Re: [RFC PATCH] ARM: Add imprecise abort enable/disable macro

From: Ben Dooks
Date: Mon Feb 10 2014 - 11:38:21 EST


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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