linux-serial.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Tomasz Moń" <tomasz.mon@camlingroup.com>
To: linux-serial@vger.kernel.org
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Jiri Slaby" <jirislaby@kernel.org>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabio Estevam" <festevam@gmail.com>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	k.drobinski@camlintechnologies.com,
	"Tomasz Moń" <tomasz.mon@camlingroup.com>
Subject: [PATCH] serial: imx: reduce RX interrupt frequency
Date: Tue,  4 Jan 2022 11:32:03 +0100	[thread overview]
Message-ID: <20220104103203.2033673-1-tomasz.mon@camlingroup.com> (raw)

Triggering RX interrupt for every byte defeats the purpose of aging
timer and leads to interrupt starvation at high baud rates.

Increase receiver trigger level to 8 to increase the minimum period
between RX interrupts to 8 characters time. The tradeoff is increased
latency. In the worst case scenario, where RX data has intercharacter
delay slightly less than aging timer (8 characters time), it can take
up to 63 characters time for the interrupt to be raised since the
reception of the first character.

Signed-off-by: Tomasz Moń <tomasz.mon@camlingroup.com>
---
 drivers/tty/serial/imx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 90f82e6c54e4..3c812c47ecc0 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1255,7 +1255,7 @@ static void imx_uart_clear_rx_errors(struct imx_port *sport)
 }
 
 #define TXTL_DEFAULT 2 /* reset default */
-#define RXTL_DEFAULT 1 /* reset default */
+#define RXTL_DEFAULT 8 /* 8 characters or aging timer */
 #define TXTL_DMA 8 /* DMA burst setting */
 #define RXTL_DMA 9 /* DMA burst setting */
 
-- 
2.25.1


             reply	other threads:[~2022-01-04 10:44 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-04 10:32 Tomasz Moń [this message]
2022-01-04 10:43 ` [PATCH] serial: imx: reduce RX interrupt frequency Ahmad Fatoum
2022-01-04 11:05   ` Tomasz Moń
2022-01-04 10:54 ` Greg Kroah-Hartman
2022-01-04 11:13   ` Tomasz Moń
2022-01-04 11:38     ` Greg Kroah-Hartman
2022-01-04 22:49       ` Uwe Kleine-König
2022-01-05  7:59         ` Tomasz Moń
2022-01-05 10:37           ` Greg Kroah-Hartman
2022-01-05 10:56             ` Tomasz Moń
2022-01-05 10:57             ` Marc Kleine-Budde
2022-01-06 15:39               ` Sergey Organov
2022-01-05 13:34         ` Sergey Organov
2022-01-06 15:05           ` Uwe Kleine-König
2022-01-10  6:14             ` Tomasz Moń
2022-01-10  8:31               ` Uwe Kleine-König
2022-01-05 13:00   ` Sergey Organov
2022-01-05 13:04     ` Marc Kleine-Budde
2022-01-05 13:37       ` Sergey Organov
2022-01-05 13:40         ` Marc Kleine-Budde
2022-01-05 14:37           ` Sergey Organov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20220104103203.2033673-1-tomasz.mon@camlingroup.com \
    --to=tomasz.mon@camlingroup.com \
    --cc=festevam@gmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jirislaby@kernel.org \
    --cc=k.drobinski@camlintechnologies.com \
    --cc=kernel@pengutronix.de \
    --cc=linux-imx@nxp.com \
    --cc=linux-serial@vger.kernel.org \
    --cc=s.hauer@pengutronix.de \
    --cc=shawnguo@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).