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

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Date:   Thu, 22 Oct 2020 11:14:03 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Chris Heally <cphealy@...il.com>, netdev@...r.kernel.org,
        Fugang Duan <fugang.duan@....com>
Subject: Re: [PATCH] net: ethernet: fec: Replace interrupt driven MDIO with
 polled IO

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