Re: [PATCH v2 1/2] arm64: Move Mediatek GIC quirk handling from irqchip to core
From: Marc Zyngier <maz@kernel.org>
Date: 2023-11-07 16:06:22
Also in:
linux-mediatek, lkml
On Tue, 07 Nov 2023 15:26:56 +0000, Douglas Anderson [off-list ref] wrote:
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.
This includes a partial revert of commit 44bd78dd2b88
("irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/ firmware
issues"). This isn't a full revert because it leaves some of the
changes to the "quirks" structure around in case future code needs it.
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>Acked-by: Marc Zyngier <maz@kernel.org> M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel