path: root/Documentation
diff options
authorThomas Petazzoni <thomas.petazzoni@free-electrons.com>2014-06-13 10:58:38 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-06-29 10:26:37 +0100
commit98ea2dba65932ffc456b6d7b11b8a0624e2f7b95 (patch)
treec08c7d850575c49865efc34380cda1d9bb2d028a /Documentation
parentb8d8772e53f83cc87aeeab1c3a60d5d5d45ce38b (diff)
ARM: 8076/1: mm: add support for HW coherent systems in PL310 cache
When a PL310 cache is used on a system that provides hardware coherency, the outer cache sync operation is useless, and can be skipped. Moreover, on some systems, it is harmful as it causes deadlocks between the Marvell coherency mechanism, the Marvell PCIe controller and the Cortex-A9. To avoid this, this commit introduces a new Device Tree property 'arm,io-coherent' for the L2 cache controller node, valid only for the PL310 cache. It identifies the usage of the PL310 cache in an I/O coherent configuration. Internally, it makes the driver disable the outer cache sync operation. Note that technically speaking, a fully coherent system wouldn't require any of the other .outer_cache operations. However, in practice, when booting secondary CPUs, these are not yet coherent, and therefore a set of cache maintenance operations are necessary at this point. This explains why we keep the other .outer_cache operations and only ->sync is disabled. While in theory any write to a PL310 register could cause the deadlock, in practice, disabling ->sync is sufficient to workaround the deadlock, since the other cache maintenance operations are only used in very specific situations. Contrary to previous versions of this patch, this new version does not simply NULL-ify the ->sync member, because the l2c_init_data structures are now 'const' and therefore cannot be modified, which is a good thing. Therefore, this patch introduces a separate l2c_init_data instance, called of_l2c310_coherent_data. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'Documentation')
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/arm/l2cc.txt b/Documentation/devicetree/bindings/arm/l2cc.txt
index b513cb8196fe..af527ee111c2 100644
--- a/Documentation/devicetree/bindings/arm/l2cc.txt
+++ b/Documentation/devicetree/bindings/arm/l2cc.txt
@@ -40,6 +40,9 @@ Optional properties:
- arm,filter-ranges : <start length> Starting address and length of window to
filter. Addresses in the filter window are directed to the M1 port. Other
addresses will go to the M0 port.
+- arm,io-coherent : indicates that the system is operating in an hardware
+ I/O coherent mode. Valid only when the arm,pl310-cache compatible
+ string is used.
- interrupts : 1 combined interrupt.
- cache-id-part: cache id part number to be used if it is not present
on hardware

Privacy Policy