On Mon, Jul 27, 2015 at 04:26:05PM -0500, Nishanth Menon wrote:
Add workaround for Cortex-A15 ARM erratum 801819 which says in summary that "A livelock can occur in the L2 cache arbitration that might prevent a snoop from completing. Under certain conditions this can cause the system to deadlock. "
Recommended workaround is as follows: Do both of the following:
- Do not use the write-back no-allocate memory type.
- Do not issue write-back cacheable stores at any time when the cache
is disabled (SCTLR.C=0) and the MMU is enabled (SCTLR.M=1). Because it is implementation defined whether cacheable stores update the cache when the cache is disabled it is not expected that any portable code will execute cacheable stores when the cache is disabled.
For implementations of Cortex-A15 configured without the “L2 arbitration register slice” option (typically one or two core systems), you must also do the following:
- Disable write-streaming in each CPU by setting ACTLR[28:25] = 0b1111
So, we provide an option to disable write streaming on OMAP5 and DRA7. It is a rare condition to occur and may be enabled selectively based on platform acceptance of risk.
Applies to: A15 revisions r2p0, r2p1, r2p2, r2p3 or r2p4 and REVIDR[3] is set to 0.
Note: certain unicore SoCs *might* not have REVIDR[3] not set, but might not meet the condition for the erratum to occur when they donot have ACP (Accelerator Coherency Port) hooked to ACE (AXI Coherency Extensions). Such SoCs will need the work around handled in the SoC specific manner, since there is no ARM generic manner to detect such configurations.
Based on ARM errata Document revision 18.0 (22 Nov 2013)
Suggested-by: Richard Woodruff r-woodruff2@ti.com Suggested-by: Brad Griffis bgriffis@ti.com Reviewed-by: Brad Griffis bgriffis@ti.com Signed-off-by: Nishanth Menon nm@ti.com
Applied to u-boot/master, thanks!