Subject: Re: [PATCH net] net: marvell: mvpp2: Fix wrong SerDes reconfiguration order

From: "Russell King (Oracle)" <[email-masked]>
Date: Mon, 8 Nov 2021 21:53:50 +0000

On Mon, Nov 08, 2021 at 10:49:18PM +0100, Marek Behún wrote:
> Commit bfe301ebbc94 ("net: mvpp2: convert to use
> mac_prepare()/mac_finish()") introduced a bug wherein it leaves the MAC
> RESET register asserted after mac_finish(), due to wrong order of
> function calls.
> 
> Before it was:
>   .mac_config()
>     mvpp22_mode_reconfigure()
>       assert reset
>     mvpp2_xlg_config()
>       deassert reset
> 
> Now it is:
>   .mac_prepare()
>   .mac_config()
>     mvpp2_xlg_config()
>       deassert reset
>   .mac_finish()
>     mvpp2_xlg_config()
>       assert reset
> 
> Obviously this is wrong.
> 
> This bug is triggered when phylink tries to change the PHY interface
> mode from a GMAC mode (sgmii, 1000base-x, 2500base-x) to XLG mode
> (10gbase-r, xaui). The XLG mode does not work since reset is left
> asserted. Only after
>   ifconfig down && ifconfig up
> is called will the XLG mode work.
> 
> Move the call to mvpp22_mode_reconfigure() to .mac_prepare()
> implementation. Since some of the subsequent functions need to know
> whether the interface is being changed, we unfortunately also need to
> pass around the new interface mode before setting port->phy_interface.
> 
> Fixes: bfe301ebbc94 ("net: mvpp2: convert to use mac_prepare()/mac_finish()")
> Signed-off-by: Marek Behún <[email-masked]>
> Signed-off-by: Russell King (Oracle) <[email-masked]>

Thanks Marek.

For those who may say something about the sign-offs, we were both
working on the problem, and both eventually came up with the same
patch while talking about it on IRC, so this is kind of co-creation
- and hence the two sign-offs.

> ---
>  .../net/ethernet/marvell/mvpp2/mvpp2_main.c   | 38 ++++++++++---------
>  1 file changed, 20 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 587def69a6f7..2b18d89d9756 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -1605,7 +1605,7 @@ static void mvpp22_gop_fca_set_periodic_timer(struct mvpp2_port *port)
>  	mvpp22_gop_fca_enable_periodic(port, true);
>  }
>  
> -static int mvpp22_gop_init(struct mvpp2_port *port)
> +static int mvpp22_gop_init(struct mvpp2_port *port, phy_interface_t interface)
>  {
>  	struct mvpp2 *priv = port->priv;
>  	u32 val;
> @@ -1613,7 +1613,7 @@ static int mvpp22_gop_init(struct mvpp2_port *port)
>  	if (!priv->sysctrl_base)
>  		return 0;
>  
> -	switch (port->phy_interface) {
> +	switch (interface) {
>  	case PHY_INTERFACE_MODE_RGMII:
>  	case PHY_INTERFACE_MODE_RGMII_ID:
>  	case PHY_INTERFACE_MODE_RGMII_RXID:
> @@ -1743,15 +1743,15 @@ static void mvpp22_gop_setup_irq(struct mvpp2_port *port)
>   * lanes by the physical layer. This is why configurations like
>   * "PPv2 (2500BaseX) - COMPHY (2500SGMII)" are valid.
>   */
> -static int mvpp22_comphy_init(struct mvpp2_port *port)
> +static int mvpp22_comphy_init(struct mvpp2_port *port,
> +			      phy_interface_t interface)
>  {
>  	int ret;
>  
>  	if (!port->comphy)
>  		return 0;
>  
> -	ret = phy_set_mode_ext(port->comphy, PHY_MODE_ETHERNET,
> -			       port->phy_interface);
> +	ret = phy_set_mode_ext(port->comphy, PHY_MODE_ETHERNET, interface);
>  	if (ret)
>  		return ret;
>  
> @@ -2172,7 +2172,8 @@ static void mvpp22_pcs_reset_assert(struct mvpp2_port *port)
>  	writel(val & ~MVPP22_XPCS_CFG0_RESET_DIS, xpcs + MVPP22_XPCS_CFG0);
>  }
>  
> -static void mvpp22_pcs_reset_deassert(struct mvpp2_port *port)
> +static void mvpp22_pcs_reset_deassert(struct mvpp2_port *port,
> +				      phy_interface_t interface)
>  {
>  	struct mvpp2 *priv = port->priv;
>  	void __iomem *mpcs, *xpcs;
> @@ -2184,7 +2185,7 @@ static void mvpp22_pcs_reset_deassert(struct mvpp2_port *port)
>  	mpcs = priv->iface_base + MVPP22_MPCS_BASE(port->gop_id);
>  	xpcs = priv->iface_base + MVPP22_XPCS_BASE(port->gop_id);
>  
> -	switch (port->phy_interface) {
> +	switch (interface) {
>  	case PHY_INTERFACE_MODE_10GBASER:
>  		val = readl(mpcs + MVPP22_MPCS_CLK_RESET);
>  		val |= MAC_CLK_RESET_MAC | MAC_CLK_RESET_SD_RX |
> @@ -4529,7 +4530,8 @@ static int mvpp2_poll(struct napi_struct *napi, int budget)
>  	return rx_done;
>  }
>  
> -static void mvpp22_mode_reconfigure(struct mvpp2_port *port)
> +static void mvpp22_mode_reconfigure(struct mvpp2_port *port,
> +				    phy_interface_t interface)
>  {
>  	u32 ctrl3;
>  
> @@ -4540,18 +4542,18 @@ static void mvpp22_mode_reconfigure(struct mvpp2_port *port)
>  	mvpp22_pcs_reset_assert(port);
>  
>  	/* comphy reconfiguration */
> -	mvpp22_comphy_init(port);
> +	mvpp22_comphy_init(port, interface);
>  
>  	/* gop reconfiguration */
> -	mvpp22_gop_init(port);
> +	mvpp22_gop_init(port, interface);
>  
> -	mvpp22_pcs_reset_deassert(port);
> +	mvpp22_pcs_reset_deassert(port, interface);
>  
>  	if (mvpp2_port_supports_xlg(port)) {
>  		ctrl3 = readl(port->base + MVPP22_XLG_CTRL3_REG);
>  		ctrl3 &= ~MVPP22_XLG_CTRL3_MACMODESELECT_MASK;
>  
> -		if (mvpp2_is_xlg(port->phy_interface))
> +		if (mvpp2_is_xlg(interface))
>  			ctrl3 |= MVPP22_XLG_CTRL3_MACMODESELECT_10G;
>  		else
>  			ctrl3 |= MVPP22_XLG_CTRL3_MACMODESELECT_GMAC;
> @@ -4559,7 +4561,7 @@ static void mvpp22_mode_reconfigure(struct mvpp2_port *port)
>  		writel(ctrl3, port->base + MVPP22_XLG_CTRL3_REG);
>  	}
>  
> -	if (mvpp2_port_supports_xlg(port) && mvpp2_is_xlg(port->phy_interface))
> +	if (mvpp2_port_supports_xlg(port) && mvpp2_is_xlg(interface))
>  		mvpp2_xlg_max_rx_size_set(port);
>  	else
>  		mvpp2_gmac_max_rx_size_set(port);
> @@ -4579,7 +4581,7 @@ static void mvpp2_start_dev(struct mvpp2_port *port)
>  	mvpp2_interrupts_enable(port);
>  
>  	if (port->priv->hw_version >= MVPP22)
> -		mvpp22_mode_reconfigure(port);
> +		mvpp22_mode_reconfigure(port, port->phy_interface);
>  
>  	if (port->phylink) {
>  		phylink_start(port->phylink);
> @@ -6444,6 +6446,9 @@ static int mvpp2__mac_prepare(struct phylink_config *config, unsigned int mode,
>  			mvpp22_gop_mask_irq(port);
>  
>  			phy_power_off(port->comphy);
> +
> +			/* Reconfigure the serdes lanes */
> +			mvpp22_mode_reconfigure(port, interface);
>  		}
>  	}
>  
> @@ -6498,9 +6503,6 @@ static int mvpp2_mac_finish(struct phylink_config *config, unsigned int mode,
>  	    port->phy_interface != interface) {
>  		port->phy_interface = interface;
>  
> -		/* Reconfigure the serdes lanes */
> -		mvpp22_mode_reconfigure(port);
> -
>  		/* Unmask interrupts */
>  		mvpp22_gop_unmask_irq(port);
>  	}
> @@ -6961,7 +6963,7 @@ static int mvpp2_port_probe(struct platform_device *pdev,
>  	 * driver does this, we can remove this code.
>  	 */
>  	if (port->comphy) {
> -		err = mvpp22_comphy_init(port);
> +		err = mvpp22_comphy_init(port, port->phy_interface);
>  		if (err == 0)
>  			phy_power_off(port->comphy);
>  	}
> -- 
> 2.32.0
> 
> 

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