linux-kernel - Re: [PATCH v1 RESEND] serial: 8250: Set fifo timeout with uart_fifo

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Date: Thu, 11 Jan 2024 07:52:37 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Michael Pratt <mcpratt@...me>
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Jiri Slaby <jirislaby@...nel.org>,
	Wander Lairson Costa <wander@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v1 RESEND] serial: 8250: Set fifo timeout with
 uart_fifo_timeout()

On Thu, Jan 11, 2024 at 12:27:07AM +0000, Michael Pratt wrote:
> Commit 8f3631f0f6eb ("serial/8250: Use fifo in 8250 console driver")
> reworked functions for basic 8250 and 16550 type serial devices
> in order to enable and use the internal FIFO device for buffering,
> however the default timeout of 10 ms remained, which is proving
> to be insufficient for low baud rates like 9600, causing data overrun.
> 
> Unforunately, that commit was written and accepted just before commit
> 31f6bd7fad3b ("serial: Store character timing information to uart_port")
> which introduced the frame_time member of the uart_port struct
> in order to store the amount of time it takes to send one UART frame
> relative to the baud rate and other serial port configuration,
> and commit f9008285bb69 ("serial: Drop timeout from uart_port")
> which established function uart_fifo_timeout() in order to
> calculate a reasonable timeout to wait for all frames
> in the FIFO device to flush before writing data again
> using the now stored frame_time value and size of the buffer.
> 
> Fix this by using the new function to calculate the timeout
> whenever the buffer is larger than 1 byte (unknown port default).
> 
> Tested on a MIPS device (ar934x) at baud rates 625, 9600, 115200.
> 
> Signed-off-by: Michael Pratt <mcpratt@...me>
> ---
> v1 thread: https://lore.kernel.org/linux-serial/20231125063552.517-1-mcpratt@pm.me/

What commit id does this fix?

thanks,

greg k-h