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List: xen-cvs
Subject: [Xen-changelog] [xen master] ns16550: delay resume until dom0 ACPI has a chance to run
From: patchbot () xen ! org
Date: 2013-04-24 18:55:02
Message-ID: E1UV4qM-0007iW-Ph () xenbits ! xen ! org
[Download RAW message or body]
commit 6e96c186d23873597896051b043cfeb119c4a7d5
Author: Ben Guthro <benjamin.guthro@citrix.com>
AuthorDate: Wed Apr 24 11:41:53 2013 +0200
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Wed Apr 24 11:41:53 2013 +0200
ns16550: delay resume until dom0 ACPI has a chance to run
Check for ioport access, before fully resuming operation, to avoid
spinning in __ns16550_poll when reading the LSR register returns 0xFF
on failing ioport access.
On some systems (like Lenovo T410, and some HP machines of similar vintage)
there is a SuperIO card that provides this legacy ioport on the LPC bus.
In this case, we need to wait for dom0's ACPI processing to run the proper
AML to re-initialize the chip, before we can use the card again.
This may cause a small amount of garbage to be written to the serial log
while we wait patiently for that AML to be executed.
This implementation limits the number of retries, to avoid a situation
where we keep trying over and over again, in the case of some other failure
on the ioport.
Signed-Off-By: Ben Guthro <benjamin.guthro@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
---
xen/drivers/char/ns16550.c | 55 +++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 54 insertions(+), 1 deletions(-)
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index a91743e..e0c87bb 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -45,6 +45,7 @@ static struct ns16550 {
struct irqaction irqaction;
/* UART with no IRQ line: periodically-polled I/O. */
struct timer timer;
+ struct timer resume_timer;
unsigned int timeout_ms;
bool_t intr_works;
/* PCI card parameters. */
@@ -123,6 +124,10 @@ static struct ns16550 {
/* Frequency of external clock source. This definition assumes PC platform. */
#define UART_CLOCK_HZ 1843200
+/* Resume retry settings */
+#define RESUME_DELAY MILLISECS(10)
+#define RESUME_RETRIES 100
+
static char ns_read_reg(struct ns16550 *uart, int reg)
{
if ( uart->remapped_io_base == NULL )
@@ -351,7 +356,7 @@ static void ns16550_suspend(struct serial_port *port)
uart->ps_bdf[2], PCI_COMMAND);
}
-static void ns16550_resume(struct serial_port *port)
+static void _ns16550_resume(struct serial_port *port)
{
struct ns16550 *uart = port->uart;
@@ -367,6 +372,54 @@ static void ns16550_resume(struct serial_port *port)
ns16550_setup_postirq(port->uart);
}
+static int ns16550_ioport_invalid(struct ns16550 *uart)
+{
+ return ((((unsigned char)ns_read_reg(uart, LSR)) == 0xff) &&
+ (((unsigned char)ns_read_reg(uart, MCR)) == 0xff) &&
+ (((unsigned char)ns_read_reg(uart, IER)) == 0xff) &&
+ (((unsigned char)ns_read_reg(uart, IIR)) == 0xff) &&
+ (((unsigned char)ns_read_reg(uart, LCR)) == 0xff));
+}
+
+static int delayed_resume_tries;
+static void ns16550_delayed_resume(void *data)
+{
+ struct serial_port *port = data;
+ struct ns16550 *uart = port->uart;
+
+ if ( ns16550_ioport_invalid(port->uart) && delayed_resume_tries-- )
+ set_timer(&uart->resume_timer, NOW() + RESUME_DELAY);
+ else
+ _ns16550_resume(port);
+}
+
+static void ns16550_resume(struct serial_port *port)
+{
+ struct ns16550 *uart = port->uart;
+
+ /*
+ * Check for ioport access, before fully resuming operation.
+ * On some systems, there is a SuperIO card that provides
+ * this legacy ioport on the LPC bus.
+ *
+ * We need to wait for dom0's ACPI processing to run the proper
+ * AML to re-initialize the chip, before we can use the card again.
+ *
+ * This may cause a small amount of garbage to be written
+ * to the serial log while we wait patiently for that AML to
+ * be executed. However, this is preferable to spinning in an
+ * infinite loop, as seen on a Lenovo T430, when serial was enabled.
+ */
+ if ( ns16550_ioport_invalid(uart) )
+ {
+ delayed_resume_tries = RESUME_RETRIES;
+ init_timer(&uart->resume_timer, ns16550_delayed_resume, port, 0);
+ set_timer(&uart->resume_timer, NOW() + RESUME_DELAY);
+ }
+ else
+ _ns16550_resume(port);
+}
+
#ifdef CONFIG_X86
static void __init ns16550_endboot(struct serial_port *port)
{
--
generated by git-patchbot for /home/xen/git/xen.git#master
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