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

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Date:   Wed, 16 Sep 2020 17:28:42 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Sumit Garg <sumit.garg@...aro.org>, linus.walleij@...aro.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King <linux@....linux.org.uk>,
        Jason Cooper <jason@...edaemon.net>,
        Saravana Kannan <saravanak@...gle.com>,
        Andrew Lunn <andrew@...n.ch>,
        Catalin Marinas <catalin.marinas@....com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Will Deacon <will@...nel.org>,
        'Linux Samsung SOC' <linux-samsung-soc@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
        Valentin Schneider <Valentin.Schneider@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v3 08/16] irqchip/gic: Configure SGIs as standard
 interrupts

On 2020-09-16 17:22, Marc Zyngier wrote:
> On 2020-09-16 16:58, Jon Hunter wrote:
>> 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@....com>
>>>>>>>> Signed-off-by: Marc Zyngier <maz@...nel.org>
>>>>>>> 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 :-(
> 
> Do you boot form EL2? If so, you'd also need this:
> 
>  static void gic_eoimode1_eoi_irq(struct irq_data *d)
>  {
> +	u32 hwirq = gic_irq(d);
> +
>  	/* Do not deactivate an IRQ forwarded to a vcpu. */
>  	if (irqd_is_forwarded_to_vcpu(d))
>  		return;
> 
> +	if (hwirq < 16)
> +		hwirq = this_cpu_read(sgi_intid);
> +
>  	writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_DEACTIVATE);
>  }

Make it that instead:

  static void gic_eoimode1_eoi_irq(struct irq_data *d)
  {
+	u32 hwirq = gic_irq(d);
+
  	/* Do not deactivate an IRQ forwarded to a vcpu. */
  	if (irqd_is_forwarded_to_vcpu(d))
  		return;

-	writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_DEACTIVATE);
+	if (hwirq < 16)
+		hwirq = this_cpu_read(sgi_intid);
+
+	writel_relaxed(hwirq, gic_cpu_base(d) + GIC_CPU_DEACTIVATE);
  }


         M.
-- 
Jazz is not dead. It just smells funny...