From: Max Staudt <mstaudt@suse.de>
To: gregkh@linuxfoundation.org
Cc: mstaudt@suse.de, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCHv2] 8250: option 'force_polling' for buggy IRQs
Date: Tue, 26 Jul 2016 13:47:31 +0200 [thread overview]
Message-ID: <1469533651-23384-1-git-send-email-mstaudt@suse.de> (raw)
In-Reply-To: <201607260241.cWzeZvYH%fengguang.wu@intel.com>
Some serial ports may not emit IRQs properly, or there may be a defect
in their routing on the motherboard.
This patch allows these ports to be used anyway (or until a better
workaround is known for a specific platform), though with no guarantees.
If you have such a buggy UART, boot Linux with 8250.force_polling=1 .
It is essentially the kernel level version of:
setserial /dev/ttySn irq 0
and builds upon the polling code that is already in the kernel.
---
v2:
- Fixed module_param_cb() line
---
drivers/tty/serial/8250/8250_core.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 13ad5c3..536e226 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -58,6 +58,11 @@ static struct uart_driver serial8250_reg;
static unsigned int skip_txen_test; /* force skip of txen test at init time */
+/* Force polled mode for all newly detected ports.
+ * This can be used if IRQs don't arrive and similar buggyness.
+ */
+static unsigned int force_polling;
+
#define PASS_LIMIT 512
#include <asm/serial.h>
@@ -335,6 +340,13 @@ static int univ8250_setup_irq(struct uart_8250_port *up)
uart_poll_timeout(port) + HZ / 5);
}
+ if (force_polling) {
+ pr_debug("ttyS%d - using polled mode instead of interrupt %u\n",
+ serial_index(port),
+ port->irq);
+ port->irq = 0;
+ }
+
/*
* If the "interrupt" for this port doesn't correspond with any
* hardware interrupt, we use a timer-based system. The original
@@ -1206,6 +1218,9 @@ MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STR
module_param(skip_txen_test, uint, 0644);
MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time");
+module_param(force_polling, uint, 0644);
+MODULE_PARM_DESC(force_polling, "Set ports to polling mode at init time");
+
#ifdef CONFIG_SERIAL_8250_RSA
module_param_array(probe_rsa, ulong, &probe_rsa_count, 0444);
MODULE_PARM_DESC(probe_rsa, "Probe I/O ports for RSA");
@@ -1232,6 +1247,7 @@ static void __used s8250_options(void)
module_param_cb(share_irqs, ¶m_ops_uint, &share_irqs, 0644);
module_param_cb(nr_uarts, ¶m_ops_uint, &nr_uarts, 0644);
module_param_cb(skip_txen_test, ¶m_ops_uint, &skip_txen_test, 0644);
+ module_param_cb(force_polling, ¶m_ops_uint, &force_polling, 0644);
#ifdef CONFIG_SERIAL_8250_RSA
__module_param_call(MODULE_PARAM_PREFIX, probe_rsa,
¶m_array_ops, .arr = &__param_arr_probe_rsa,
--
2.6.6
next prev parent reply other threads:[~2016-07-26 11:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-25 17:36 [PATCH] 8250: option 'force_polling' for buggy IRQs Max Staudt
2016-07-25 17:47 ` Greg KH
2016-07-26 11:42 ` Max Staudt
2016-07-26 15:08 ` Greg KH
2016-07-26 16:18 ` Max Staudt
2016-07-27 12:09 ` One Thousand Gnomes
2016-07-27 12:14 ` Max Staudt
2016-07-27 13:33 ` Theodore Ts'o
2016-07-27 20:01 ` One Thousand Gnomes
2016-07-28 9:59 ` Max Staudt
2016-07-28 14:47 ` Greg KH
2016-07-28 16:01 ` Theodore Ts'o
2016-07-28 18:40 ` Eric W. Biederman
2016-07-29 9:23 ` One Thousand Gnomes
2016-07-29 9:58 ` Max Staudt
2016-07-29 17:38 ` Eric W. Biederman
2016-08-01 15:27 ` One Thousand Gnomes
2016-07-25 18:19 ` kbuild test robot
2016-07-26 11:47 ` Max Staudt [this message]
2016-07-26 11:54 ` [PATCHv3] " Max Staudt
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