Re: [PATCH] Disable Bus Master on PCI device shutdown

[Andi Kleen]

Matthew Garrett <mjg@xxxxxxxxxx> writes:
>
> This protects against the case where a piece of hardware is continuing 
> to DMA even after the driver shutdown method has been called? I'm not 
> convinced this is safe. Some Broadcom parts will crash if busmastering 
> is disabled while they're still performing DMA, and they'll then hang 
> the bus if reenabled. There's also the risk that the hardware will start 
> DMAing again if it's reenabled after being shut down. It seems like 
> you're covering over the case where the driver didn't correctly quiesce 
> the hardware, but you risk triggering other bugs instead.

One alternative I've been pondering some time is to use AER link reset
instead. But this is mainly on servers, a lot of clients don't have it.

-Andi

-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only
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