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Message-ID: <ca6b70a2-9bcc-fb86-200c-e1714c9d53be@baylibre.com>
Date:   Fri, 6 May 2022 09:55:05 +0200
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Subject: Re: [PATCH printk v5 1/1] printk: extend console_lock for per-console
 locking
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To:     Marek Szyprowski <m.szyprowski@samsung.com>,
        John Ogness <john.ogness@linutronix.de>,
        Petr Mladek <pmladek@suse.com>
Cc:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-amlogic@lists.infradead.org
References: <Ymfgis0EAw0Oxoa5@alley> <Ymfwk+X0CHq6ex3s@alley>
 <CGME20220427070833eucas1p27a32ce7c41c0da26f05bd52155f0031c@eucas1p2.samsung.com>
 <2a82eae7-a256-f70c-fd82-4e510750906e@samsung.com> <Ymjy3rHRenba7r7R@alley>
 <b6c1a8ac-c691-a84d-d3a1-f99984d32f06@samsung.com>
 <87fslyv6y3.fsf@jogness.linutronix.de>
 <51dfc4a0-f6cf-092f-109f-a04eeb240655@samsung.com>
 <87k0b6blz2.fsf@jogness.linutronix.de>
 <32bba8f8-dec7-78aa-f2e5-f62928412eda@samsung.com> <Ym/Z7PYPqvWPEjuL@alley>
 <45849b63-d7a8-5cc3-26ad-256a28d09991@samsung.com>
 <87pmktm2a9.fsf@jogness.linutronix.de> <87a6bwapij.fsf@jogness.linutronix.de>
 <87zgjvd2zb.fsf@jogness.linutronix.de>
 <b7c81f02-039e-e877-d7c3-6834728d2117@samsung.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
In-Reply-To: <b7c81f02-039e-e877-d7c3-6834728d2117@samsung.com>
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Hi,

On 06/05/2022 08:43, Marek Szyprowski wrote:
> Hi John,
> 
> On 06.05.2022 00:33, John Ogness wrote:
>> On 2022-05-05, John Ogness <john.ogness@linutronix.de> wrote:
>>> I will go through and check if all access to AML_UART_CONTROL is
>>> protected by port->lock.
>> The startup() callback of the uart_ops is not called with the port
>> locked. I'm having difficulties identifying if the startup() callback
>> can occur after the console was already registered via meson_uart_init()
>> and could be actively printing, but I see other serial drivers are
>> protecting their registers in the startup() callback with the
>> port->lock.
>>
>> Could you try booting the meson hardware with the following change? (And
>> removing any previous debug changes I posted?)
> 
> Bingo! It looks that the startup() is called when getty initializes
> console. This fixed the issues observed on the Amlogic Meson based boards.
> 
> Feel free to add:
> 
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> 
> Best regards

Thanks all for figuring out the issue, perhaps other uart drivers could fall
in the same issue if startup code isn't protected with lock ?

Neil