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arm64: mm: Treat all devices as dma-coherent when CLIDR_EL1.LoC == 0

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On systems where CLIDR_EL1.LoC == 0, no cache maintenance is required
when cleaning or invalidating to the Point of Coherency and therefore
all DMA agents can be treated as coherent.

Extend arch_setup_dma_ops() to take CLIDR_EL1.LoC into account when
setting the DMA ops for a device, emitting a warning message if the
firmware advertises a non-coherent device on a fully coherent system.

Cc: Steffen Eiden <seiden@linux.ibm.com>
Cc: Andreas Grapentin <gra@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2026-07-23 14:03:21 +01:00
parent a13c140cc2
commit 233b5554e0
1 changed files with 5 additions and 0 deletions
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5
arch/arm64/mm/dma-mapping.c
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@ -42,6 +42,11 @@ void arch_setup_dma_ops(struct device *dev, bool coherent)
{
int cls = cache_line_size_of_cpu();
if (!coherent && !CLIDR_LOC(read_sysreg(clidr_el1))) {
dev_warn(dev, "CLIDR_EL1.LoC == 0, treating as coherent\n");
coherent = true;
}
WARN_TAINT(!coherent && cls > ARCH_DMA_MINALIGN,
TAINT_CPU_OUT_OF_SPEC,
"%s %s: ARCH_DMA_MINALIGN smaller than CTR_EL0.CWG (%d < %d)",