Re: [PATCH 1/8] net: phy: Introduce Qualcomm IPQ5018 internal PHY driver

From: Ziyang Huang <hzyitc@outlook.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com,
	richardcochran@gmail.com, p.zabel@pengutronix.de,
	matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com,
	linux-kernel@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH 1/8] net: phy: Introduce Qualcomm IPQ5018 internal PHY driver
Date: Mon, 22 Jan 2024 23:37:29 +0800	[thread overview]
Message-ID: <TYZPR01MB5556D035D9A13962844BB553C9752@TYZPR01MB5556.apcprd01.prod.exchangelabs.com> (raw)
In-Reply-To: <2c6c0d72-5d4e-4ec4-beb6-d30852108a67@lunn.ch>

在 2024/1/22 0:19, Andrew Lunn 写道:
> On Sun, Jan 21, 2024 at 08:42:30PM +0800, Ziyang Huang wrote:
>> Signed-off-by: Ziyang Huang <hzyitc@outlook.com>
> 
> You need to say something in the commit message. One obvious thing is
> to justify not using the at803x driver, since

I want add more descriptions here. But I have no idea what to write. 
This is a mininal driver for a special phy.

Here is the thing, at first, I was tring to add these into at803x 
driver, then I found that the IPQ5018 internel phy is a special device. 
The initialization sequence is initing GCC clock and reset control, then 
registering clocks providers, which is very different from other devices.

What's more, I remembered it *wrongly* and thought it need to be 
accessed through MMIO. After checking the vendor code again, this 
doesn't exist.

So it seem like that it's a good idea to move it back to at803x driver.

> 
>> +#define IPQ5018_PHY_ID			0x004dd0c0
> 
> is in the Atheros OUI range.
> 
>> +static int ipq5018_probe(struct phy_device *phydev)
>> +{
>> +	struct ipq5018_phy *priv;
>> +	struct device *dev = &phydev->mdio.dev;
>> +	char name[64];
>> +	int ret;
> 
> I guess you are new to mainline network. Please read:
> 
> https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html
> 
> Section 1.6.4.

Sorry for missing it, will read it later.

> 
>> +
>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +	if (!priv)
>> +		return dev_err_probe(dev, -ENOMEM,
>> +				     "failed to allocate priv\n");
> 
> Please read the documentation of dev_err_probe() and this fix the
> obvious problem with this.

I had read it and I had known this helper function is to resolve the 
duplicate code for EPROBE_DEFER.

But it also say "Note that it is deemed acceptable to use this function 
for error prints during probe even if the @err is known to never be 
-EPROBE_DEFER. The benefit compared to a normal dev_err() is the 
standardized format of the error code and the fact that the error code 
is returned."

And I can find the same code in other driver, so I thought it is a 
standard. Or should I just return -ENOMEM? Please let me known.

> 
>> +	snprintf(name, sizeof(name), "%s#rx", dev_name(dev));
>> +	priv->clk_rx = clk_hw_register_fixed_rate(dev, name, NULL, 0,
>> +						  TX_RX_CLK_RATE);
>> +	if (IS_ERR_OR_NULL(priv->clk_rx))
>> +		return dev_err_probe(dev, PTR_ERR(priv->clk_rx),
>> +				     "failed to register rx clock\n");
>> +
>> +	snprintf(name, sizeof(name), "%s#tx", dev_name(dev));
>> +	priv->clk_tx = clk_hw_register_fixed_rate(dev, name, NULL, 0,
>> +						  TX_RX_CLK_RATE);
>> +	if (IS_ERR_OR_NULL(priv->clk_tx))
>> +		return dev_err_probe(dev, PTR_ERR(priv->clk_tx),
>> +				     "failed to register tx clock\n");
>> +
>> +	priv->clk_data = devm_kzalloc(dev,
>> +				      struct_size(priv->clk_data, hws, 2),
>> +				      GFP_KERNEL);
>> +	if (!priv->clk_data)
>> +		return dev_err_probe(dev, -ENOMEM,
>> +				     "failed to allocate clk_data\n");
>> +
>> +	priv->clk_data->num = 2;
>> +	priv->clk_data->hws[0] = priv->clk_rx;
>> +	priv->clk_data->hws[1] = priv->clk_tx;
>> +	ret = of_clk_add_hw_provider(dev->of_node, of_clk_hw_onecell_get,
>> +				     priv->clk_data);
>> +	if (ret)
>> +		return dev_err_probe(dev, ret,
>> +				     "fail to register clock provider\n");
> 
> This needs an explanation. Why register two fixed clocks, which you
> never use? Why not put these two clocks in DT?

Without documentions, here is my guess:

This is required by GCC controller. GCC driver require TX and RX clocks 
from GEPHY/UNIPHY. Then throught some sel or div cells, output clocks to 
GEPHY/UNIPHY and MAC. So I need to register them to make them can be 
refered in GCC controller. Will add a figure describing the clock tree 
in UNIPHY driver.

The frequency of these clocks is depends on the mode. For GEPHY, it only 
supports SGMII ( Or something similar, this is a internal bus ) and the 
clock is fixed at 1.25G. But for UNIPHY, is supports more mode like 
SGMII+ which used 3.125G.

> 
>> +
>> +	return 0;
>> +}
>> +
>> +static int ipq5018_soft_reset(struct phy_device *phydev)
>> +{
>> +	int ret;
>> +
>> +	ret = phy_modify(phydev, IPQ5018_PHY_FIFO_CONTROL,
>> +			 IPQ5018_PHY_FIFO_RESET, 0);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	msleep(50);
>> +
>> +	ret = phy_modify(phydev, IPQ5018_PHY_FIFO_CONTROL,
>> +			 IPQ5018_PHY_FIFO_RESET, IPQ5018_PHY_FIFO_RESET);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	return 0;
>> +}
> 
> This needs an explanation. It is also somewhat like
> qca808x_link_change_notify(). Is it really sufficient to only do this
> reset FIFO during a soft reset, or is it needed when ever the link
> changes?

I'm not sure here, this is what u-boot does. But I guess, we can reset 
GCC_GEPHY_* serial reset_controls.

> 
> You also appear to be missing device tree bindings.

Sorry for forgeting to add a WiP tag. Will add dt-bindings documentions 
in next patches.

> 
>      Andrew
> 
> ---
> pw-bot: cr
> 