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Date:   Fri, 11 Feb 2022 23:49:39 +0000
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     Jeremy Linton <jeremy.linton@arm.com>
Cc:     netdev@vger.kernel.org, mw@semihalf.com, davem@davemloft.net,
        kuba@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: mvpp2: Check for null pcs in mvpp2_acpi_start()
Message-ID: <Ygb2E1DGYVBO+mNP@shell.armlinux.org.uk>
References: <20220211234235.3180025-1-jeremy.linton@arm.com>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>
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On Fri, Feb 11, 2022 at 05:42:35PM -0600, Jeremy Linton wrote:
> Booting a MACCHIATObin with 5.17 the system OOPs with
> a null pointer deref when the network is started. This
> is caused by the pcs->ops structure being null on this
> particular platform/firmware.

pcs->ops should never be NULL. I'm surprised this fix results in any
kind of working networking.

Instead, the initialilsation of port->pcs_*.ops needs to be moved out
of the if (!mvpp2_use_acpi_compat_mode(..)) block. Please try this:

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index b45cc7bfcdb5..0fb65940c0a5 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -7036,6 +7036,9 @@ static int mvpp2_port_probe(struct platform_device *pdev,
 	dev->max_mtu = MVPP2_BM_JUMBO_PKT_SIZE;
 	dev->dev.of_node = port_node;
 
+	port->pcs_gmac.ops = &mvpp2_phylink_gmac_pcs_ops;
+	port->pcs_xlg.ops = &mvpp2_phylink_xlg_pcs_ops;
+
 	if (!mvpp2_use_acpi_compat_mode(port_fwnode)) {
 		port->phylink_config.dev = &dev->dev;
 		port->phylink_config.type = PHYLINK_NETDEV;
@@ -7106,9 +7109,6 @@ static int mvpp2_port_probe(struct platform_device *pdev,
 				  port->phylink_config.supported_interfaces);
 		}
 
-		port->pcs_gmac.ops = &mvpp2_phylink_gmac_pcs_ops;
-		port->pcs_xlg.ops = &mvpp2_phylink_xlg_pcs_ops;
-
 		phylink = phylink_create(&port->phylink_config, port_fwnode,
 					 phy_mode, &mvpp2_phylink_ops);
 		if (IS_ERR(phylink)) {

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!