Messages in this thread | | | Date | Mon, 10 Feb 2014 16:38:09 +0000 | From | Ben Dooks <> | Subject | Re: [RFC PATCH] ARM: Add imprecise abort enable/disable macro |
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On 10/02/14 15:21, Dave Martin wrote: > On Mon, Feb 10, 2014 at 02:54:22PM +0000, Ben Dooks wrote: >> On 10/02/14 14:16, Dave Martin wrote: >>> On Fri, Feb 07, 2014 at 05:19:15PM +0100, Fabrice GASNIER wrote: >>>> This patch adds imprecise abort enable/disable macros. >>>> It also enables imprecise aborts when starting kernel. >>> >>> Relying on imprecise aborts for hardware probing would be considered bad >>> hardware and/or software design for ARM-specific stuff. >>> >>> PCI is more generic though, so we may have to put up with this to some >>> extent. Can you point me to the affected probing code? I'm not very >>> familiar with that stuff... >> >> The marvell pcie always had the option of delivering any bus >> errors as imprecise aborts. However it was /annoying/ and therefore > > You don't say ;) > >> easier just to turn it off and rely on the hardware returning 0xffff >> for any configuration area it couldn't get to. > > Does PCI have any way of finding out which parts of the configuration > space are there before you are forced to go poking around in invalid > address space? > > I'm guessing there may not be, otherwise this convsersation might not > be happening ... but I don't know too much about PCI.
IIRC for configuration accesses you have to wait for the PCIe core to get a response from the other end. The systems I've seen either poll for completion or hold the transaction until the pcie core has finished working.
-- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius
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