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SubjectRe: [PATCH v4] lpc32xx: Added ethernet driver: smp_wmb()
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On Tue, 2012-03-06 at 11:43 +0100, Roland Stigge wrote:
> 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?

The sequence should be

pldat->state = values...;
smp_wmb();
enable_interrupts();

> Note that there is no SMP in LPCs and NXP is not planning to build one
> AFAIK.

Never say never!

> However, I'm fine with including smp_wmb() anyway for completeness.

Ben.

--
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.



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