linux-kernel - Re: [PATCH 1/1] net: macb: ensure ordering write to re-enable RX smoothly

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Message-ID: <554f7a31-887c-0b70-adf8-91a533af235b@windriver.com>
Date:   Mon, 28 Nov 2016 21:47:44 +0800
From:   Zumeng Chen <zumeng.chen@...driver.com>
To:     Nicolas Ferre <nicolas.ferre@...el.com>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH 1/1] net: macb: ensure ordering write to re-enable RX
 smoothly

On 2016年11月28日 17:22, Nicolas Ferre wrote:
> Le 28/11/2016 à 08:57, Zumeng Chen a écrit :
>> When a hardware issue happened as described by inline comments, the register
>> write pattern looks like the following:
>>
>>    <write ~MACB_BIT(RE)>
>>    + wmb();
>>    <write MACB_BIT(RE)>
>>
>> There might be a memory barrier between these two write operations, so add wmb
>> to ensure an flip from 0 to 1 for NCR.
>>
>> Signed-off-by: Zumeng Chen <zumeng.chen@...driver.com>
>> ---
>>   drivers/net/ethernet/cadence/macb.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
>> index 533653b..2f9c5b2 100644
>> --- a/drivers/net/ethernet/cadence/macb.c
>> +++ b/drivers/net/ethernet/cadence/macb.c
>> @@ -1156,6 +1156,7 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
>>   		if (status & MACB_BIT(RXUBR)) {
>>   			ctrl = macb_readl(bp, NCR);
>>   			macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
>> +			wmb();
>>   			macb_writel(bp, NCR, ctrl | MACB_BIT(RE));
>>   
>>   			if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE)
> It seems that there is exactly the same pattern in function
> at91ether_interrupt() can you fix both locations in your patch please?

Indeed, I'll send v2 soon, thanks Nicolas.

Although I only have the environment to re-produce the error report
as follows: "not whole frame pointed by descriptor" for macb_interrupt.

Cheers,
Zumeng

>
> Thanks, best regards,