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Date: Tue, 16 Apr 2024 19:15:03 +0000
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
From: Michael Pratt <mcpratt@pm.me>
Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Jiri Slaby <jirislaby@kernel.org>, Wander Lairson Costa <wander@redhat.com>, =?utf-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>, Vamshi Gajjela <vamshigajjela@google.com>
Subject: Re: [PATCH v2 3/3] serial: 8250: Set fifo timeout using uart_fifo_timeout()
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Hi Andy,

On Tuesday, April 16th, 2024 at 14:57, Andy Shevchenko <andriy.shevchenko@l=
inux.intel.com> wrote:

>=20
> > unsigned int status, tmout =3D 10000;
> >=20
> > - /* Wait up to 10ms for the character(s) to be sent. /
> > + / Wait for a time relative to buffer size and baud */
> > + if (up->fifo_enable && up->port.timeout)
> > + tmout =3D jiffies_to_usecs(up->port.timeout);
>=20
>=20
> Why do we still use that default? Can't we calculate timeout even for\
> FIFO-less / FIFO-disabled devices?

Maybe it's possible that there is some kind of rare case where the LSR regi=
ster
is not working or not configured properly for a device in which support
is being worked on...without a timeout, that would result in an infinite lo=
op.

AFAIK, when everything is working properly, there is no such thing as needi=
ng
a timeout for a uart device without fifo, as every single byte written woul=
d trigger
an interrupt anyway.

> --
> With Best Regards,
> Andy Shevchenko

--
MCP