Messages in this thread Patch in this message | | | From | Douglas Anderson <> | Subject | [PATCH 1/3] arm64: Disable GiC priorities on Mediatek devices w/ firmware issues | Date | Fri, 6 Oct 2023 15:15:51 -0700 |
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In commit 44bd78dd2b88 ("irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/ firmware issues") we added a method for detecting Mediatek devices with broken firmware and disabled pseudo-NMI. While that worked, it didn't address the problem at a deep enough level.
The fundamental issue with this broken firmware is that it's not saving and restoring several important GICR registers. The current list is believed to be: * GICR_NUM_IPRIORITYR * GICR_CTLR * GICR_ISPENDR0 * GICR_ISACTIVER0 * GICR_NSACR
Pseudo-NMI didn't work because it was the only thing (currently) in the kernel that relied on the broken registers, so forcing pseudo-NMI off was an effective fix. However, it could be observed that calling system_uses_irq_prio_masking() on these systems still returned "true". That caused confusion and led to the need for commit a07a59415217 ("arm64: smp: avoid NMI IPIs with broken MediaTek FW"). It's worried that the incorrect value returned by system_uses_irq_prio_masking() on these systems will continue to confuse future developers.
Let's fix the issue a little more completely by disabling IRQ priorities at a deeper level in the kernel. Once we do this we can revert some of the other bits of code dealing with this quirk.
Signed-off-by: Douglas Anderson <dianders@chromium.org> ---
arch/arm64/kernel/cpufeature.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 2806a2850e78..e35efab8efa9 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2094,9 +2094,30 @@ static int __init early_enable_pseudo_nmi(char *p) } early_param("irqchip.gicv3_pseudo_nmi", early_enable_pseudo_nmi); +static bool are_gic_priorities_broken(void) +{ + bool is_broken = false; + struct device_node *np; + + /* + * Detect broken Mediatek firmware that doesn't properly save and + * restore GIC priorities. + */ + np = of_find_compatible_node(NULL, NULL, "arm,gic-v3"); + if (np) { + is_broken = of_property_read_bool(np, "mediatek,broken-save-restore-fw"); + of_node_put(np); + } + + return is_broken; +} + static bool can_use_gic_priorities(const struct arm64_cpu_capabilities *entry, int scope) { + if (are_gic_priorities_broken()) + return false; + /* * ARM64_HAS_GIC_CPUIF_SYSREGS has a lower index, and is a boot CPU * feature, so will be detected earlier. -- 2.42.0.609.gbb76f46606-goog
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