On Tue, Jul 06, 2021 at 02:29:07PM +0100, Robin Murphy wrote: > On 2021-07-06 11:26, Catalin Marinas wrote: > > On Tue, Jul 06, 2021 at 09:26:59AM +0000, Yassine Oudjana wrote: > > > In-Reply-To: <20210527124356.22367-1-will@xxxxxxxxxx> > > > > Reduce ARCH_DMA_MINALIGN to 64 bytes and allow the warning/taint to > > > > indicate if there are machines that unknowingly rely on this. > > > > > > The warning is being triggered on Qualcomm MSM8996, as well as the out-of-spec taint: > > > > Is this booting with ACPI or DT? > > > > > ------------[ cut here ]------------ > > > rtc-pm8xxx 400f000.qcom,spmi:pmic@0:rtc@6000: ARCH_DMA_MINALIGN smaller than CTR_EL0.CWG (64 < 128) > > > WARNING: CPU: 0 PID: 1 at arch/arm64/mm/dma-mapping.c:45 arch_setup_dma_ops+0xf8/0x10c > > [...] > > > This warning is triggered with nearly every driver probe, not only rtc-pm8xxx. > > > > I have a suspicion none of the reported devices actually do any DMA, so > > in practice it should be safe but we need to figure out why > > arch_setup_dma_ops() gets called. > > It gets called because there's no straightforward way to know that a > platform device *isn't* DMA-capable, so we have to assume they are. > > I would also assume that in a Qcom SoC there really are at least some things > doing non-coherent DMA :( Agreed, unless this is a CPU erratum and the line size is being reported for a cache beyond the PoC, then I think we're going to have to revert the patch reducing ARCH_DMA_MINALIGN after all. I can't find much information about the original Kryo core at all... Will
