linux-kernel - Re: [PATCH v4] lpc32xx: Added ethernet driver: smp

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Message-ID: <4F55EA6D.3070602@antcom.de>
Date:	Tue, 06 Mar 2012 11:43:57 +0100
From:	Roland Stigge <stigge@...com.de>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	davem@...emloft.net, jeffrey.t.kirsher@...el.com,
	alexander.h.duyck@...el.com, eilong@...adcom.com,
	ian.campbell@...rix.com, netdev@...r.kernel.org,
	w.sang@...gutronix.de, linux-kernel@...r.kernel.org,
	kevin.wells@....com, linux-arm-kernel@...ts.infradead.org,
	arnd@...db.de, baruch@...s.co.il, joe@...ches.com
Subject: Re: [PATCH v4] lpc32xx: Added ethernet driver: smp_wmb()

On 03/05/2012 11:45 PM, Ben Hutchings wrote:
>> +	/* Clear and enable interrupts */
>> +	writel(0xFFFF, LPC_ENET_INTCLEAR(pldat->net_base));
>> +	lpc_eth_enable_int(pldat->net_base);
>> +
>> +	/* Get the next TX buffer output index */
>> +	pldat->num_used_tx_buffs = 0;
>> +	pldat->last_tx_idx =
>> +		readl(LPC_ENET_TXCONSUMEINDEX(pldat->net_base));
> 
> Doesn't this need to be done *before* enabling interrupts?  Also, I
> think you need an smp_wmb() so that the interrupt handler is guaranteed
> to see all these writes.

Do you mean _one_ smp_wmb() directly after lpc_eth_enable_int() (which
I'm moving behind the above code?

Note that there is no SMP in LPCs and NXP is not planning to build one
AFAIK. However, I'm fine with including smp_wmb() anyway for completeness.

Thanks in advance,

Roland
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