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authorBen Hutchings <bhutchings@solarflare.com>2011-05-11 20:41:18 +0400
committerBen Hutchings <bhutchings@solarflare.com>2011-05-12 18:16:32 +0400
commit747df2258b1b9a2e25929ef496262c339c380009 (patch)
tree7f0ff222afed691599f24473e0b8d10b36f48cf2 /Documentation/aoe
parentff538818f4a82c4cf02d2d6bd6ac5c7360b9d41d (diff)
downloadlinux-747df2258b1b9a2e25929ef496262c339c380009.tar.xz
sfc: Always map MCDI shared memory as uncacheable
We enabled write-combining for memory-mapped registers in commit 65f0b417dee94f779ce9b77102b7d73c93723b39, but inhibited it for the MCDI shared memory where this is not supported. However, write-combining mappings also allow read-reordering, which may also be a problem. I found that when an SFC9000-family controller is connected to an Intel 3000 chipset, and write-combining is enabled, the controller stops responding to PCIe read requests during driver initialisation while the driver is polling for completion of an MCDI command. This results in an NMI and system hang. Adding read memory barriers between all reads to the shared memory area appears to reduce but not eliminate the probability of this. We have not yet established whether this is a bug in our BIU or in the PCIe bridge. For now, work around by mapping the shared memory area separately. Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
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