linux-kernel - Re: [PATCH tty-next v3 1/6] serial: 8250: Adjust the timeout for FIFO mode

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Message-ID: <841pyqavhc.fsf@jogness.linutronix.de>
Date: Mon, 02 Dec 2024 17:47:03 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Jiri Slaby <jirislaby@...nel.org>, "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Petr Mladek
 <pmladek@...e.com>, Sergey Senozhatsky <senozhatsky@...omium.org>, Steven
 Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de>, Esben
 Haabendal <esben@...nix.com>, linux-serial@...r.kernel.org,
 linux-kernel@...r.kernel.org, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, Rengarajan S
 <rengarajan.s@...rochip.com>, Jeff Johnson <quic_jjohnson@...cinc.com>,
 Serge Semin <fancer.lancer@...il.com>, Lino Sanfilippo
 <l.sanfilippo@...bus.com>, Wander Lairson Costa <wander@...hat.com>
Subject: Re: [PATCH tty-next v3 1/6] serial: 8250: Adjust the timeout for
 FIFO mode

On 2024-12-02, Jiri Slaby <jirislaby@...nel.org> wrote:
> I am still asking why do you want to wait for the TX machinery at the
> *end* (for the last 64 B of the 640 B line) of transmission at all? It
> occurs to me as wasted cycles.

The printk-framework has always expected that when console->write()
returns, the data has been flushed out of the hardware. I am guessing
because it is easiest to avoid possible data loss, for example, due to
suspending hardware.

If you want me to change the current behavior, I can do that in a
separate patch. I would like this patch to only be about fixing the FIFO
timeout issue.

John