Re: [PATCH v1 0/9] Fix Allwinner D1 boot regression

From: Samuel Holland <samuel.holland@sifive.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Emil Renner Berthing <emil.renner.berthing@canonical.com>,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Anup Patel <apatel@ventanamicro.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Daniel Lezcano <daniel.lezcano@linaro.org>
Subject: Re: [PATCH v1 0/9] Fix Allwinner D1 boot regression
Date: Thu, 15 Aug 2024 08:32:13 -0500	[thread overview]
Message-ID: <686d61c4-e7ac-4dca-a7fd-decdd72e84d9@sifive.com> (raw)
In-Reply-To: <87plqalyd4.ffs@tglx>

Hi Thomas, Emil,

On 2024-08-15 8:16 AM, Thomas Gleixner wrote:
> On Thu, Aug 15 2024 at 05:14, Emil Renner Berthing wrote:
>> Emil Renner Berthing wrote:
>>> 6.11-rc3 + these reverts:  https://us01.z.antigena.com/l/Er4kZWDmvL5-bLzHHJoZv0k71iwW2jCD5qNpiz0x0XdYY6oORF_nXh7U7jw6oubhi~32HI4i71jUW9v8~NvSvPeUWrdYx3WJBr2GPDUjOu6LYPCOBfR2dVQuMWvlNj4tDjXFp3QEQAmeawZflD4JrIJjtSYIbKfe6v-tgH7SEuHMeSSriU633Lv 
>>> 6.11-rc3 + Samuel's patch: https://us01.z.antigena.com/l/EULtAYky6ZvgqZ49KGS-WBsYTg~Ht1NoQtEYmUVb56ymS9jDagqYHLK90WDjnVt69GfB4IX5NSRQXmSfkNsTzB8lJmFvDihHQmGrsCv9FzlorD9yGfXDlQ6rG6vmn5BNDwlipmssGaOGfh9yko8n9ArWR4TLhEf~f9ODqme~NXXwA9DLLc9p 
>>
>> I think this confirms what Charlie found here:
>> https://lore.kernel.org/linux-riscv/ZoydV7vad5JWIcZb@ghost/
> 
> Yes. So the riscv timer is not working on this thing or it stops
> somehow.

That's correct. With the (firmware) devicetree that Emil is using, the OpenSBI
firmware does not have a timer device, so it does not expose the (optional[1])
SBI time extension, and sbi_set_timer() does nothing.

I wrote a patch (not submitted) to skip registering riscv_clock_event when the
SBI time extension is unavailable, but this doesn't fully solve the issue
either, because then we have no clockevent at all when
check_unaligned_access_all_cpus() is called.

How early in the boot process are we "required" to have a functional clockevent?
Do we need to refactor check_unaligned_access_all_cpus() so it works on systems
where the only clockevent is provided by a platform device?

Regards,
Samuel

[1] https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/src/intro.adoc

> Can you apply the debug patch below and check whether you see the
> 'J: ....' output at all and if so whether it stops at some point.
> 
> Thanks,
> 
>         tglx
> 
> ---
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -2459,6 +2459,9 @@ static void run_local_timers(void)
>  {
>  	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_LOCAL]);
>  
> +	if (!(jiffies & 0xFF))
> +		pr_info("J: %lx\n", jiffies);
> +
>  	hrtimer_run_queues();
>  
>  	for (int i = 0; i < NR_BASES; i++, base++) {
> 
> 
> 
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