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From: Marcel Moolenaar <marcel@FreeBSD.org>
Date: Thu, 26 May 2011 17:02:56 +0000 (UTC)
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Subject: svn commit: r222317 - head/sys/dev/uart
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Author: marcel
Date: Thu May 26 17:02:56 2011
New Revision: 222317
URL: http://svn.freebsd.org/changeset/base/222317

Log:
  Ignore MCR[6] during the probe to fix a false negative. Bit 6 of the
  MCR register on the Sunix Sun1699 chip tends to be set but doesn't
  seem to have a function. That is, FreeBSD just works (provided the
  correct RCLK is used) regardless.
  
  PR:		kern/129663
  Diagnostics:	Eygene Ryabinkin <rea-fbsd at codelabs.ru>
  MFC after:	3 days

Modified:
  head/sys/dev/uart/uart_dev_ns8250.c

Modified: head/sys/dev/uart/uart_dev_ns8250.c
==============================================================================
--- head/sys/dev/uart/uart_dev_ns8250.c	Thu May 26 16:59:42 2011	(r222316)
+++ head/sys/dev/uart/uart_dev_ns8250.c	Thu May 26 17:02:56 2011	(r222317)
@@ -242,8 +242,14 @@ ns8250_probe(struct uart_bas *bas)
 	val = uart_getreg(bas, REG_IIR);
 	if (val & 0x30)
 		return (ENXIO);
+	/*
+	 * Bit 6 of the MCR (= 0x40) appears to be 1 for the Sun1699
+	 * chip, but otherwise doesn't seem to have a function. In
+	 * other words, uart(4) works regardless. Ignore that bit so
+	 * the probe succeeds.
+	 */
 	val = uart_getreg(bas, REG_MCR);
-	if (val & 0xe0)
+	if (val & 0xa0)
 		return (ENXIO);
 
 	return (0);