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Calculate uchcom(4) dividers differently; usually the same, but sometimes better.

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This commit is contained in:
jakllsch 2018-12-13 01:40:02 +00:00
parent daf842171c
commit 2bd6662aa4
1 changed files with 39 additions and 44 deletions
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83
sys/dev/usb/uchcom.c
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@ -1,4 +1,4 @@
/* $NetBSD: uchcom.c,v 1.26 2018/12/13 00:36:30 jakllsch Exp $ */
/* $NetBSD: uchcom.c,v 1.27 2018/12/13 01:40:02 jakllsch Exp $ */
/*
* Copyright (c) 2007 The NetBSD Foundation, Inc.
@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uchcom.c,v 1.26 2018/12/13 00:36:30 jakllsch Exp $");
__KERNEL_RCSID(0, "$NetBSD: uchcom.c,v 1.27 2018/12/13 01:40:02 jakllsch Exp $");
#ifdef _KERNEL_OPT
#include "opt_usb.h"
@ -91,8 +91,6 @@ int uchcomdebug = 0;
#define UCHCOM_VER_20 0x20
#define UCHCOM_VER_30 0x30
#define UCHCOM_BASE_UNKNOWN 0
#define UCHCOM_BPS_PRE_IMM 0x80 /* CH341: immediate RX forwarding */
#define UCHCOM_DTR_MASK 0x20
@ -154,25 +152,14 @@ struct uchcom_divider
uint8_t dv_div;
};
struct uchcom_divider_record
{
uint32_t dvr_high;
uint32_t dvr_low;
uint32_t dvr_base_clock;
struct uchcom_divider dvr_divider;
static const uint32_t rates4x[8] = {
[0] = 4 * 12000000 / 1024,
[1] = 4 * 12000000 / 128,
[2] = 4 * 12000000 / 16,
[3] = 4 * 12000000 / 2,
[7] = 4 * 12000000,
};
static const struct uchcom_divider_record dividers[] =
{
{ 307200, 307200, UCHCOM_BASE_UNKNOWN, { 7, 0xD9 } },
{ 921600, 921600, UCHCOM_BASE_UNKNOWN, { 7, 0xF3 } },
{ 2999999, 23530, 6000000, { 3, 0 } },
{ 23529, 2942, 750000, { 2, 0 } },
{ 2941, 368, 93750, { 1, 0 } },
{ 367, 1, 11719, { 0, 0 } },
};
#define NUM_DIVIDERS (sizeof (dividers) / sizeof (dividers[0]))
static const struct usb_devno uchcom_devs[] = {
{ USB_VENDOR_QINHENG2, USB_PRODUCT_QINHENG2_CH341SER },
{ USB_VENDOR_QINHENG, USB_PRODUCT_QINHENG_CH340 },
@ -646,33 +633,41 @@ set_break(struct uchcom_softc *sc, int onoff)
static int
calc_divider_settings(struct uchcom_divider *dp, uint32_t rate)
{
int i;
const struct uchcom_divider_record *rp;
uint32_t div, rem;
size_t i;
uint32_t best, div, pre;
const uint32_t rate4x = rate * 4U;
/* find record */
for (i=0; i<NUM_DIVIDERS; i++) {
if (dividers[i].dvr_high >= rate &&
dividers[i].dvr_low <= rate) {
rp = &dividers[i];
goto found;
if (rate == 0 || rate > 3000000)
return -1;
pre = __arraycount(rates4x);
best = UINT32_MAX;
for (i = 0; i < __arraycount(rates4x); i++) {
uint32_t score, try;
try = rates4x[i] * 2 / rate4x;
try = (try / 2) + (try & 1);
if (try < 2)
continue;
if (try > 255)
try = 255;
score = abs((int)rate4x - rates4x[i] / try);
if (score < best) {
best = score;
pre = i;
div = try;
}
}
return -1;
found:
dp->dv_prescaler = rp->dvr_divider.dv_prescaler;
if (rp->dvr_base_clock == UCHCOM_BASE_UNKNOWN)
dp->dv_div = rp->dvr_divider.dv_div;
else {
div = rp->dvr_base_clock / rate;
rem = rp->dvr_base_clock % rate;
if (div==0 || div>=0xFF)
return -1;
if ((rem<<1) >= rate)
div += 1;
dp->dv_div = (uint8_t)-div;
}
if (pre >= __arraycount(rates4x))
return -1;
if ((rates4x[pre] / div / 4) < (rate * 99 / 100))
return -1;
if ((rates4x[pre] / div / 4) > (rate * 101 / 100))
return -1;
dp->dv_prescaler = pre;
dp->dv_div = (uint8_t)-div;
return 0;
}