Re: [PATCH v3 08/16] irqchip/gic: Configure SGIs as standard interrupts

[Jon Hunter]

On 16/09/2020 16:55, Marc Zyngier wrote:
> On 2020-09-16 16:46, Jon Hunter wrote:
>> On 16/09/2020 16:10, Marc Zyngier wrote:
>>> Hi Jon,
>>>
>>> +Linus, who is facing a similar issue.
>>>
>>> On 2020-09-16 15:16, Jon Hunter wrote:
>>>> Hi Marc,
>>>>
>>>> On 14/09/2020 14:06, Marek Szyprowski wrote:
>>>>> Hi Marc,
>>>>>
>>>>> On 01.09.2020 16:43, Marc Zyngier wrote:
>>>>>> Change the way we deal with GIC SGIs by turning them into proper
>>>>>> IRQs, and calling into the arch code to register the interrupt range
>>>>>> instead of a callback.
>>>>>>
>>>>>> Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>
>>>>>> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
>>>>> This patch landed in linux next-20200914 as commit ac063232d4b0
>>>>> ("irqchip/gic: Configure SGIs as standard interrupts"). Sadly it
>>>>> breaks
>>>>> booting of all Samsung Exynos 4210/4412 based boards (dual/quad ARM
>>>>> Cortex A9 based). Here are the last lines from the bootlog:
>>>>
>>>> I am observing the same thing on several Tegra boards (both arm and
>>>> arm64). Bisect is pointing to this commit. Reverting this alone does
>>>> not
>>>> appear to be enough to fix the issue.
>>>
>>> Right, I am just massively by the GICv3 spec, and failed to remember
>>> that ye olde GIC exposes the source CPU in AIR *and* wants it back,
>>> while
>>> newer GICs deal with that transparently.
>>>
>>> Can you try the patch below and let me know?
>>
>> Yes will do.
>>
>>> @@ -365,14 +354,13 @@ static void __exception_irq_entry
>>> gic_handle_irq(struct pt_regs *regs)
>>>              smp_rmb();
>>>
>>>              /*
>>> -             * Samsung's funky GIC encodes the source CPU in
>>> -             * GICC_IAR, leading to the deactivation to fail if
>>> -             * not written back as is to GICC_EOI.  Stash the
>>> -             * INTID away for gic_eoi_irq() to write back.
>>> -             * This only works because we don't nest SGIs...
>>> +             * The GIC encodes the source CPU in GICC_IAR,
>>> +             * leading to the deactivation to fail if not
>>> +             * written back as is to GICC_EOI.  Stash the INTID
>>> +             * away for gic_eoi_irq() to write back.  This only
>>> +             * works because we don't nest SGIs...
>>>               */
>>> -            if (is_frankengic())
>>> -                set_sgi_intid(irqstat);
>>> +            this_cpu_write(sgi_intid, intid);
>>
>> I assume that it should be irqstat here and not intid?
> 
> Indeed. As you can tell, I haven't even tried to compile it, sorry about
> that.

No worries, I got the gist. However, even with this change, it still
does not boot :-(

Jon

-- 
nvpublic