linux-kernel - Re: [PATCH 5/6] net: stmmac: add mdio clause 45 access from mac device for dwmac4

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Message-ID: <20190428163705.GH23059@lunn.ch>
Date:   Sun, 28 Apr 2019 18:37:05 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Biao Huang <biao.huang@...iatek.com>
Cc:     Jose Abreu <joabreu@...opsys.com>, davem@...emloft.net,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, yt.shen@...iatek.com,
        jianguo.zhang@...iatek.com
Subject: Re: [PATCH 5/6] net: stmmac: add mdio clause 45 access from mac
 device for dwmac4

On Sun, Apr 28, 2019 at 02:30:08PM +0800, Biao Huang wrote:
> +static int stmmac_c45_read(struct mii_bus *bus, int phyaddr,
> +			   int devad, int prtad)
> +{
> +	struct net_device *ndev = bus->priv;
> +	struct stmmac_priv *priv = netdev_priv(ndev);
> +	unsigned int mii_address = priv->hw->mii.addr;
> +	unsigned int mii_data = priv->hw->mii.data;
> +	u32 v, value;
> +	int data;
> +
> +	if (readl_poll_timeout(priv->ioaddr + mii_address, v, !(v & MII_BUSY),
> +			       100, 10000))
> +		return -EBUSY;

Hi Biao

readl_poll_timeout() returns an error code. It is better to return
that, than make up some other error code. Yes, i know the C22 read
returns EBUSY, but we don't need to copy that behaviour into C45.

> +
> +	value = 0;
> +	value |= (prtad << priv->hw->mii.cl45_reg_shift)
> +			& priv->hw->mii.cl45_reg_mask;
> +	writel(value, priv->ioaddr + mii_data);
> +
> +	/* delay 2ms to avoid error value of get_phy_c45_devs_in_pkg */
> +	mdelay(2);

Please could you explain this a bit more?

       Andrew