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Date:   Thu, 14 Dec 2023 14:19:44 +0000
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Tudor Ambarus" <tudor.ambarus@linaro.org>,
        "Peter Griffin" <peter.griffin@linaro.org>,
        "Rob Herring" <robh+dt@kernel.org>,
        krzysztof.kozlowski+dt@linaro.org,
        "Michael Turquette" <mturquette@baylibre.com>,
        "Stephen Boyd" <sboyd@kernel.org>,
        "Conor Dooley" <conor+dt@kernel.org>, andi.shyti@kernel.org,
        "Alim Akhtar" <alim.akhtar@samsung.com>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        "Jiri Slaby" <jirislaby@kernel.org>,
        "Catalin Marinas" <catalin.marinas@arm.com>,
        "Will Deacon" <will@kernel.org>,
        "Sylwester Nawrocki" <s.nawrocki@samsung.com>,
        "Tomasz Figa" <tomasz.figa@gmail.com>,
        "Chanwoo Choi" <cw00.choi@samsung.com>,
        "Sam Protsenko" <semen.protsenko@linaro.org>
Cc:     =?UTF-8?Q?Andr=C3=A9_Draszik?= <andre.draszik@linaro.org>,
        saravanak@google.com, "William McVicker" <willmcvicker@google.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-clk@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-i2c@vger.kernel.org, linux-serial@vger.kernel.org
Subject: Re: [PATCH 05/13] tty: serial: samsung: add gs101 earlycon support
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On Thu, Dec 14, 2023, at 13:52, Tudor Ambarus wrote:
> On 12/14/23 12:01, Arnd Bergmann wrote:
>> On Thu, Dec 14, 2023, at 11:52, Tudor Ambarus wrote:
>>> +static int __init gs101_early_console_setup(struct earlycon_device *device,
>> 
>
> It works if in device tree one specifies the reg-io-width property and
> sets it to 4. If the reg-io-width is not specified, the iotype defaults
> to UPIO_MEM causing the SError interrupt on gs101 which makes the system
> unusable.

In the case of incorrect DT data like a missing reg-io-width property,
I would expect it to still fail once the regular console or tty takes
over from earlycon.

> Also, if the earlycon comes specified from the kernel params, the
> of_setup_earlycon() is no longer called and the earlycon will be set
> solely based on the kernel params buffer, thus allowing users to crash
> the kernel on wrong earlycon definitions.

But that in turn is the same as specifying any other incorrect earlycon.

> If you think the change is fine, I can amend the commit message with the
> description from above.

I'm still not convinced we need a special case here when everything else
just requires passing the correct data.

     Arnd