[src/trunk]: src/sys/dev/usb The second REQ_RESET USB request by reset_chip()...

[nisimura <nisimura%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f3916fbbfe40
branches:  trunk
changeset: 1022355:f3916fbbfe40
user:      nisimura <nisimura%NetBSD.org@localhost>
date:      Wed Jul 14 07:34:16 2021 +0000

description:
The second REQ_RESET USB request by reset_chip() makes LCR, PRE and DIV
registers to have default values 8N1 and 19200 just as the first req does.
Nuke reset_chip() and rundandant set_dte_rate() to amend.
While here added some narrative about prescale/divisor calculation.

diffstat:

 sys/dev/usb/uchcom.c |  60 +++++++++++++++++++++++----------------------------
 1 files changed, 27 insertions(+), 33 deletions(-)

diffs (120 lines):

diff -r b9888f92399d -r f3916fbbfe40 sys/dev/usb/uchcom.c
--- a/sys/dev/usb/uchcom.c      Wed Jul 14 07:24:14 2021 +0000
+++ b/sys/dev/usb/uchcom.c      Wed Jul 14 07:34:16 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uchcom.c,v 1.37 2021/04/24 23:36:59 thorpej Exp $      */
+/*     $NetBSD: uchcom.c,v 1.38 2021/07/14 07:34:16 nisimura Exp $     */
 
 /*
  * Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uchcom.c,v 1.37 2021/04/24 23:36:59 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uchcom.c,v 1.38 2021/07/14 07:34:16 nisimura Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_usb.h"
@@ -118,9 +118,6 @@
 #define UCHCOMIBUFSIZE 256
 #define UCHCOMOBUFSIZE 256
 
-#define UCHCOM_RESET_VALUE     0x501F
-#define UCHCOM_RESET_INDEX     0xD90A
-
 struct uchcom_softc
 {
        device_t                sc_dev;
@@ -155,6 +152,7 @@
        uint8_t         dv_div;
 };
 
+/* 0,1,2,3,7 are prescale factors for given 4x 12000000 clock formula */
 static const uint32_t rates4x[8] = {
        [0] = 4 * 12000000 / 1024,
        [1] = 4 * 12000000 / 128,
@@ -618,6 +616,24 @@
 static int
 calc_divider_settings(struct uchcom_divider *dp, uint32_t rate)
 {
+/*
+ * combined with rates4x[] defined above, this routine generates,
+ *   1200: prescale = 1/0x1, divisor = 178/0xb2
+ *   2400: prescale = 1/0x1, divisor = 217/0xd9
+ *   4800: prescale = 2/0x2, divisor = 100/0x64
+ *   9600: prescale = 2/0x2, divisor = 178/0xb2
+ *  19200: prescale = 2/0x2, divisor = 217/0xd9
+ *  38400: prescale = 3/0x3, divisor = 100/0x64
+ *  57600: prescale = 2/0x2, divisor = 243/0xf3
+ * 115200: prescale = 3/0x3, divisor = 204/0xcc
+ * 921600: prescale = 7/0x7, divisor = 243/0xf3
+ * 500000: prescale = 3/0x3, divisor = 244/0xf4
+ * 1000000: prescale = 3/0x3, divisor = 250/0xfa
+ * 1500000: prescale = 3/0x3, divisor = 252/0xfc
+ * 2000000: prescale = 3/0x3, divisor = 253/0xfd
+ * 2500000: unsupported
+ * 3000000: prescale = 3/0x3, divisor = 254/0xfe
+ */
        size_t i;
        uint32_t best, div, pre;
        const uint32_t rate4x = rate * 4U;
@@ -652,7 +668,7 @@
                return -1;
 
        dp->dv_prescaler = pre;
-       dp->dv_div = (uint8_t)-div;
+       dp->dv_div = 256 - div;
 
        return 0;
 }
@@ -740,29 +756,15 @@
                    usbd_errstr(err));
                return EIO;
        }
-
+       /*
+        * this REQ_RESET call ends up with
+        * LCR=0xc0 (8N1)
+        * PRE=0x02, DIV=0xb2 (19200)
+        */
        return 0;
 }
 
 static int
-reset_chip(struct uchcom_softc *sc)
-{
-       usbd_status err;
-
-       err = generic_control_out(sc, UCHCOM_REQ_RESET,
-           UCHCOM_RESET_VALUE, UCHCOM_RESET_INDEX);
-       if (err)
-               goto failed;
-
-       return 0;
-
-failed:
-       printf("%s: cannot reset: %s\n",
-              device_xname(sc->sc_dev), usbd_errstr(err));
-       return EIO;
-}
-
-static int
 setup_comm(struct uchcom_softc *sc)
 {
        int ret;
@@ -787,14 +789,6 @@
        if (ret)
                return ret;
 
-       ret = reset_chip(sc);
-       if (ret)
-               return ret;
-
-       ret = set_dte_rate(sc, TTYDEF_SPEED); /* XXX */
-       if (ret)
-               return ret;
-
        sc->sc_dtr = sc->sc_rts = 1;
        ret = set_dtrrts(sc, sc->sc_dtr, sc->sc_rts);
        if (ret)