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Message-ID: <4fa2ff0d-2804-4a58-980f-162e62b3dc9c@arinc9.com>
Date: Sun, 4 Feb 2024 18:55:14 +0300
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Subject: Re: [PATCH net-next v3 4/7] net: dsa: mt7530: move XTAL check to
 mt7530_setup()
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To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Daniel Golle <daniel@makrotopia.org>, DENG Qingfang <dqfext@gmail.com>,
 Sean Wang <sean.wang@mediatek.com>, Andrew Lunn <andrew@lunn.ch>,
 Florian Fainelli <f.fainelli@gmail.com>, Vladimir Oltean
 <olteanv@gmail.com>, "David S. Miller" <davem@davemloft.net>,
 Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
 Paolo Abeni <pabeni@redhat.com>, Matthias Brugger <matthias.bgg@gmail.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>,
 mithat.guner@xeront.com, erkin.bozoglu@xeront.com,
 Bartel Eerdekens <bartel.eerdekens@constell8.be>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 linux-mediatek@lists.infradead.org
References: <20240202-for-netnext-mt7530-improvements-2-v3-0-63d5adae99ca@arinc9.com>
 <20240202-for-netnext-mt7530-improvements-2-v3-4-63d5adae99ca@arinc9.com>
 <ZbzWpmZrukknMsYf@shell.armlinux.org.uk>
 <5b744f7f-2f63-4219-a0e9-8f08267b1fdd@arinc9.com>
 <Zb021ozEQSbU-gPd@makrotopia.org>
 <f6234b46-ce30-4b2a-9681-15633a06feff@arinc9.com>
 <Zb+ctEe9TVA3zhv8@shell.armlinux.org.uk>
From: =?UTF-8?B?QXLEsW7DpyDDnE5BTA==?= <arinc.unal@arinc9.com>
In-Reply-To: <Zb+ctEe9TVA3zhv8@shell.armlinux.org.uk>
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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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