[RFC PATCH net] net: dsa: mt7530: move PLL setup out of port 6 pad configuration

[Arınç ÜNAL]

On 7.03.2023 14:37, Vladimir Oltean wrote:
> On Tue, Mar 07, 2023 at 02:26:08PM +0300, Arınç ÜNAL wrote:
>> Port 5 as CPU port works fine with this patch. I completely removed from
>> port 6 phy modes.
>>
>> With your patch on MT7621 (remember port 5 always worked on MT7623):
>>
>> - Port 5 at rgmii as the only CPU port works, even though the PLL frequency
>> won't be set. The download/upload speed is not affected.
> 
> That's good. Empirically it seems to prove that ncpo1 only affects p6,
> which was my initial assumption.
> 
>> - port 6 at trgmii mode won't work if the PLL frequency is not set. The
>> SoC's MAC (gmac0) won't receive anything. It checks out since setting the
>> PLL frequency is put under the "Setup the MT7530 TRGMII Tx Clock" comment.
>> So port 6 cannot properly transmit frames to the SoC's MAC.
>>
>> - Port 6 at rgmii mode works without setting the PLL frequency. Speed is not
>> affected.
>>
>> I commented out core_write(priv, CORE_PLL_GROUP5,
>> RG_LCDDS_PCW_NCPO1(ncpo1)); to stop setting the PLL frequency.
>>
>> In conclusion, setting the PLL frequency is only needed for the trgmii mode,
>> so I believe we can get rid of it on other cases.
> 
> Got it, sounds expected, then? My patch can be submitted as-is, correct?

Yup, your patch is a go! I can submit other patches to address the 
incorrect comment regarding port 5, and remove ncpo1 from rgmii mode for 
port 6.

> 
>> One more thing, on MT7621, xtal matches to both HWTRAP_XTAL_40MHZ and
>> HWTRAP_XTAL_25MHZ so the final value of ncpo1 is 0x0a00. I'm not sure if
>> xtal matching both of them is the expected behaviour.
>>
>>> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
>>> index fbf27d4ab5d9..12cea89ae0ac 100644
>>> --- a/drivers/net/dsa/mt7530.c
>>> +++ b/drivers/net/dsa/mt7530.c
>>> @@ -439,8 +439,12 @@ mt7530_pad_clk_setup(struct dsa_switch *ds, phy_interface_t interface)
>>>   			/* PLL frequency: 150MHz: 1.2GBit */
>>>   			if (xtal == HWTRAP_XTAL_40MHZ)
>>>   				ncpo1 = 0x0780;
>>> +				dev_info(priv->dev, "XTAL is 40MHz, ncpo1 is 0x0780\n");
> 
> In the C language, you need to put brackets { } around multi-statement
> "if" blocks. Otherwise, despite the indentation, "dev_info" will be
> executed unconditionally (unlike in Python for example). There should
> also be a warning with newer gcc compilers about the misleading
> indentation not leading to the expected code.
> 
> Like this:
> 
> 			if (xtal == HWTRAP_XTAL_40MHZ) {
> 				ncpo1 = 0x0780;
> 				dev_info(priv->dev, "XTAL is 40MHz, ncpo1 is 0x0780\n");
> 			}
> 

Oh that figures, thanks a bunch. Clearly I've got a lot to learn. Now I 
see only 40MHz.

[    0.763772] mt7530 mdio-bus:1f: XTAL is 40MHz, ncpo1 is 0x0780

>>>   			if (xtal == HWTRAP_XTAL_25MHZ)
>>>   				ncpo1 = 0x0a00;
>>> +				dev_info(priv->dev, "XTAL is 25MHz, ncpo1 is 0x0a00\n");
>>> +			if (xtal == HWTRAP_XTAL_20MHZ)
>>> +				dev_info(priv->dev, "XTAL is 20MHz too\n");
>>>   		} else { /* PLL frequency: 250MHz: 2.0Gbit */
>>>   			if (xtal == HWTRAP_XTAL_40MHZ)
>>>   				ncpo1 = 0x0c80;
>>
>>> [    0.710455] mt7530 mdio-bus:1f: MT7530 adapts as multi-chip module
>>> [    0.734419] mt7530 mdio-bus:1f: configuring for fixed/rgmii link mode
>>> [    0.741766] mt7530 mdio-bus:1f: Link is Up - 1Gbps/Full - flow control rx/tx
>>> [    0.743647] mt7530 mdio-bus:1f: configuring for fixed/trgmii link mode
>>> [    0.755422] mt7530 mdio-bus:1f: XTAL is 40MHz, ncpo1 is 0x0780
>>> [    0.761250] mt7530 mdio-bus:1f: XTAL is 25MHz, ncpo1 is 0x0a00
>>> [    0.769414] mt7530 mdio-bus:1f: Link is Up - 1Gbps/Full - flow control rx/tx
>>> [    0.772067] mt7530 mdio-bus:1f lan1 (uninitialized): PHY [mt7530-0:00] driver [MediaTek MT7530 PHY] (irq=17)
>>> [    0.788647] mt7530 mdio-bus:1f lan2 (uninitialized): PHY [mt7530-0:01] driver [MediaTek MT7530 PHY] (irq=18)
>>> [    0.800354] mt7530 mdio-bus:1f lan3 (uninitialized): PHY [mt7530-0:02] driver [MediaTek MT7530 PHY] (irq=19)
>>> [    0.812031] mt7530 mdio-bus:1f lan4 (uninitialized): PHY [mt7530-0:03] driver [MediaTek MT7530 PHY] (irq=20)
>>> [    0.823418] mtk_soc_eth 1e100000.ethernet eth1: entered promiscuous mode
>>> [    0.830250] mtk_soc_eth 1e100000.ethernet eth0: entered promiscuous mode
>>> [    0.837007] DSA: tree 0 setup
>>
>> Thunderbird limits lines to about 72 columns, so I'm pasting as quotation
>> which seems to bypass that.
> 
> That seems to have worked, but shouldn't have been needed. I've uninstalled
> Thunderbird in favor of mutt + vim for email editing.. although, isn't
> there a Word Wrap option which you can just turn off?

It turns out there is indeed:

https://support.mozilla.org/en-US/questions/1307935

Mutt seems to be too techy for my taste but one can't know until they 
try it, thanks for the info.

Arınç