linux-kernel - Re: arm64: csdlock at early boot due to slow serial (?)

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Message-ID: <20250703114557.GD1039028@e132581.arm.com>
Date: Thu, 3 Jul 2025 12:45:57 +0100
From: Leo Yan <leo.yan@....com>
To: Breno Leitao <leitao@...ian.org>
Cc: cov@...eaurora.org, rmk+kernel@...linux.org.uk, mark.rutland@....com,
	catalin.marinas@....com, linux-serial@...r.kernel.org,
	rmikey@...a.com, linux-arm-kernel@...ts.infradead.org,
	usamaarif642@...il.com, linux-kernel@...r.kernel.org,
	paulmck@...nel.org
Subject: Re: arm64: csdlock at early boot due to slow serial (?)

On Thu, Jul 03, 2025 at 03:02:39AM -0700, Breno Leitao wrote:

[...]

> > In some cases, if normal world and secure world share the same UART
> > port, it can cause the UART state machine malfunction and long wait.
> 
> I don't know how to check it for sure, but, looking at the serial
> console output, I don't see anything else using the UART. The only
> output I see on the console at that time is coming from linux kernel.
> 
> Would you recommend any additional check?

I have no experience in the driver, I should avoid any noise. But two
things in my head for quick trying.

- First, you could try earlycon mode, e.g., add option in kernel
  command line:
  
    earlycon=pl011,mmio32,0xc280000
    earlycon=pl011,0xc280000

  This would be possible to give more printing logs. If earlycon works
  well, then the issue might be caused by later init code (clock, or
  UART driver itself).

- Try another UART port if this is possible.

Just curious, you mentioned you are working on the mainline kernel. If
you can confirm a workable kernel version, then this info can help to
rule out hardware issue and we can review the delta changes.

Thanks,
Leo