netdev - Re: [EXT] Re: [PATCH] net: ethernet: fec: Replace interrupt driven MDIO with polled IO

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Date:   Tue, 27 Oct 2020 10:17:30 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Andy Duan <fugang.duan@....com>, Andrew Lunn <andrew@...n.ch>,
        Dave Karr <dkarr@...x.com>,
        Clemens Gruber <clemens.gruber@...ruber.com>
Cc:     Chris Heally <cphealy@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [EXT] Re: [PATCH] net: ethernet: fec: Replace interrupt driven
 MDIO with polled IO

Hi Andy,

On 22/10/20 7:04 pm, Andy Duan wrote:
> From: Greg Ungerer <gerg@...ux-m68k.org> Sent: Thursday, October 22, 2020 9:14 AM
>> Hi Andrew,
>>
>> On 21/10/20 11:37 pm, Andrew Lunn wrote:
>>>> +    if (fep->quirks & FEC_QUIRK_CLEAR_SETUP_MII) {
>>>> +            /* Clear MMFR to avoid to generate MII event by writing
>> MSCR.
>>>> +             * MII event generation condition:
>>>> +             * - writing MSCR:
>>>> +             *      - mmfr[31:0]_not_zero & mscr[7:0]_is_zero &
>>>> +             *        mscr_reg_data_in[7:0] != 0
>>>> +             * - writing MMFR:
>>>> +             *      - mscr[7:0]_not_zero
>>>> +             */
>>>> +            writel(0, fep->hwp + FEC_MII_DATA);
>>>> +    }
>>>
>>> Hi Greg
>>>
>>> The last time we discussed this, we decided that if you cannot do the
>>> quirk, you need to wait around for an MDIO interrupt, e.g. call
>>> fec_enet_mdio_wait() after setting FEC_MII_SPEED register.
>>>
>>>>
>>>>       writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED);
>>
>> The code following this is:
>>
>>           writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED);
>>
>>           /* Clear any pending transaction complete indication */
>>           writel(FEC_ENET_MII, fep->hwp + FEC_IEVENT);
>>
>>
>> So this is forcing a clear of the event here. Is that not good enough?
>>
>> For me on my ColdFire test target I always get a timeout if I wait for a
>> FEC_IEVENT after the FEC_MII_SPEED write.
>>
>> Regards
>> Greg
> 
> Dave Karr's last patch can fix the issue, but it may introduce 30ms delay during boot.
> Greg's patch is to add quirk flag to distinguish platform before clearing mmfr operation,
> which also can fix the issue.

Do you mean that we can use either fix - and that is ok for all hardware 
types?

Regards
Greg