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Having bit 22 cleared in the PL310 Auxiliary Control register (shared attribute override enable) has the side effect of transforming Normal Shared Non-cacheable reads into Cacheable no-allocate reads. Coherent DMA buffers in Linux always have a Cacheable alias via the kernel linear mapping and the processor can speculatively load cache lines into the PL310 controller. With bit 22 cleared, Non-cacheable reads would unexpectedly hit such cache lines leading to buffer corruption. This was inspired by a patch from Catalin Marinas [1] and also from recent discussions in the linux-arm-kernel list [2] where Russell King and Rob Herring suggested that bootloaders should initialize the cache. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2010-November/031810.html [2] https://lkml.org/lkml/2015/2/20/199 Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> |
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