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From 5e448a17dfa2e95166534df7f677a3694ef6187d Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Tue, 29 Nov 2022 16:12:19 +0200
Subject: [PATCH 12/14] net: dpaa2-eth: serialize changes to priv->mac with a
 mutex

The dpaa2 architecture permits dynamic connections between objects on
the fsl-mc bus, specifically between a DPNI object (represented by a
struct net_device) and a DPMAC object (represented by a struct phylink).

The DPNI driver is notified when those connections are created/broken
through the dpni_irq0_handler_thread() method. To ensure that ethtool
operations, as well as netdev up/down operations serialize with the
connection/disconnection of the DPNI with a DPMAC,
dpni_irq0_handler_thread() takes the rtnl_lock() to block those other
operations from taking place.

There is code called by dpaa2_mac_connect() which wants to acquire the
rtnl_mutex once again, see phylink_create() -> phylink_register_sfp() ->
sfp_bus_add_upstream() -> rtnl_lock(). So the strategy doesn't quite
work out, even though it's fairly simple.

Create a different strategy, where all code paths in the dpaa2-eth
driver access priv->mac only while they are holding priv->mac_lock.
The phylink instance is not created or connected to the PHY under the
priv->mac_lock, but only assigned to priv->mac then. This will eliminate
the reliance on the rtnl_mutex.

Add lockdep annotations and put comments where holding the lock is not
necessary, and priv->mac can be dereferenced freely.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  | 43 ++++++++++++--
 .../net/ethernet/freescale/dpaa2/dpaa2-eth.h  |  6 ++
 .../ethernet/freescale/dpaa2/dpaa2-ethtool.c  | 58 +++++++++++++++----
 3 files changed, 91 insertions(+), 16 deletions(-)

--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -2020,8 +2020,11 @@ static int dpaa2_eth_link_state_update(s
 
        /* When we manage the MAC/PHY using phylink there is no need
         * to manually update the netif_carrier.
+        * We can avoid locking because we are called from the "link changed"
+        * IRQ handler, which is the same as the "endpoint changed" IRQ handler
+        * (the writer to priv->mac), so we cannot race with it.
         */
-       if (dpaa2_eth_is_type_phy(priv))
+       if (dpaa2_mac_is_type_phy(priv->mac))
                goto out;
 
        /* Chech link state; speed / duplex changes are not treated yet */
@@ -2060,6 +2063,8 @@ static int dpaa2_eth_open(struct net_dev
                           priv->dpbp_dev->obj_desc.id, priv->bpid);
        }
 
+       mutex_lock(&priv->mac_lock);
+
        if (!dpaa2_eth_is_type_phy(priv)) {
                /* We'll only start the txqs when the link is actually ready;
                 * make sure we don't race against the link up notification,
@@ -2078,6 +2083,7 @@ static int dpaa2_eth_open(struct net_dev
 
        err = dpni_enable(priv->mc_io, 0, priv->mc_token);
        if (err < 0) {
+               mutex_unlock(&priv->mac_lock);
                netdev_err(net_dev, "dpni_enable() failed\n");
                goto enable_err;
        }
@@ -2085,6 +2091,8 @@ static int dpaa2_eth_open(struct net_dev
        if (dpaa2_eth_is_type_phy(priv))
                dpaa2_mac_start(priv->mac);
 
+       mutex_unlock(&priv->mac_lock);
+
        return 0;
 
 enable_err:
@@ -2156,6 +2164,8 @@ static int dpaa2_eth_stop(struct net_dev
        int dpni_enabled = 0;
        int retries = 10;
 
+       mutex_lock(&priv->mac_lock);
+
        if (dpaa2_eth_is_type_phy(priv)) {
                dpaa2_mac_stop(priv->mac);
        } else {
@@ -2163,6 +2173,8 @@ static int dpaa2_eth_stop(struct net_dev
                netif_carrier_off(net_dev);
        }
 
+       mutex_unlock(&priv->mac_lock);
+
        /* On dpni_disable(), the MC firmware will:
         * - stop MAC Rx and wait for all Rx frames to be enqueued to software
         * - cut off WRIOP dequeues from egress FQs and wait until transmission
@@ -2488,12 +2500,20 @@ static int dpaa2_eth_ts_ioctl(struct net
 static int dpaa2_eth_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
 {
        struct dpaa2_eth_priv *priv = netdev_priv(dev);
+       int err;
 
        if (cmd == SIOCSHWTSTAMP)
                return dpaa2_eth_ts_ioctl(dev, rq, cmd);
 
-       if (dpaa2_eth_is_type_phy(priv))
-               return phylink_mii_ioctl(priv->mac->phylink, rq, cmd);
+       mutex_lock(&priv->mac_lock);
+
+       if (dpaa2_eth_is_type_phy(priv)) {
+               err = phylink_mii_ioctl(priv->mac->phylink, rq, cmd);
+               mutex_unlock(&priv->mac_lock);
+               return err;
+       }
+
+       mutex_unlock(&priv->mac_lock);
 
        return -EOPNOTSUPP;
 }
@@ -4453,7 +4473,9 @@ static int dpaa2_eth_connect_mac(struct
                        goto err_close_mac;
        }
 
+       mutex_lock(&priv->mac_lock);
        priv->mac = mac;
+       mutex_unlock(&priv->mac_lock);
 
        return 0;
 
@@ -4466,9 +4488,12 @@ err_free_mac:
 
 static void dpaa2_eth_disconnect_mac(struct dpaa2_eth_priv *priv)
 {
-       struct dpaa2_mac *mac = priv->mac;
+       struct dpaa2_mac *mac;
 
+       mutex_lock(&priv->mac_lock);
+       mac = priv->mac;
        priv->mac = NULL;
+       mutex_unlock(&priv->mac_lock);
 
        if (!mac)
                return;
@@ -4487,6 +4512,7 @@ static irqreturn_t dpni_irq0_handler_thr
        struct fsl_mc_device *dpni_dev = to_fsl_mc_device(dev);
        struct net_device *net_dev = dev_get_drvdata(dev);
        struct dpaa2_eth_priv *priv = netdev_priv(net_dev);
+       bool had_mac;
        int err;
 
        err = dpni_get_irq_status(dpni_dev->mc_io, 0, dpni_dev->mc_handle,
@@ -4504,7 +4530,12 @@ static irqreturn_t dpni_irq0_handler_thr
                dpaa2_eth_update_tx_fqids(priv);
 
                rtnl_lock();
-               if (dpaa2_eth_has_mac(priv))
+               /* We can avoid locking because the "endpoint changed" IRQ
+                * handler is the only one who changes priv->mac at runtime,
+                * so we are not racing with anyone.
+                */
+               had_mac = !!priv->mac;
+               if (had_mac)
                        dpaa2_eth_disconnect_mac(priv);
                else
                        dpaa2_eth_connect_mac(priv);
@@ -4605,6 +4636,8 @@ static int dpaa2_eth_probe(struct fsl_mc
        priv = netdev_priv(net_dev);
        priv->net_dev = net_dev;
 
+       mutex_init(&priv->mac_lock);
+
        priv->iommu_domain = iommu_get_domain_for_dev(dev);
 
        priv->tx_tstamp_type = HWTSTAMP_TX_OFF;
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h
@@ -580,6 +580,8 @@ struct dpaa2_eth_priv {
 #endif
 
        struct dpaa2_mac *mac;
+       /* Serializes changes to priv->mac */
+       struct mutex            mac_lock;
        struct workqueue_struct *dpaa2_ptp_wq;
        struct work_struct      tx_onestep_tstamp;
        struct sk_buff_head     tx_skbs;
@@ -733,11 +735,15 @@ static inline unsigned int dpaa2_eth_rx_
 
 static inline bool dpaa2_eth_is_type_phy(struct dpaa2_eth_priv *priv)
 {
+       lockdep_assert_held(&priv->mac_lock);
+
        return dpaa2_mac_is_type_phy(priv->mac);
 }
 
 static inline bool dpaa2_eth_has_mac(struct dpaa2_eth_priv *priv)
 {
+       lockdep_assert_held(&priv->mac_lock);
+
        return priv->mac ? true : false;
 }
 
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-ethtool.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-ethtool.c
@@ -86,11 +86,16 @@ static void dpaa2_eth_get_drvinfo(struct
 static int dpaa2_eth_nway_reset(struct net_device *net_dev)
 {
        struct dpaa2_eth_priv *priv = netdev_priv(net_dev);
+       int err = -EOPNOTSUPP;
+
+       mutex_lock(&priv->mac_lock);
 
        if (dpaa2_eth_is_type_phy(priv))
-               return phylink_ethtool_nway_reset(priv->mac->phylink);
+               err = phylink_ethtool_nway_reset(priv->mac->phylink);
+
+       mutex_unlock(&priv->mac_lock);
 
-       return -EOPNOTSUPP;
+       return err;
 }
 
 static int
@@ -98,10 +103,18 @@ dpaa2_eth_get_link_ksettings(struct net_
                             struct ethtool_link_ksettings *link_settings)
 {
        struct dpaa2_eth_priv *priv = netdev_priv(net_dev);
+       int err;
 
-       if (dpaa2_eth_is_type_phy(priv))
-               return phylink_ethtool_ksettings_get(priv->mac->phylink,
-                                                    link_settings);
+       mutex_lock(&priv->mac_lock);
+
+       if (dpaa2_eth_is_type_phy(priv)) {
+               err = phylink_ethtool_ksettings_get(priv->mac->phylink,
+                                                   link_settings);
+               mutex_unlock(&priv->mac_lock);
+               return err;
+       }
+
+       mutex_unlock(&priv->mac_lock);
 
        link_settings->base.autoneg = AUTONEG_DISABLE;
        if (!(priv->link_state.options & DPNI_LINK_OPT_HALF_DUPLEX))
@@ -116,11 +129,17 @@ dpaa2_eth_set_link_ksettings(struct net_
                             const struct ethtool_link_ksettings *link_settings)
 {
        struct dpaa2_eth_priv *priv = netdev_priv(net_dev);
+       int err = -EOPNOTSUPP;
 
-       if (!dpaa2_eth_is_type_phy(priv))
-               return -EOPNOTSUPP;
+       mutex_lock(&priv->mac_lock);
+
+       if (dpaa2_eth_is_type_phy(priv))
+               err = phylink_ethtool_ksettings_set(priv->mac->phylink,
+                                                   link_settings);
 
-       return phylink_ethtool_ksettings_set(priv->mac->phylink, link_settings);
+       mutex_unlock(&priv->mac_lock);
+
+       return err;
 }
 
 static void dpaa2_eth_get_pauseparam(struct net_device *net_dev,
@@ -129,11 +148,16 @@ static void dpaa2_eth_get_pauseparam(str
        struct dpaa2_eth_priv *priv = netdev_priv(net_dev);
        u64 link_options = priv->link_state.options;
 
+       mutex_lock(&priv->mac_lock);
+
        if (dpaa2_eth_is_type_phy(priv)) {
                phylink_ethtool_get_pauseparam(priv->mac->phylink, pause);
+               mutex_unlock(&priv->mac_lock);
                return;
        }
 
+       mutex_unlock(&priv->mac_lock);
+
        pause->rx_pause = dpaa2_eth_rx_pause_enabled(link_options);
        pause->tx_pause = dpaa2_eth_tx_pause_enabled(link_options);
        pause->autoneg = AUTONEG_DISABLE;
@@ -152,9 +176,17 @@ static int dpaa2_eth_set_pauseparam(stru
                return -EOPNOTSUPP;
        }
 
-       if (dpaa2_eth_is_type_phy(priv))
-               return phylink_ethtool_set_pauseparam(priv->mac->phylink,
-                                                     pause);
+       mutex_lock(&priv->mac_lock);
+
+       if (dpaa2_eth_is_type_phy(priv)) {
+               err = phylink_ethtool_set_pauseparam(priv->mac->phylink,
+                                                    pause);
+               mutex_unlock(&priv->mac_lock);
+               return err;
+       }
+
+       mutex_unlock(&priv->mac_lock);
+
        if (pause->autoneg)
                return -EOPNOTSUPP;
 
@@ -309,8 +341,12 @@ static void dpaa2_eth_get_ethtool_stats(
        }
        *(data + i++) = buf_cnt;
 
+       mutex_lock(&priv->mac_lock);
+
        if (dpaa2_eth_has_mac(priv))
                dpaa2_mac_get_ethtool_stats(priv->mac, data + i);
+
+       mutex_unlock(&priv->mac_lock);
 }
 
 static int dpaa2_eth_prep_eth_rule(struct ethhdr *eth_value, struct ethhdr *eth_mask,