svn commit: r355572 - in head: share/man/man4 sys/dev/usb/serial

[Ian Lepore]

Author: ian
Date: Mon Dec  9 21:55:44 2019
New Revision: 355572
URL: https://svnweb.freebsd.org/changeset/base/355572

Log:
  Allow baud rates of 1,228,800 and 1,843,200 on CP2101/2/3 usb-serial adapters.
  
  The datasheets for these chips claim the maximum is 921,600, but testing
  shows these two higher rates also work (but no rates above 921,600 other
  than these two work; these represent dividing the base buad clock by 3 and 2
  respectively).

Modified:
  head/share/man/man4/uslcom.4
  head/sys/dev/usb/serial/uslcom.c

Modified: head/share/man/man4/uslcom.4
==============================================================================
--- head/share/man/man4/uslcom.4	Mon Dec  9 21:10:18 2019	(r355571)
+++ head/share/man/man4/uslcom.4	Mon Dec  9 21:55:44 2019	(r355572)
@@ -16,7 +16,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 26, 2017
+.Dd December 9, 2019
 .Dt USLCOM 4
 .Os
 .Sh NAME
@@ -43,6 +43,11 @@ The
 .Nm
 driver supports Silicon Laboratories CP2101/CP2102/CP2103/CP2104/CP2105
 based USB serial adapters.
+.Pp
+The datasheets for the CP2101/CP2102/CP2103 list the maximum
+supported baud rate as 921,600.
+Empirical testing has shown that the rates 1,228,800 and 1,843,200 also work,
+at least on some hardware, so the driver allows setting those rates.
 .Sh HARDWARE
 The following devices should work with the
 .Nm

Modified: head/sys/dev/usb/serial/uslcom.c
==============================================================================
--- head/sys/dev/usb/serial/uslcom.c	Mon Dec  9 21:10:18 2019	(r355571)
+++ head/sys/dev/usb/serial/uslcom.c	Mon Dec  9 21:55:44 2019	(r355572)
@@ -624,7 +624,11 @@ uslcom_pre_param(struct ucom_softc *ucom, struct termi
 	case USLCOM_PARTNUM_CP2102:
 	case USLCOM_PARTNUM_CP2103:
 	default:
-		maxspeed = 921600;
+		/*
+		 * Datasheet for cp2102 says 921600 max.  Testing shows that
+		 * 1228800 and 1843200 work fine.
+		 */
+		maxspeed = 1843200;
 		break;
 	}
 	if (t->c_ospeed <= 0 || t->c_ospeed > maxspeed)