linux-kernel - Re: [PATCH tty-next v3 2/6] serial: 8250: Use high-level write function for FIFO

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Message-ID: <ZxuiMdrGcsuPp8OG@smile.fi.intel.com>
Date: Fri, 25 Oct 2024 16:50:41 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.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,
	Rengarajan S <rengarajan.s@...rochip.com>,
	Serge Semin <fancer.lancer@...il.com>,
	Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH tty-next v3 2/6] serial: 8250: Use high-level write
 function for FIFO

On Fri, Oct 25, 2024 at 01:03:24PM +0206, John Ogness wrote:
> Currently serial8250_console_fifo_write() directly writes into the
> UART_TX register, rather than using the high-level function
> serial8250_console_putchar(). This is because
> serial8250_console_putchar() waits for the holding register to
> become empty. That would defeat the purpose of the FIFO code.

You can slightly reformat the above to make it less shaky in terms
of the efficiency of a line capacity usage.

Currently serial8250_console_fifo_write() directly writes into
the UART_TX register, rather than using the high-level function
serial8250_console_putchar(). This is because
serial8250_console_putchar() waits for the holding register
to become empty. That would defeat the purpose of the FIFO code.

> Move the LSR_THRE waiting to a new function
> serial8250_console_wait_putchar() so that the FIFO code can use
> serial8250_console_putchar(). This will be particularly important
> for a follow-up commit, where output bytes are inspected to track
> newlines.

> This is only refactoring and has no functional change.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko