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Date:   Fri, 12 Jun 2020 11:42:08 +0100
From:   Russell King - ARM Linux admin <linux@armlinux.org.uk>
To:     Sascha Hauer <s.hauer@pengutronix.de>
Cc:     linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        kernel@pengutronix.de
Subject: Re: [PATCH v2] net: mvneta: Fix Serdes configuration for 2.5Gbps
 modes
Message-ID: <20200612104208.GG1551@shell.armlinux.org.uk>
References: <20200612083847.29942-1-s.hauer@pengutronix.de>
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 <20200612100114.GE1551@shell.armlinux.org.uk>
 <20200612101820.GF1551@shell.armlinux.org.uk>
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On Fri, Jun 12, 2020 at 11:18:20AM +0100, Russell King - ARM Linux admin wrote:
> On Fri, Jun 12, 2020 at 11:01:15AM +0100, Russell King - ARM Linux admin wrote:
> > On Fri, Jun 12, 2020 at 09:47:10AM +0100, Russell King - ARM Linux admin wrote:
> > > On Fri, Jun 12, 2020 at 10:38:47AM +0200, Sascha Hauer wrote:
> > > > The Marvell MVNETA Ethernet controller supports a 2.5Gbps SGMII mode
> > > > called DRSGMII. Depending on the Port MAC Control Register0 PortType
> > > > setting this seems to be either an overclocked SGMII mode or 2500BaseX.
> > > > 
> > > > This patch adds the necessary Serdes Configuration setting for the
> > > > 2.5Gbps modes. There is no phy interface mode define for overclocked
> > > > SGMII, so only 2500BaseX is handled for now.
> > > > 
> > > > As phy_interface_mode_is_8023z() returns true for both
> > > > PHY_INTERFACE_MODE_1000BASEX and PHY_INTERFACE_MODE_2500BASEX we
> > > > explicitly test for 1000BaseX instead of using
> > > > phy_interface_mode_is_8023z() to differentiate the different
> > > > possibilities.
> > > > 
> > > > Fixes: da58a931f248f ("net: mvneta: Add support for 2500Mbps SGMII")
> > > > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > > 
> > > 2500base-X is used today on Armada 388 and Armada 3720 platforms and
> > > works - it is known to interoperate with Marvell PP2.2 hardware, as
> > > well was various SFPs such as the Huawei MA5671A at 2.5Gbps.  The way
> > > it is handled on these platforms is via the COMPHY, requesting that
> > > the serdes is upclocked from 1.25Gbps to 3.125Gbps.
> > > 
> > > This "DRSGMII" mode is not mentioned in the functional specs for either
> > > the Armada 388 or Armada 3720, the value you poke into the register is
> > > not mentioned either.  As I've already requested, some information on
> > > exactly what this "DRSGMII" is would be very useful, it can't be
> > > "double-rate SGMII" because that would give you 2Gbps instead of 1Gbps.
> > > 
> > > So, I suspect this breaks the platforms that are known to work.
> > > 
> > > We need a proper description of what DRSGMII is before we can consider
> > > taking any patches for it.
> > 
> > Okay, having dug through the Armada XP, 370, 388, 3720 specs, I think
> > this is fine after all - but something that will help for the future
> > would be to document that this register does not exist on the 388 and
> > 3720 devices (which brings up the question whether we should be writing
> > it there.)  The field was moved into the comphy on those devices.
> > 
> > So, it looks like if we have a comphy, we should not be writing this
> > register.
> > 
> > What's more, the write to MVNETA_SERDES_CFG should not be in
> > mvneta_port_power_up(); it's likely that XP and 370 will not work
> > properly with phylink.  It needs to be done in a similar location to
> > mvneta_comphy_init(), so that phylink can switch between 1G and 2.5G
> > speeds.
> > 
> > As you have an Armada XP system, you are best placed to test moving
> > that write.
> 
> Here's my suggestion - it won't apply to mainline or net* trees, but
> gives you the idea I'm proposing:
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 9e25d608d856..17db74d61bc2 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -107,9 +107,11 @@
>  #define      MVNETA_TX_IN_PRGRS                  BIT(1)
>  #define      MVNETA_TX_FIFO_EMPTY                BIT(8)
>  #define MVNETA_RX_MIN_FRAME_SIZE                 0x247c
> +/* Only exists on Armada XP and Armada 370 */
>  #define MVNETA_SERDES_CFG			 0x24A0
> -#define      MVNETA_SGMII_SERDES_PROTO		 0x0cc7
>  #define      MVNETA_QSGMII_SERDES_PROTO		 0x0667
> +#define      MVNETA_SGMII_SERDES_PROTO		 0x0cc7
> +#define      MVNETA_HSGMII_SERDES_PROTO		 0x1107
>  #define MVNETA_TYPE_PRIO                         0x24bc
>  #define      MVNETA_FORCE_UNI                    BIT(21)
>  #define MVNETA_TXQ_CMD_1                         0x24e4
> @@ -3457,9 +3459,6 @@ static int mvneta_comphy_init(struct mvneta_port *pp)
>  {
>  	int ret;
>  
> -	if (!pp->comphy)
> -		return 0;
> -
>  	ret = phy_set_mode_ext(pp->comphy, PHY_MODE_ETHERNET,
>  			       pp->phy_interface);
>  	if (ret)
> @@ -3468,11 +3467,47 @@ static int mvneta_comphy_init(struct mvneta_port *pp)
>  	return phy_power_on(pp->comphy);
>  }
>  
> +static int mvneta_config_interface(struct mvneta_port *pp,i
> +				   phy_interface_t interface)
> +{
> +	int ret = 0;
> +
> +	if (pp->comphy) {
> +		if (interface == PHY_INTERFACE_MODE_SGMII ||
> +		    interface == PHY_INTERFACE_MODE_1000BASEX ||
> +		    interface == PHY_INTERFACE_MODE_2500BASEX) {
> +			ret = mvneta_comphy_init(pp);
> +		}
> +	} else {
> +		switch (interface) {
> +		case PHY_INTERFACE_MODE_QSGMII:
> +			mvreg_write(pp, MVNETA_SERDES_CFG,
> +				    MVNETA_QSGMII_SERDES_PROTO);
> +			break;
> +
> +		case PHY_INTERFACE_MODE_SGMII:
> +		case PHY_INTERFACE_MODE_1000BASEX:
> +			mvreg_write(pp, MVNETA_SERDES_CFG,
> +				    MVNETA_SGMII_SERDES_PROTO);
> +			break;
> +
> +		case PHY_INTERFACE_MODE_2500BASEX:
> +			mvreg_write(pp, MVNETA_SERDES_CFG,
> +				    MVNETA_HSGMII_SERDES_PROTO);
> +			break;
> +		}
> +	}
> +
> +	pp->phy_interface = interface;
> +
> +	return ret;
> +}
> +
>  static void mvneta_start_dev(struct mvneta_port *pp)
>  {
>  	int cpu;
>  
> -	WARN_ON(mvneta_comphy_init(pp));
> +	WARN_ON(mvneta_config_interface(pp, pp->phy_interface));
>  
>  	mvgmac_set_max_rx_size(&pp->gmac, pp->pkt_size);
>  	mvneta_txq_max_tx_size_set(pp, pp->pkt_size);
> @@ -3702,14 +3737,9 @@ static int mvneta_pcs_config(struct phylink_config *config,
>  	/* We should never see Asym_Pause set */
>  	WARN_ON(phylink_test(advertising, Asym_Pause));
>  
> -	if (pp->comphy && pp->phy_interface != interface &&
> -	    (interface == PHY_INTERFACE_MODE_SGMII ||
> -	     interface == PHY_INTERFACE_MODE_1000BASEX ||
> -	     interface == PHY_INTERFACE_MODE_2500BASEX)) {
> -		pp->phy_interface = interface;
> -
> +	if (pp->phy_interface != interface) {
>  		WARN_ON(phy_power_off(pp->comphy));
> -		WARN_ON(mvneta_comphy_init(pp));
> +		mvneta_config_interface(pp, interface);
>  	}
>  
>  	if (want_1ms_clock) {
> @@ -4794,12 +4824,10 @@ static int mvneta_port_power_up(struct mvneta_port *pp, int phy_mode)
>  	/* MAC Cause register should be cleared */
>  	mvreg_write(pp, MVNETA_UNIT_INTR_CAUSE, 0);
>  
> -	if (phy_mode == PHY_INTERFACE_MODE_QSGMII)
> -		mvreg_write(pp, MVNETA_SERDES_CFG, MVNETA_QSGMII_SERDES_PROTO);
> -	else if (phy_mode == PHY_INTERFACE_MODE_SGMII ||
> -		 phy_interface_mode_is_8023z(phy_mode))
> -		mvreg_write(pp, MVNETA_SERDES_CFG, MVNETA_SGMII_SERDES_PROTO);
> -	else if (!phy_interface_mode_is_rgmii(phy_mode))
> +	if (phy_mode != PHY_INTERFACE_MODE_QSGMII &&
> +	    phy_mode != PHY_INTERFACE_MODE_SGMII &&
> +	    !phy_interface_mode_is_8023z(phy_mode) &&
> +	    !phy_interface_mode_is_rgmii(phy_mode))
>  		return -EINVAL;
>  
>  	return 0;

With the obvious mistakes fixed (extraneous 'i' and lack of default
case), it seems to still work on Armada 388 Clearfog Pro with 2.5G
modules.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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