On Thu, Sep 05 2019 at 18:39 -0600, Stephen Boyd wrote:
Quoting Lina Iyer (2019-08-29 11:11:51)
When an interrupt is to be serviced, the convention is to mask the
interrupt at the chip and unmask after servicing the interrupt. Enabling
and disabling the interrupt at the PDC irqchip causes an interrupt storm
due to the way dual edge interrupts are handled in hardware.
Skip configuring the PDC when the IRQ is masked and unmasked, instead
use the irq_enable/irq_disable callbacks to toggle the IRQ_ENABLE
register at the PDC. The PDC's IRQ_ENABLE register is only used during
the monitoring mode when the system is asleep and is not needed for
active mode detection.
I think this is saying that we want to always let the line be sent
through the PDC to the parent irqchip, in this case GIC, so that we
don't get an interrupt storm for dual edge interrupts? Why does dual
edge interrupts cause a problem?
I am not sure about the hardware details, but the PDC designers did not
expect enable and disable to be called whenever the interrupt is
handled. This specially becomes a problem for dual edge interrupts which
seems to generate a interrupt storm when enabled/disabled while handling
the interrupt.
--Lina
