linux-kernel - Re: [PATCH v4 1/5] net: mdio: ipq4019: move eth_ldo

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Date: Wed, 3 Jan 2024 21:27:03 +0800
From: Jie Luo <quic_luoj@...cinc.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
CC: <agross@...nel.org>, <andersson@...nel.org>, <konrad.dybcio@...aro.org>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <andrew@...n.ch>, <hkallweit1@...il.com>, <robert.marko@...tura.hr>,
        <linux-arm-msm@...r.kernel.org>, <netdev@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_srichara@...cinc.com>
Subject: Re: [PATCH v4 1/5] net: mdio: ipq4019: move eth_ldo_rdy before MDIO
 bus register



On 1/3/2024 1:24 AM, Russell King (Oracle) wrote:
> On Mon, Dec 25, 2023 at 04:44:20PM +0800, Luo Jie wrote:
>> +/* Maximum SOC PCS(uniphy) number on IPQ platform */
>> +#define ETH_LDO_RDY_CNT				3
>> +
>>   struct ipq4019_mdio_data {
>> -	void __iomem	*membase;
>> -	void __iomem *eth_ldo_rdy;
>> +	void __iomem *membase;
>> +	void __iomem *eth_ldo_rdy[ETH_LDO_RDY_CNT];
> 
> Do you have any plans to make use of eth_ldo_rdy other than by code that
> you touch in this patch? If you don't, what is the point of storing
> these points in struct ipq4019_mdio_data ? You're using devm_ioremap()
> which will already store the pointer internally to be able to free the
> resource at the appropriate moment, so if your only use is shortly after
> devm_ioremap(), you can use a local variable for this... meaning this
> becomes (in addition to the other suggestion):

I will remove the eth_lod_rdy from the structure, which is only for
enabling LDO shortly, will update to use the local variable for this.
Thanks for review comments.

> 
>> +	/* This resource are optional */
>> +	for (index = 0; index < ETH_LDO_RDY_CNT; index++) {
>> +		res = platform_get_resource(pdev, IORESOURCE_MEM, index + 1);
>> +		if (res) {
>> +			priv->eth_ldo_rdy[index] = devm_ioremap(&pdev->dev,
>> +								res->start,
>> +								resource_size(res));
>> +
>> +			/* The ethernet LDO enable is necessary to reset PHY
>> +			 * by GPIO, some PHY(such as qca8084) GPIO reset uses
>> +			 * the MDIO level reset, so this function should be
>> +			 * called before the MDIO bus register.
>> +			 */
>> +			if (priv->eth_ldo_rdy[index]) {
>> +				u32 val;
>> +
>> +				val = readl(priv->eth_ldo_rdy[index]);
>> +				val |= BIT(0);
>> +				writel(val, priv->eth_ldo_rdy[index]);
>> +				fsleep(IPQ_PHY_SET_DELAY_US);
>> +			}
>> +		}
> 
> 		void __iomem *eth_ldo_rdy;
> 		u32 val;
> 
> 		res = platform_get_resource(pdev, IORESOURCE_MEM, index + 1);
> 		if (!res)
> 			break;
> 
> 		eth_ldo_rdy = devm_ioremap(&pdev->dev, res->start,
> 					   resource_size(res));
> 		if (!eth_ldo_rdy)
> 			continue;
> 
> 		val = readl(eth_ldo_rdy) | BIT(0);
> 		writel(val, eth_ldo_rdy);
> 		... whatever sleep is deemed required ...
> 
> Other issues:
> 
> 1. if devm_ioremap() fails (returns NULL) is it right that we should
>     just ignore that resource?

Since each LDO is independent, each LDO is for controlling the
independent Ethernet device, that should be fine to ignore the
failed resource.

> 
> 2. Do you need to sleep after each write, or will sleeping after
>     writing all of these do? It may be more efficient to detect when
>     we have at least one eth_ldo_rdy and then sleep once.
Yes, sleeping can be used after writing all of these, will update the
code as you suggest, thanks Russell.

> 
> Thanks.
>