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

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Message-ID: <CAJM55Z9kKqs-kMubsGsRkS6E2Y4ur1MmwD+1XFvGP=UVNrJvRg@mail.gmail.com>
Date: Thu, 15 Aug 2024 11:07:53 -0400
From: Emil Renner Berthing <emil.renner.berthing@...onical.com>
To: Samuel Holland <samuel.holland@...ive.com>, Anup Patel <apatel@...tanamicro.com>, 
	Thomas Gleixner <tglx@...utronix.de>, 
	Emil Renner Berthing <emil.renner.berthing@...onical.com>
Cc: linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v1 0/9] Fix Allwinner D1 boot regression

Samuel Holland wrote:
> On 2024-08-15 9:16 AM, Anup Patel wrote:
> > On Thu, Aug 15, 2024 at 7:41 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> >>
> >> On Thu, Aug 15 2024 at 08:32, Samuel Holland wrote:
> >>> On 2024-08-15 8:16 AM, Thomas Gleixner wrote:
> >>>> 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.
> >>
> >> Sigh. Does RISCV really have to repeat all mistakes which have been made
> >> by x86, ARM and others before? It's known for decades that the kernel
> >> relies on a working timer...
> >
> > My apologies for the delay in finding a fix for this issue.
> >
> > Almost all RISC-V platforms (except this one) have SBI Timer always
> > available and Linux uses a better timer or Sstc extension whenever
> > it is available.
>
> So this is the immediate solution: add the CLINT to the firmware devicetree so
> that the SBI time extension works, and Linux will boot without any code changes,
> albeit with a higher-overhead clockevent device.

But this will mean that you can't update your kernel to v6.9 or newer without
reflashing OpenSBI and u-boot. That's still a regression right?

/Emil