linux-kernel - [RFC PATCH net-next 06/12] net: dsa: mt7530: do not set CPU port interfaces to PHY_INTERFACE_MODE

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Date:   Wed,  5 Apr 2023 23:38:53 +0300
From:   arinc9.unal@...il.com
To:     René van Dorst <opensource@...rst.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Daniel Golle <daniel@...rotopia.org>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Russell King <linux@...linux.org.uk>
Cc:     Arınç ÜNAL <arinc.unal@...nc9.com>,
        Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>,
        Richard van Schagen <richard@...terhints.com>,
        Richard van Schagen <vschagen@...com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        erkin.bozoglu@...ont.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: [RFC PATCH net-next 06/12] net: dsa: mt7530: do not set CPU port interfaces to PHY_INTERFACE_MODE_NA

From: Arınç ÜNAL <arinc.unal@...nc9.com>

There is no need to set priv->p5_interface and priv->p6_interface to
PHY_INTERFACE_MODE_NA on mt7530_setup() and mt7531_setup().

As Vladimir explained, in include/linux/phy.h we have:

typedef enum {
	PHY_INTERFACE_MODE_NA,

In lack of other initialiser, the first element of an enum gets the value 0
in C.

Then, "priv" is allocated by this driver with devm_kzalloc(), which means
that its entire memory is zero-filled. So priv->p5_interface and
priv->p6_interface are already set to 0, PHY_INTERFACE_MODE_NA.

There is no code path between the devm_kzalloc(), and the position in
mt7530_setup() and mt7531_setup() that would change the value of
priv->p5_interface or priv->p6_interface from 0.

The only place they are modified is mt753x_phylink_mac_config() but
mt753x_phylink_mac_config() runs after mt753x_setup(), as can be seen on
the code path below.

mt7530_probe()
   -> dsa_register_switch()
      -> dsa_switch_probe()
         -> dsa_tree_setup()
            -> dsa_tree_setup_switches()
               -> dsa_switch_setup()
                  -> ds->ops->setup(): mt753x_setup()
            -> dsa_tree_setup_ports()
               -> dsa_port_setup()
                  [...]
                  -> dsa_port_phylink_create()
                     [...]
                     -> phylink_mac_config()
                        -> pl->mac_ops->mac_config():
                           dsa_port_phylink_mac_config()
                           -> ds->ops->phylink_mac_config():
                              mt753x_phylink_mac_config()

Therefore, do not put 0 into a variable containing 0.

Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
---
 drivers/net/dsa/mt7530.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 8a47dcb96cdf..fc5428baa905 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -2247,8 +2247,6 @@ mt7530_setup(struct dsa_switch *ds)
 	val |= MHWTRAP_MANUAL;
 	mt7530_write(priv, MT7530_MHWTRAP, val);
 
-	priv->p6_interface = PHY_INTERFACE_MODE_NA;
-
 	/* Enable and reset MIB counters */
 	mt7530_mib_reset(ds);
 
@@ -2466,10 +2464,6 @@ mt7531_setup(struct dsa_switch *ds)
 	mt7530_rmw(priv, MT7531_GPIO_MODE0, MT7531_GPIO0_MASK,
 		   MT7531_GPIO0_INTERRUPT);
 
-	/* Let phylink decide the interface later. */
-	priv->p5_interface = PHY_INTERFACE_MODE_NA;
-	priv->p6_interface = PHY_INTERFACE_MODE_NA;
-
 	/* Enable PHY core PLL, since phy_device has not yet been created
 	 * provided for phy_[read,write]_mmd_indirect is called, we provide
 	 * our own mt7531_ind_mmd_phy_[read,write] to complete this
-- 
2.37.2