From: Thomas Petazzoni Date: Thu, 13 Nov 2014 09:38:57 +0000 (+0100) Subject: ARM: mvebu: disable I/O coherency on non-SMP situations on Armada 370/375/38x/XP X-Git-Tag: omap-for-v3.19/fixes-for-merge-window~14^2~3^2~7 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e55355453600a33bb5ca4f71f2d7214875f3b061;p=pandora-kernel.git ARM: mvebu: disable I/O coherency on non-SMP situations on Armada 370/375/38x/XP Enabling the hardware I/O coherency on Armada 370, Armada 375, Armada 38x and Armada XP requires a certain number of conditions: - On Armada 370, the cache policy must be set to write-allocate. - On Armada 375, 38x and XP, the cache policy must be set to write-allocate, the pages must be mapped with the shareable attribute, and the SMP bit must be set Currently, on Armada XP, when CONFIG_SMP is enabled, those conditions are met. However, when Armada XP is used in a !CONFIG_SMP kernel, none of these conditions are met. With Armada 370, the situation is worse: since the processor is single core, regardless of whether CONFIG_SMP or !CONFIG_SMP is used, the cache policy will be set to write-back by the kernel and not write-allocate. Since solving this problem turns out to be quite complicated, and we don't want to let users with a mainline kernel known to have infrequent but existing data corruptions, this commit proposes to simply disable hardware I/O coherency in situations where it is known not to work. And basically, the is_smp() function of the kernel tells us whether it is OK to enable hardware I/O coherency or not, so this commit slightly refactors the coherency_type() function to return COHERENCY_FABRIC_TYPE_NONE when is_smp() is false, or the appropriate type of the coherency fabric in the other case. Thanks to this, the I/O coherency fabric will no longer be used at all in !CONFIG_SMP configurations. It will continue to be used in CONFIG_SMP configurations on Armada XP, Armada 375 and Armada 38x (which are multiple cores processors), but will no longer be used on Armada 370 (which is a single core processor). In the process, it simplifies the implementation of the coherency_type() function, and adds a missing call to of_node_put(). Signed-off-by: Thomas Petazzoni Fixes: e60304f8cb7bb545e79fe62d9b9762460c254ec2 ("arm: mvebu: Add hardware I/O Coherency support") Cc: # v3.8+ Acked-by: Gregory CLEMENT Link: https://lkml.kernel.org/r/1415871540-20302-3-git-send-email-thomas.petazzoni@free-electrons.com Signed-off-by: Jason Cooper --- Reading git-diff-tree failed