linux-kernel - Re: [PATCH 1/3] net: mdio-ipq4019: Add mdio reset function

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Date:   Mon, 02 Aug 2021 14:46:37 +0800
From:   luoj@...eaurora.org
To:     Andrew Lunn <andrew@...n.ch>
Cc:     hkallweit1@...il.com, davem@...emloft.net, kuba@...nel.org,
        p.zabel@...gutronix.de, agross@...nel.org,
        bjorn.andersson@...aro.org, robh+dt@...nel.org,
        robert.marko@...tura.hr, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, sricharan@...eaurora.org
Subject: Re: [PATCH 1/3] net: mdio-ipq4019: Add mdio reset function

On 2021-07-29 21:26, Andrew Lunn wrote:
> Hi Luo
> 
> For a patchset, netdev wants to see a patch 0/X which describes the
> big picture. What is the patchset as a whole doing.
> 
> Hi Andrew,
> Thanks for reminder, will provide it in the next patch set.
> 
>> +static int ipq_mdio_reset(struct mii_bus *bus)
>> +{
>> +	struct ipq4019_mdio_data *priv = bus->priv;
>> +	struct device *dev = bus->parent;
>> +	struct gpio_desc *reset_gpio;
>> +	u32 val;
>> +	int i, ret;
>> +
>> +	/* To indicate CMN_PLL that ethernet_ldo has been ready if needed */
>> +	if (!IS_ERR(priv->eth_ldo_rdy)) {
>> +		val = readl(priv->eth_ldo_rdy);
>> +		val |= BIT(0);
>> +		writel(val, priv->eth_ldo_rdy);
>> +		fsleep(QCA_PHY_SET_DELAY_US);
>> +	}
>> +
>> +	/* Reset GEPHY if need */
>> +	if (!IS_ERR(priv->reset_ctrl)) {
>> +		reset_control_assert(priv->reset_ctrl);
>> +		fsleep(QCA_PHY_SET_DELAY_US);
>> +		reset_control_deassert(priv->reset_ctrl);
>> +		fsleep(QCA_PHY_SET_DELAY_US);
>> +	}
> 
> What exactly is being reset here? Which is GEPHY?
> 
> The MDIO bus master driver should not be touching any Ethernet
> PHYs. All it provides is a bus, nothing more.
> 
> The GEPHY is the embedded Giga Ethernet PHY in the chipset IPQ50xx, 
> there is a dedicated MDIO bus for this internal PHY.
> what the reset function does here is for resetting this dedicated MDIO 
> bus and this embedded PHY DSP hardware.
> because this dedicated MDIO bus is only connected with this internal 
> PHY on chip set IPQ50xx, so i put this
> code in the MDIO reset function.
> 
>> +
>> +	/* Configure MDIO clock frequency */
>> +	if (!IS_ERR(priv->mdio_clk)) {
>> +		ret = clk_set_rate(priv->mdio_clk, QCA_MDIO_CLK_RATE);
>> +		if (ret)
>> +			return ret;
>> +
>> +		ret = clk_prepare_enable(priv->mdio_clk);
>> +		if (ret)
>> +			return ret;
>> +	}
> 
>> +
>> +	/* Reset PHYs by gpio pins */
>> +	for (i = 0; i < gpiod_count(dev, "phy-reset"); i++) {
>> +		reset_gpio = gpiod_get_index_optional(dev, "phy-reset", i, 
>> GPIOD_OUT_HIGH);
>> +		if (IS_ERR(reset_gpio))
>> +			continue;
>> +		gpiod_set_value_cansleep(reset_gpio, 0);
>> +		fsleep(QCA_PHY_SET_DELAY_US);
>> +		gpiod_set_value_cansleep(reset_gpio, 1);
>> +		fsleep(QCA_PHY_SET_DELAY_US);
>> +		gpiod_put(reset_gpio);
>> +	}
> 
> No, there is common code in phylib to do that.
> 
> Hi Andrew,
> The common code in phylib for resetting PHY by GPIO pin is high active, 
> which is not suitable for the PHY reset here.
> for resetting the PHY, calling gpiod_set_value_cansleep(reset_gpio, 1), 
> then gpiod_set_value_cansleep(reset_gpio, 0).
> but as for resetting the PHY by GPIO pin in IPQ chipset, this is the 
> opposite process(low active) from the phylib code,
> which needs to set the GPIO output value to 0, then to 1 for reset as 
> the code above.
> 
>>  static int ipq4019_mdio_probe(struct platform_device *pdev)
>>  {
>>  	struct ipq4019_mdio_data *priv;
>>  	struct mii_bus *bus;
>> +	struct resource *res;
>>  	int ret;
>> 
>>  	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*priv));
>> @@ -182,14 +244,23 @@ static int ipq4019_mdio_probe(struct 
>> platform_device *pdev)
>>  		return -ENOMEM;
>> 
>>  	priv = bus->priv;
>> +	priv->eth_ldo_rdy = IOMEM_ERR_PTR(-EINVAL);
>> 
>>  	priv->membase = devm_platform_ioremap_resource(pdev, 0);
>>  	if (IS_ERR(priv->membase))
>>  		return PTR_ERR(priv->membase);
>> 
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
>> +	if (res)
>> +		priv->eth_ldo_rdy = devm_ioremap_resource(&pdev->dev, res);
>> +
>> +	priv->reset_ctrl = devm_reset_control_get_exclusive(&pdev->dev, 
>> "gephy_mdc_rst");
>> +	priv->mdio_clk = devm_clk_get(&pdev->dev, "gcc_mdio_ahb_clk");
> 
> You probably want to use devm_clk_get_optional().
> 
>     Andrew
> 
> thanks for the comment, will update it in the next patch set.