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

From: Matthew Garrett
Date: Wed Jun 06 2012 - 16:10:05 EST


On Wed, Jun 06, 2012 at 12:42:07PM -0700, Eric W. Biederman wrote:

> pci_device_shutdown calls drv->shutdown before calling
> pci_device_disable. Which means that only devices that have trouble
> with this bit being flipped while DMA is ongoing and don't bother
> to stop their own DMA will have a problem.

drv->shutdown should already be quiescing the hardware. If it isn't, it
should be. If it is, what does this patch fix? Many drivers
call pci_enable_device() early enough that they clearly expect the
hardware to be quiescent when they do so, so this really does seem to
simply handle the kexec case without handling any other cases that could
be similarly problematic.

--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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