linux-kernel - Re: [PATCH 11/14] drivers: net: dsa: qca8k: apply switch revision fix

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Date:   Sat, 24 Apr 2021 18:09:27 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/14] drivers: net: dsa: qca8k: apply switch revision fix



On 4/24/2021 2:18 PM, Ansuel Smith wrote:
> On Thu, Apr 22, 2021 at 07:02:37PM -0700, Florian Fainelli wrote:
>>
>>
>> On 4/22/2021 6:47 PM, Ansuel Smith wrote:
>>> qca8k require special debug value based on the switch revision.
>>>
>>> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
>>> ---
>>>  drivers/net/dsa/qca8k.c | 23 +++++++++++++++++++++--
>>>  1 file changed, 21 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
>>> index 193c269d8ed3..12d2c97d1417 100644
>>> --- a/drivers/net/dsa/qca8k.c
>>> +++ b/drivers/net/dsa/qca8k.c
>>> @@ -909,7 +909,7 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
>>>  {
>>>  	const struct qca8k_match_data *data;
>>>  	struct qca8k_priv *priv = ds->priv;
>>> -	u32 reg, val;
>>> +	u32 phy, reg, val;
>>>  
>>>  	/* get the switches ID from the compatible */
>>>  	data = of_device_get_match_data(priv->dev);
>>> @@ -928,7 +928,26 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
>>>  	case 3:
>>>  	case 4:
>>>  	case 5:
>>> -		/* Internal PHY, nothing to do */
>>> +		/* Internal PHY, apply revision fixup */
>>> +		phy = qca8k_port_to_phy(port) % PHY_MAX_ADDR;
>>> +		switch (priv->switch_revision) {
>>> +		case 1:
>>> +			/* For 100M waveform */
>>> +			qca8k_phy_dbg_write(priv, phy, 0, 0x02ea);
>>> +			/* Turn on Gigabit clock */
>>> +			qca8k_phy_dbg_write(priv, phy, 0x3d, 0x68a0);
>>> +			break;
>>> +
>>> +		case 2:
>>> +			qca8k_phy_mmd_write(priv, phy, 0x7, 0x3c, 0x0);
>>> +			fallthrough;
>>> +		case 4:
>>> +			qca8k_phy_mmd_write(priv, phy, 0x3, 0x800d, 0x803f);
>>> +			qca8k_phy_dbg_write(priv, phy, 0x3d, 0x6860);
>>> +			qca8k_phy_dbg_write(priv, phy, 0x5, 0x2c46);
>>> +			qca8k_phy_dbg_write(priv, phy, 0x3c, 0x6000);
>>> +			break;
>>
>> This would be better done with a PHY driver that is specific to the
>> integrated PHY found in these switches, it would provide a nice clean
>> layer and would allow you to expose additional features like cable
>> tests, PHY statistics/counters, etc.
> 
> I'm starting to do some work with this and a problem arised. Since these
> value are based on the switch revision, how can I access these kind of
> data from the phy driver? It's allowed to declare a phy driver in the
> dsa directory? (The idea would be to create a qca8k dir with the dsa
> driver and the dedicated internal phy driver.) This would facilitate the
> use of normal qca8k_read/write (to access the switch revision from the
> phy driver) using common function?

The PHY driver should live under drivers/net/phy/ and if you need to
communicate the switch revision to the PHY driver you can use
phydev->dev_flags and implement a dsa_switch_ops::get_phy_flags()
callback and define a custom bitmask.

As far as the read/write operations if your switch implements a custom
mii_bus for the purpose of doing all of the underlying indirect register
accesses, then you should be fine. A lot of drivers do that however if
you want an example of both (communicating something to the PHY driver
and having a custom MII bus) you can look at drivers/net/dsa/bcm_sf2.c
for an example.
-- 
Florian