Re: [PATCH net-next v3 4/7] net: dsa: mt7530: move XTAL check to mt7530_setup()

["Arınç ÜNAL" <arinc.unal@arinc9.com>]

On 4.02.2024 17:18, Russell King (Oracle) wrote:
> On Sun, Feb 04, 2024 at 04:55:40PM +0300, Arınç ÜNAL wrote:
>> This is not about laziness. This is before patch 2:
>>
>> phylink_mac_ops :: mac_config() -> dsa_port_phylink_mac_config()
>> -> dsa_switch_ops :: phylink_mac_config() -> mt753x_phylink_mac_config()
>>     -> mt753x_mac_config()
>>        -> mt753x_info :: mac_port_config() -> mt7530_mac_config()
>>           -> mt7530_setup_port5()
>>     -> mt753x_pad_setup()
>>        -> mt753x_info :: pad_setup() -> mt7530_pad_clk_setup()
>>
>> This is after:
>>
>> phylink_mac_ops :: mac_config() -> dsa_port_phylink_mac_config()
>> -> dsa_switch_ops :: phylink_mac_config() -> mt753x_phylink_mac_config()
>>     -> mt753x_mac_config()
>>        -> mt753x_info :: mac_port_config() -> mt7530_mac_config()
>>           -> mt7530_setup_port5()
>>           -> mt7530_setup_port6()
>>
>> Patch 2 does not move mt7530_setup_port6() to be called from
>> phylink_mac_ops :: mac_config(), it already is. There is no valid reason to
>> reorder the patches.
>>
>> My response to Russell should've stated this instead of focusing on his
>> second sentence.
> 
> This patch moves the test for a 20MHz crystal to mt7530_setup(),
> which is something that is entirely orthogonal to patch 2, which
> can be done cleanly (I've just applied the patches in the original
> order and then reordered them:
> 
> 98c481f5d706 net: dsa: mt7530: do not clear config->supported_interfaces
> 93c6b53b17f4 net: dsa: mt7530: correct port capabilities of MT7988
> c9c6d4c51a1d net: dsa: mt7530: simplify mt7530_setup_port6() and change to void
> adfa948253e0 net: dsa: mt7530: remove pad_setup function pointer
> 57e21e6c2fc0 net: dsa: mt7530: call port 6 setup from mt7530_mac_config()
> 959a0f9323c8 net: dsa: mt7530: move XTAL check to mt7530_setup()
> 856ab64a22ef net: dsa: mt7530: empty default case on mt7530_setup_port5()
> 
> No problems. The end result is identical comparing the git tree at the
> original "move XTAL" patch with adfa948253e0.
> 
> Now, if we look at "net: dsa: mt7530: remove pad_setup function pointer"
> we can see that yes, the pad_setup() method was called from mac_confing,
> but this is the exact contents of that patch removing the callsite:
> 
> -               mt753x_pad_setup(ds, state);
> 
> This returns an integer, which may be an error code, which is ignored.
> Therefore, if the XTAL frequency check fires, and mt753x_pad_setup()
> returns an error, it is ignored today.
> 
> After "net: dsa: mt7530: call port 6 setup from mt7530_mac_config()"
> the renamed pad_setup() method is now called from mac_config() thusly:
> 
> +               ret = mt7530_setup_port6(priv->ds, interface);
> +               if (ret)
> +                       return ret;
> 
> So now the error checks cause mt7530_mac_config() to return an error
> which in turn causes mt753x_mac_config() to fail, and therefore
> mt753x_phylink_mac_config() has different behaviour.
> 
> So, patch 2 changes the driver behaviour in the case of a 20MHz XTAL,
> which is then changed again by patch 4.
> 
> It would be better to have only one change of behaviour by moving
> patch 4 before patch 2.

If the idea is to not bring any more error returns to mt753x_mac_config()
because the return code is actually checked for that, I should do a bit
more effort and put patch 5 before patch 2 as well, to live up to what you
originally requested. Because, to get rid of all error returns on
mt7530_setup_port6(), both "net: dsa: mt7530: move XTAL check to
mt7530_setup()" and "net: dsa: mt7530: simplify mt7530_setup_port6() and
change to void" patches are needed. After these patches, I can move
mt7530_setup_port6() to mt7530_mac_config() and there won't be any error
returns being brought under mt753x_mac_config().

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