* Serialization of configuration accesses for mvebu/designware
@ 2014-02-20 18:51 Andrew Murray
2014-02-20 20:42 ` Thomas Petazzoni
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Murray @ 2014-02-20 18:51 UTC (permalink / raw)
To: linux-pci@vger.kernel.org
Cc: Thomas Petazzoni, jg1.han, Jason Cooper, mohit.kumar
Hello,
I've noticed that the mvebu and designware both use spinlocks to
serialize access to the configuration space (pci_ops.[read|write]).
However the read/write ops are only ever used from the pci core
(access.c, pci.c) where they are already protected with the pci_lock.
As far as I can tell these extra spinlocks are superfluous, therefore...
Can they be removed?
Can future host bridge drivers assume that calls to the pci_ops are serialized?
I'm happy to provide a patch for the existing drivers if so.
Thanks,
Andrew Murray
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Serialization of configuration accesses for mvebu/designware
2014-02-20 18:51 Serialization of configuration accesses for mvebu/designware Andrew Murray
@ 2014-02-20 20:42 ` Thomas Petazzoni
0 siblings, 0 replies; 2+ messages in thread
From: Thomas Petazzoni @ 2014-02-20 20:42 UTC (permalink / raw)
To: Andrew Murray
Cc: linux-pci@vger.kernel.org, jg1.han, Jason Cooper, mohit.kumar
Dear Andrew Murray,
On Thu, 20 Feb 2014 18:51:32 +0000, Andrew Murray wrote:
> I've noticed that the mvebu and designware both use spinlocks to
> serialize access to the configuration space (pci_ops.[read|write]).
> However the read/write ops are only ever used from the pci core
> (access.c, pci.c) where they are already protected with the pci_lock.
>
> As far as I can tell these extra spinlocks are superfluous, therefore...
>
> Can they be removed?
> Can future host bridge drivers assume that calls to the pci_ops are serialized?
Just had a quick look, and indeed all the PCI configuration space
access functions in drivers/pci/access.c seem to be taking the
pci_lock, making the internal driver lock useless. Patches welcome! :-)
Thanks!
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
^ permalink raw reply [flat|nested] 2+ messages in thread
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