[RFC,v2,net-next,06/14] net: dsa: mt7530: do not set CPU port interfaces to PHY_INTERFACE_MODE_NA

Commit Message

Arınç ÜNAL April 7, 2023, 1:46 p.m. UTC

From: Arınç ÜNAL <[e-mail]>

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 <[e-mail]>
Signed-off-by: Arınç ÜNAL <[e-mail]>
---
 drivers/net/dsa/mt7530.c | 6 ------
 1 file changed, 6 deletions(-)

Comments

Vladimir Oltean April 11, 2023, 2:54 p.m. UTC | #1

On Fri, Apr 07, 2023 at 04:46:18PM +0300, [e-mail] wrote:
> From: Arınç ÜNAL <[e-mail]>
> 
> 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:
> 
> Therefore, do not put 0 into a variable containing 0.

The explanation is unnecessarily long. I only provided it to make sure
you understand.

Arınç ÜNAL April 12, 2023, 6:35 a.m. UTC | #2

On 11.04.2023 17:54, Vladimir Oltean wrote:
> On Fri, Apr 07, 2023 at 04:46:18PM +0300, [e-mail] wrote:
>> From: Arınç ÜNAL <[e-mail]>
>>
>> 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:
>>
>> Therefore, do not put 0 into a variable containing 0.
> 
> The explanation is unnecessarily long. I only provided it to make sure
> you understand.

I don't see a problem with a bit of verbosity on the patch log. It 
should make the reader understand the code path better.

Arınç

Patch

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