy_interface == PHY_INTERFACE_MODE_SGMII &&
>>> +		    (phydev->speed == SPEED_1000 ||
>>> +		     phydev->speed == SPEED_2500)) {
>>> +			if (bp->caps & MACB_CAPS_TWO_PT_FIVE_GIG_SPEED) {
>>> +				reg = gem_readl(bp, NCR) &
>>> +					~GEM_BIT(TWO_PT_FIVE_GIG);
>>> +				gem_writel(bp, NCR, reg);
>>> +			}
>>
>> If you are making correct use of the capabilities then there is no point in re-
>> checking them here. If you allowed the MAC to advertise 2.5Gbps then it is de-
>> facto SGMII capable.
> 
> PHY_INTERFACE_MODE_SGMII is selected only on the basis of presence of PCS.
> This additional check is to make sure PHY also support 1G/2.5G.

My point is that you should never get to that function with
bp->phy_interface == PHY_INTERFACE_MODE_SGMII if you have done necessary
verifications at the time you connect to the PHY. If you let
PHY_INTERFACE_MODE_SGMII go through on a Cadence IP version that does
not have the MACB_CAPS_TWO_PT_FIVE_GIG_SPEED capability bit set, then
this is broken.

> 
>>> +			gem_writel(bp, NCFGR, GEM_BIT(GBE) |
>>> +					gem_readl(bp, NCFGR));
>>> +			if (bp->caps & MACB_CAPS_TWO_PT_FIVE_GIG_SPEED
>> &&
>>> +			    phydev->speed == SPEED_2500)
>>> +				gem_writel(bp, NCR, gem_readl(bp, NCR) |
>>> +						GEM_BIT(TWO_PT_FIVE_GIG));
>>> +		} else if (phydev->speed == SPEED_1000) {
>>> +			gem_writel(bp, NCFGR, GEM_BIT(GBE) |
>>> +					gem_readl(bp, NCFGR));
>>> +		} else {
>>> +			if (bp->phy_interface == PHY_INTERFACE_MODE_SGMII)
>> {
>>> +				reg = gem_readl(bp, NCFGR);
>>> +				reg &= ~(GEM_BIT(SGMIIEN) |
>> GEM_BIT(PCSSEL));
>>> +				gem_writel(bp, NCFGR, reg);
>>> +			}
>>>  			if (phydev->speed == SPEED_100)
>>> -				reg |= MACB_BIT(SPD);
>>> -			if (phydev->speed == SPEED_1000 &&
>>> -			    bp->caps & MACB_CAPS_GIGABIT_MODE_AVAILABLE)
>>> -				reg |= GEM_BIT(GBE);
>>> -
>>> -			macb_or_gem_writel(bp, NCFGR, reg);
>>> -
>>> -			bp->speed = phydev->speed;
>>> -			bp->duplex = phydev->duplex;
>>> -			status_change = 1;
>>> +				macb_writel(bp, NCFGR, MACB_BIT(SPD) |
>>> +					macb_readl(bp, NCFGR));
>>>  		}
>>
>> There is a lot of repetition while setting the GBE bit which always set based on
>> speed == 1000 irrespective of the mode, so take that part out of the if () else if ()
>> else () clauses.
>>
> 
> Ok, I will change it.
> 
>>> +
>>> +		bp->speed = phydev->speed;
>>> +		bp->duplex = phydev->duplex;
>>> +		status_change = 1;
>>>  	}
>>>
>>>  	if (phydev->link != bp->link) {
>>> @@ -453,7 +496,8 @@ static void macb_handle_link_change(struct net_device
>> *dev)
>>>  			/* Update the TX clock rate if and only if the link is
>>>  			 * up and there has been a link change.
>>>  			 */
>>> -			macb_set_tx_clk(bp->tx_clk, phydev->speed, dev);
>>> +			macb_set_tx_clk(bp->tx_clk, phydev->speed,
>>> +					bp->phy_interface, dev);
>>>
>>>  			netif_carrier_on(dev);
>>>  			netdev_info(dev, "link up (%d/%s)\n", @@ -543,10
>> +587,16 @@ static
>>> int macb_mii_probe(struct net_device *dev)
>>>  	}
>>>
>>>  	/* mask with MAC supported features */
>>> -	if (macb_is_gem(bp) && bp->caps &
>> MACB_CAPS_GIGABIT_MODE_AVAILABLE)
>>> -		phy_set_max_speed(phydev, SPEED_1000);
>>> -	else
>>> -		phy_set_max_speed(phydev, SPEED_100);
>>> +	if (macb_is_gem(bp)) {
>>
>> You have changed the previous logic that also checked for
>> MACB_CAPS_GIGABIT_MODE_AVAILABLE, why?
> 
> My understanding is all GEM (ID >= 0x2) support GIGABIT mode. 
> Was there any other reason for this check ?

Well, if anyone would know, it would be you, I don't work for Cadence
nor have access to the internal IP documentation.

> 
>>> +		linkmode_copy(phydev->supported, PHY_GBIT_FEATURES);
>>> +		if (bp->caps & MACB_CAPS_TWO_PT_FIVE_GIG_SPEED)
>>> +
>> 	linkmode_set_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT,
>>> +					 phydev->supported);
>>> +	} else {
>>> +		linkmode_copy(phydev->supported, PHY_BASIC_FEATURES);
>>> +	}
>>> +
>>> +	linkmode_copy(phydev->advertising, phydev->supported);
>>>
>>>  	if (bp->caps & MACB_CAPS_NO_GIGABIT_HALF)
>>>  		phy_remove_link_mode(phydev,
>>> @@ -2217,8 +2267,6 @@ static void macb_init_hw(struct macb *bp)
>>>  	macb_set_hwaddr(bp);
>>>
>>>  	config = macb_mdc_clk_div(bp);
>>> -	if (bp->phy_interface == PHY_INTERFACE_MODE_SGMII)
>>> -		config |= GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL);
>>>  	config |= MACB_BF(RBOF, NET_IP_ALIGN);	/* Make eth data
>> aligned */
>>>  	config |= MACB_BIT(PAE);		/* PAuse Enable */
>>>  	config |= MACB_BIT(DRFCS);		/* Discard Rx FCS */
>>> @@ -3255,6 +3303,23 @@ static void macb_configure_caps(struct macb *bp,
>>>  		dcfg = gem_readl(bp, DCFG1);
>>>  		if (GEM_BFEXT(IRQCOR, dcfg) == 0)
>>>  			bp->caps |= MACB_CAPS_ISR_CLEAR_ON_WRITE;
>>> +		if (GEM_BFEXT(NO_PCS, dcfg) == 0)
>>> +			bp->caps |= MACB_CAPS_PCS;
>>> +		switch (MACB_BFEXT(IDNUM, macb_readl(bp, MID))) {
>>> +		case MACB_GEM7016_IDNUM:
>>> +		case MACB_GEM7017_IDNUM:
>>> +		case MACB_GEM7017A_IDNUM:
>>> +		case MACB_GEM7020_IDNUM:
>>> +		case MACB_GEM7021_IDNUM:
>>> +		case MACB_GEM7021A_IDNUM:
>>> +		case MACB_GEM7022_IDNUM:
>>> +		if (bp->caps & MACB_CAPS_PCS)
>>> +			bp->caps |= MACB_CAPS_TWO_PT_FIVE_GIG_SPEED;
>>> +		break;
>>> +
>>> +		default:
>>> +		break;
>>> +		}
>>>  		dcfg = gem_readl(bp, DCFG2);
>>>  		if ((dcfg & (GEM_BIT(RX_PKT_BUFF) | GEM_BIT(TX_PKT_BUFF)))
>> == 0)
>>>  			bp->caps |= MACB_CAPS_FIFO_MODE;
>>> @@ -4110,7 +4175,28 @@ static int macb_probe(struct platform_device
>> *pdev)
>>>  		else
>>>  			bp->phy_interface = PHY_INTERFACE_MODE_MII;
>>>  	} else {
>>> +		switch (err) {
>>> +		case PHY_INTERFACE_MODE_SGMII:
>>> +		if (bp->caps & MACB_CAPS_PCS) {
>>> +			bp->phy_interface = PHY_INTERFACE_MODE_SGMII;
>>> +			break;
>>> +		}
>>
>> If SGMII was selected on a version of the IP that does not support it, then falling
>> back to GMII or MII does not sound correct, this is a hard error that must be
>> handled as such.
>> --
>> Florian
> 
> My intention was to continue (instead of failing) with whatever functionality is available.
> Can we have some error message and continue with what is available ?

This is probably not going to help anyone, imagine you incorrectly
specified a 'phy-mode' property in the Device Tree and you have to dig
into the driver in the function that sets the clock rate to find out
what you just defaulted to 1Gbits/GMII for instance. This is not user
friendly at all and will increase the support burden on your end as
well, if SGMII is specified and the IP does not support it, detect it
and return an error, how that propagates, either as a probe failure or
the inability to open the network device, your call.
-- 
Florian