netdev - Re: [PATCH net-next 1/4] drivers: net: xgene-v2: Add MDIO support

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Date:   Tue, 21 Mar 2017 16:18:46 -0700
From:   Iyappan Subramanian <isubramanian@....com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Laight <David.Laight@...lab.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>, patches <patches@....com>,
        Keyur Chudgar <kchudgar@....com>
Subject: Re: [PATCH net-next 1/4] drivers: net: xgene-v2: Add MDIO support

On Tue, Mar 21, 2017 at 1:35 PM, Andrew Lunn <andrew@...n.ch> wrote:
>> @@ -511,9 +512,9 @@ static int xge_close(struct net_device *ndev)
>>  {
>>       struct xge_pdata *pdata = netdev_priv(ndev);
>>
>> -     netif_carrier_off(ndev);
>>       netif_stop_queue(ndev);
>>       xge_mac_disable(pdata);
>> +     phy_stop(ndev->phydev);
>>
>>       xge_intr_disable(pdata);
>>       xge_free_irq(ndev);
>> @@ -683,9 +684,14 @@ static int xge_probe(struct platform_device *pdev)
>>       if (ret)
>>               goto err;
>>
>> +     spin_lock_init(&pdata->mdio_lock);
>> +
>
> ...
>
>> +static int xge_mdio_write(struct mii_bus *bus, int phy_id, int reg, u16 data)
>> +{
>> +     struct xge_pdata *pdata = bus->priv;
>> +     u32 done, val = 0;
>> +     u8 wait = 10;
>> +     int ret = 0;
>> +
>> +     spin_lock(&pdata->mdio_lock);
>> +
>> +     SET_REG_BITS(&val, PHY_ADDR, phy_id);
>> +     SET_REG_BITS(&val, REG_ADDR, reg);
>> +     xge_wr_csr(pdata, MII_MGMT_ADDRESS, val);
>> +
>> +     xge_wr_csr(pdata, MII_MGMT_CONTROL, data);
>> +     do {
>> +             usleep_range(5, 10);
>> +             done = xge_rd_csr(pdata, MII_MGMT_INDICATORS);
>> +     } while ((done & MII_MGMT_BUSY) && wait--);
>> +
>> +     if (done & MII_MGMT_BUSY) {
>> +             dev_err(&bus->dev, "MII_MGMT write failed\n");
>> +             ret = -ETIMEDOUT;
>> +     }
>> +
>> +     spin_unlock(&pdata->mdio_lock);
>> +
>> +     return ret;
>> +}
>> +
>> +static int xge_mdio_read(struct mii_bus *bus, int phy_id, int reg)
>> +{
>> +     struct xge_pdata *pdata = bus->priv;
>> +     u32 data, done, val = 0;
>> +     u8 wait = 10;
>> +
>> +     spin_lock(&pdata->mdio_lock);
>> +
>
> Hi Iyappan
>
> Please could you explain what this lock is protecting which the
> mii_bus mdio_lock in mdio_bus.c is not protecting?

Hi Keyur,

Please could you explain what this lock is protecting which the
mii_bus mdio_lock in mdio_bus.c is not protecting?

I agree with him.  Actually there is a mutex on mdio_bus.  So the mdio
bus read and write are locked.  we don't need the lock.

Do you agree ?


>
> Thanks
>         Andrew