linux-kernel - [PATCH v2 2/3] serial: 8250: Store whether fifo device is enabled

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Date: Tue, 16 Apr 2024 18:29:56 +0000
From: Michael Pratt <mcpratt@...me>
To: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>
Cc: Wander Lairson Costa <wander@...hat.com>, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Vamshi Gajjela <vamshigajjela@...gle.com>, Michael Pratt <mcpratt@...me>
Subject: [PATCH v2 2/3] serial: 8250: Store whether fifo device is enabled

Currently, there are 7 checks for whether to enable
the internal fifo device of a 8250/16550 type uart.

Instead of checking all 7 values again whenever
we need to know whether we have the fifo device enabled,
store the result as a struct member of uart_8250_port.

This can, for example, lessen the amount
of calculations done during a write operation.

Signed-off-by: Michael Pratt <mcpratt@...me>
---
V1 -> V2: new commit

 drivers/tty/serial/8250/8250_port.c | 2 ++
 include/linux/serial_8250.h         | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index fc9dd5d45295..5b0cfe6bc98c 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -3392,6 +3392,8 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
 		 */
 		!(up->port.flags & UPF_CONS_FLOW);
 
+	up->fifo_enable = use_fifo;
+
 	if (likely(use_fifo))
 		serial8250_console_fifo_write(up, s, count);
 	else
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index fd59ed2cca53..017429f0e743 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -127,6 +127,7 @@ struct uart_8250_port {
 	struct list_head	list;		/* ports on this IRQ */
 	u32			capabilities;	/* port capabilities */
 	u16			bugs;		/* port bugs */
+	unsigned int		fifo_enable;	/* fifo enabled if capable */
 	unsigned int		tx_loadsz;	/* transmit fifo load size */
 	unsigned char		acr;
 	unsigned char		fcr;
-- 
2.30.2