Re: [PATCH] irqchip/versatile-fpga: Handle chained IRQs properly

[Sungbo Eo]

Hi Marc,

On 2020-03-19 02:48, Marc Zyngier wrote:
> Hi Sungbo,
>
> On 2020-03-18 17:09, Sungbo Eo wrote:
> > Enclose the chained handler with chained_irq_{enter,exit}(), so that the
> > muxed interrupts get properly acked.
> >
> > This patch also fixes a reboot bug on OX820 SoC, where the jiffies timer
> > interrupt is never acked. The kernel waits a clock tick forever in
> > calibrate_delay_converge(), which leads to a boot hang.
>
> Nice catch.
>
> > Signed-off-by: Sungbo Eo <mans0n@xxxxxxxxxx>
> > Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> > ---
> > Âdrivers/irqchip/irq-versatile-fpga.c | 9 ++++++++-
> > Â1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/irqchip/irq-versatile-fpga.c
> > b/drivers/irqchip/irq-versatile-fpga.c
> > index 928858dada75..08faab2fec3e 100644
> > --- a/drivers/irqchip/irq-versatile-fpga.c
> > +++ b/drivers/irqchip/irq-versatile-fpga.c
> > @@ -6,6 +6,7 @@
> > Â#include <linux/irq.h>
> > Â#include <linux/io.h>
> > Â#include <linux/irqchip.h>
> > +#include <linux/irqchip/chained_irq.h>
> > Â#include <linux/irqchip/versatile-fpga.h>
> > Â#include <linux/irqdomain.h>
> > Â#include <linux/module.h>
> > @@ -68,12 +69,15 @@ static void fpga_irq_unmask(struct irq_data *d)
> >
> > Âstatic void fpga_irq_handle(struct irq_desc *desc)
> > Â{
> > +ÂÂÂ struct irq_chip *chip = irq_desc_get_chip(desc);
> > ÂÂÂÂ struct fpga_irq_data *f = irq_desc_get_handler_data(desc);
> > ÂÂÂÂ u32 status = readl(f->base + IRQ_STATUS);
> >
> > +ÂÂÂ chained_irq_enter(chip, desc);
> > +
>
> It's probably not a big deal, but I'm not fond of starting talking to
> the muxing irqchip before having done the chained_irq_enter() call.
>
> Moving that read here would probably be safer.

Oops, I missed it. Thanks for pointing it out.

> > ÂÂÂÂ if (status == 0) {
> > ÂÂÂÂÂÂÂÂ do_bad_IRQ(desc);
> > -ÂÂÂÂÂÂÂ return;
> > +ÂÂÂÂÂÂÂ goto out;
> > ÂÂÂÂ }
> >
> > ÂÂÂÂ do {
> > @@ -82,6 +86,9 @@ static void fpga_irq_handle(struct irq_desc *desc)
> > ÂÂÂÂÂÂÂÂ status &= ~(1 << irq);
> > ÂÂÂÂÂÂÂÂ generic_handle_irq(irq_find_mapping(f->domain, irq));
> > ÂÂÂÂ } while (status);
> > +
> > +out:
> > +ÂÂÂ chained_irq_exit(chip, desc);
> > Â}
> >
> > Â/*
>
> Otherwise looks good. If you send it again with the above fixed
> and a Fixes: tag, I'll queue it.

It seems the handler had been broken from the very beginning. Could you 
give me a hint on how the tag should be like?

Thanks.

> Thanks,
>
>  ÂÂÂÂÂÂÂ M.