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linux/drivers/usb/serial/ch341.c
Johan Hovold 7c3d02285a USB: serial: ch341: fix receiver regression 
While assumed not to make a difference, not using the factor-2 prescaler
makes the receiver more susceptible to errors.

Specifically, there have been reports of problems with devices that
cannot generate a 115200 rate with a smaller error than 2.1% (e.g.
117647 bps). But this can also be reproduced with a low-speed RS232
tranceiver at 115200 when the input rate matches the nominal rate.

So whenever possible, enable the factor-2 prescaler and halve the
divisor in order to use settings closer to that of the previous
algorithm.

Fixes: 3571456508 ("USB: serial: ch341: reimplement line-speed handling")
Cc: stable <stable@vger.kernel.org>	# 5.5
Reported-by: Jakub Nantl <jn@forever.cz>
Tested-by: Jakub Nantl <jn@forever.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
2020-02-10 10:10:35 +01:00

712 lines
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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
* Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
* Copyright 2009, Boris Hajduk <boris@hajduk.org>
*
* ch341.c implements a serial port driver for the Winchiphead CH341.
*
* The CH341 device can be used to implement an RS232 asynchronous
* serial port, an IEEE-1284 parallel printer port or a memory-like
* interface. In all cases the CH341 supports an I2C interface as well.
* This driver only supports the asynchronous serial interface.
*/
#include <linux/kernel.h>
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
#include <asm/unaligned.h>
#define DEFAULT_BAUD_RATE 9600
#define DEFAULT_TIMEOUT 1000
/* flags for IO-Bits */
#define CH341_BIT_RTS (1 << 6)
#define CH341_BIT_DTR (1 << 5)
/******************************/
/* interrupt pipe definitions */
/******************************/
/* always 4 interrupt bytes */
/* first irq byte normally 0x08 */
/* second irq byte base 0x7d + below */
/* third irq byte base 0x94 + below */
/* fourth irq byte normally 0xee */
/* second interrupt byte */
#define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
/* status returned in third interrupt answer byte, inverted in data
from irq */
#define CH341_BIT_CTS 0x01
#define CH341_BIT_DSR 0x02
#define CH341_BIT_RI 0x04
#define CH341_BIT_DCD 0x08
#define CH341_BITS_MODEM_STAT 0x0f /* all bits */
/* Break support - the information used to implement this was gleaned from
* the Net/FreeBSD uchcom.c driver by Takanori Watanabe. Domo arigato.
*/
#define CH341_REQ_READ_VERSION 0x5F
#define CH341_REQ_WRITE_REG 0x9A
#define CH341_REQ_READ_REG 0x95
#define CH341_REQ_SERIAL_INIT 0xA1
#define CH341_REQ_MODEM_CTRL 0xA4
#define CH341_REG_BREAK 0x05
#define CH341_REG_LCR 0x18
#define CH341_NBREAK_BITS 0x01
#define CH341_LCR_ENABLE_RX 0x80
#define CH341_LCR_ENABLE_TX 0x40
#define CH341_LCR_MARK_SPACE 0x20
#define CH341_LCR_PAR_EVEN 0x10
#define CH341_LCR_ENABLE_PAR 0x08
#define CH341_LCR_STOP_BITS_2 0x04
#define CH341_LCR_CS8 0x03
#define CH341_LCR_CS7 0x02
#define CH341_LCR_CS6 0x01
#define CH341_LCR_CS5 0x00
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x4348, 0x5523) },
{ USB_DEVICE(0x1a86, 0x7523) },
{ USB_DEVICE(0x1a86, 0x5523) },
{ },
};
MODULE_DEVICE_TABLE(usb, id_table);
struct ch341_private {
spinlock_t lock; /* access lock */
unsigned baud_rate; /* set baud rate */
u8 mcr;
u8 msr;
u8 lcr;
};
static void ch341_set_termios(struct tty_struct *tty,
struct usb_serial_port *port,
struct ktermios *old_termios);
static int ch341_control_out(struct usb_device *dev, u8 request,
u16 value, u16 index)
{
int r;
dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
request, value, index);
r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
value, index, NULL, 0, DEFAULT_TIMEOUT);
if (r < 0)
dev_err(&dev->dev, "failed to send control message: %d\n", r);
return r;
}
static int ch341_control_in(struct usb_device *dev,
u8 request, u16 value, u16 index,
char *buf, unsigned bufsize)
{
int r;
dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
request, value, index, bufsize);
r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
value, index, buf, bufsize, DEFAULT_TIMEOUT);
if (r < (int)bufsize) {
if (r >= 0) {
dev_err(&dev->dev,
"short control message received (%d < %u)\n",
r, bufsize);
r = -EIO;
}
dev_err(&dev->dev, "failed to receive control message: %d\n",
r);
return r;
}
return 0;
}
#define CH341_CLKRATE 48000000
#define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact)))
#define CH341_MIN_RATE(ps) (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
static const speed_t ch341_min_rates[] = {
CH341_MIN_RATE(0),
CH341_MIN_RATE(1),
CH341_MIN_RATE(2),
CH341_MIN_RATE(3),
};
/*
* The device line speed is given by the following equation:
*
* baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where
*
* 0 <= ps <= 3,
* 0 <= fact <= 1,
* 2 <= div <= 256 if fact = 0, or
* 9 <= div <= 256 if fact = 1
*/
static int ch341_get_divisor(speed_t speed)
{
unsigned int fact, div, clk_div;
int ps;
/*
* Clamp to supported range, this makes the (ps < 0) and (div < 2)
* sanity checks below redundant.
*/
speed = clamp(speed, 46U, 3000000U);
/*
* Start with highest possible base clock (fact = 1) that will give a
* divisor strictly less than 512.
*/
fact = 1;
for (ps = 3; ps >= 0; ps--) {
if (speed > ch341_min_rates[ps])
break;
}
if (ps < 0)
return -EINVAL;
/* Determine corresponding divisor, rounding down. */
clk_div = CH341_CLK_DIV(ps, fact);
div = CH341_CLKRATE / (clk_div * speed);
/* Halve base clock (fact = 0) if required. */
if (div < 9 || div > 255) {
div /= 2;
clk_div *= 2;
fact = 0;
}
if (div < 2)
return -EINVAL;
/*
* Pick next divisor if resulting rate is closer to the requested one,
* scale up to avoid rounding errors on low rates.
*/
if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >=
16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1)))
div++;
/*
* Prefer lower base clock (fact = 0) if even divisor.
*
* Note that this makes the receiver more tolerant to errors.
*/
if (fact == 1 && div % 2 == 0) {
div /= 2;
fact = 0;
}
return (0x100 - div) << 8 | fact << 2 | ps;
}
static int ch341_set_baudrate_lcr(struct usb_device *dev,
struct ch341_private *priv, u8 lcr)
{
int val;
int r;
if (!priv->baud_rate)
return -EINVAL;
val = ch341_get_divisor(priv->baud_rate);
if (val < 0)
return -EINVAL;
/*
* CH341A buffers data until a full endpoint-size packet (32 bytes)
* has been received unless bit 7 is set.
*/
val |= BIT(7);
r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x1312, val);
if (r)
return r;
r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, lcr);
if (r)
return r;
return r;
}
static int ch341_set_handshake(struct usb_device *dev, u8 control)
{
return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
}
static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
{
const unsigned int size = 2;
char *buffer;
int r;
unsigned long flags;
buffer = kmalloc(size, GFP_KERNEL);
if (!buffer)
return -ENOMEM;
r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
if (r < 0)
goto out;
spin_lock_irqsave(&priv->lock, flags);
priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
spin_unlock_irqrestore(&priv->lock, flags);
out: kfree(buffer);
return r;
}
/* -------------------------------------------------------------------------- */
static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
{
const unsigned int size = 2;
char *buffer;
int r;
buffer = kmalloc(size, GFP_KERNEL);
if (!buffer)
return -ENOMEM;
/* expect two bytes 0x27 0x00 */
r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
if (r < 0)
goto out;
dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);
r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
if (r < 0)
goto out;
r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
if (r < 0)
goto out;
r = ch341_set_handshake(dev, priv->mcr);
out: kfree(buffer);
return r;
}
static int ch341_port_probe(struct usb_serial_port *port)
{
struct ch341_private *priv;
int r;
priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
if (!priv)
return -ENOMEM;
spin_lock_init(&priv->lock);
priv->baud_rate = DEFAULT_BAUD_RATE;
/*
* Some CH340 devices appear unable to change the initial LCR
* settings, so set a sane 8N1 default.
*/
priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
r = ch341_configure(port->serial->dev, priv);
if (r < 0)
goto error;
usb_set_serial_port_data(port, priv);
return 0;
error: kfree(priv);
return r;
}
static int ch341_port_remove(struct usb_serial_port *port)
{
struct ch341_private *priv;
priv = usb_get_serial_port_data(port);
kfree(priv);
return 0;
}
static int ch341_carrier_raised(struct usb_serial_port *port)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
if (priv->msr & CH341_BIT_DCD)
return 1;
return 0;
}
static void ch341_dtr_rts(struct usb_serial_port *port, int on)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
unsigned long flags;
/* drop DTR and RTS */
spin_lock_irqsave(&priv->lock, flags);
if (on)
priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
else
priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
spin_unlock_irqrestore(&priv->lock, flags);
ch341_set_handshake(port->serial->dev, priv->mcr);
}
static void ch341_close(struct usb_serial_port *port)
{
usb_serial_generic_close(port);
usb_kill_urb(port->interrupt_in_urb);
}
/* open this device, set default parameters */
static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
int r;
if (tty)
ch341_set_termios(tty, port, NULL);
dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
if (r) {
dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
__func__, r);
return r;
}
r = ch341_get_status(port->serial->dev, priv);
if (r < 0) {
dev_err(&port->dev, "failed to read modem status: %d\n", r);
goto err_kill_interrupt_urb;
}
r = usb_serial_generic_open(tty, port);
if (r)
goto err_kill_interrupt_urb;
return 0;
err_kill_interrupt_urb:
usb_kill_urb(port->interrupt_in_urb);
return r;
}
/* Old_termios contains the original termios settings and
* tty->termios contains the new setting to be used.
*/
static void ch341_set_termios(struct tty_struct *tty,
struct usb_serial_port *port, struct ktermios *old_termios)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
unsigned baud_rate;
unsigned long flags;
u8 lcr;
int r;
/* redundant changes may cause the chip to lose bytes */
if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
return;
baud_rate = tty_get_baud_rate(tty);
lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
switch (C_CSIZE(tty)) {
case CS5:
lcr |= CH341_LCR_CS5;
break;
case CS6:
lcr |= CH341_LCR_CS6;
break;
case CS7:
lcr |= CH341_LCR_CS7;
break;
case CS8:
lcr |= CH341_LCR_CS8;
break;
}
if (C_PARENB(tty)) {
lcr |= CH341_LCR_ENABLE_PAR;
if (C_PARODD(tty) == 0)
lcr |= CH341_LCR_PAR_EVEN;
if (C_CMSPAR(tty))
lcr |= CH341_LCR_MARK_SPACE;
}
if (C_CSTOPB(tty))
lcr |= CH341_LCR_STOP_BITS_2;
if (baud_rate) {
priv->baud_rate = baud_rate;
r = ch341_set_baudrate_lcr(port->serial->dev, priv, lcr);
if (r < 0 && old_termios) {
priv->baud_rate = tty_termios_baud_rate(old_termios);
tty_termios_copy_hw(&tty->termios, old_termios);
} else if (r == 0) {
priv->lcr = lcr;
}
}
spin_lock_irqsave(&priv->lock, flags);
if (C_BAUD(tty) == B0)
priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
spin_unlock_irqrestore(&priv->lock, flags);
ch341_set_handshake(port->serial->dev, priv->mcr);
}
static void ch341_break_ctl(struct tty_struct *tty, int break_state)
{
const uint16_t ch341_break_reg =
((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
struct usb_serial_port *port = tty->driver_data;
int r;
uint16_t reg_contents;
uint8_t *break_reg;
break_reg = kmalloc(2, GFP_KERNEL);
if (!break_reg)
return;
r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
ch341_break_reg, 0, break_reg, 2);
if (r < 0) {
dev_err(&port->dev, "%s - USB control read error (%d)\n",
__func__, r);
goto out;
}
dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
__func__, break_reg[0], break_reg[1]);
if (break_state != 0) {
dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
break_reg[0] &= ~CH341_NBREAK_BITS;
break_reg[1] &= ~CH341_LCR_ENABLE_TX;
} else {
dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
break_reg[0] |= CH341_NBREAK_BITS;
break_reg[1] |= CH341_LCR_ENABLE_TX;
}
dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
__func__, break_reg[0], break_reg[1]);
reg_contents = get_unaligned_le16(break_reg);
r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
ch341_break_reg, reg_contents);
if (r < 0)
dev_err(&port->dev, "%s - USB control write error (%d)\n",
__func__, r);
out:
kfree(break_reg);
}
static int ch341_tiocmset(struct tty_struct *tty,
unsigned int set, unsigned int clear)
{
struct usb_serial_port *port = tty->driver_data;
struct ch341_private *priv = usb_get_serial_port_data(port);
unsigned long flags;
u8 control;
spin_lock_irqsave(&priv->lock, flags);
if (set & TIOCM_RTS)
priv->mcr |= CH341_BIT_RTS;
if (set & TIOCM_DTR)
priv->mcr |= CH341_BIT_DTR;
if (clear & TIOCM_RTS)
priv->mcr &= ~CH341_BIT_RTS;
if (clear & TIOCM_DTR)
priv->mcr &= ~CH341_BIT_DTR;
control = priv->mcr;
spin_unlock_irqrestore(&priv->lock, flags);
return ch341_set_handshake(port->serial->dev, control);
}
static void ch341_update_status(struct usb_serial_port *port,
unsigned char *data, size_t len)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
struct tty_struct *tty;
unsigned long flags;
u8 status;
u8 delta;
if (len < 4)
return;
status = ~data[2] & CH341_BITS_MODEM_STAT;
spin_lock_irqsave(&priv->lock, flags);
delta = status ^ priv->msr;
priv->msr = status;
spin_unlock_irqrestore(&priv->lock, flags);
if (data[1] & CH341_MULT_STAT)
dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
if (!delta)
return;
if (delta & CH341_BIT_CTS)
port->icount.cts++;
if (delta & CH341_BIT_DSR)
port->icount.dsr++;
if (delta & CH341_BIT_RI)
port->icount.rng++;
if (delta & CH341_BIT_DCD) {
port->icount.dcd++;
tty = tty_port_tty_get(&port->port);
if (tty) {
usb_serial_handle_dcd_change(port, tty,
status & CH341_BIT_DCD);
tty_kref_put(tty);
}
}
wake_up_interruptible(&port->port.delta_msr_wait);
}
static void ch341_read_int_callback(struct urb *urb)
{
struct usb_serial_port *port = urb->context;
unsigned char *data = urb->transfer_buffer;
unsigned int len = urb->actual_length;
int status;
switch (urb->status) {
case 0:
/* success */
break;
case -ECONNRESET:
case -ENOENT:
case -ESHUTDOWN:
/* this urb is terminated, clean up */
dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
__func__, urb->status);
return;
default:
dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
__func__, urb->status);
goto exit;
}
usb_serial_debug_data(&port->dev, __func__, len, data);
ch341_update_status(port, data, len);
exit:
status = usb_submit_urb(urb, GFP_ATOMIC);
if (status) {
dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
__func__, status);
}
}
static int ch341_tiocmget(struct tty_struct *tty)
{
struct usb_serial_port *port = tty->driver_data;
struct ch341_private *priv = usb_get_serial_port_data(port);
unsigned long flags;
u8 mcr;
u8 status;
unsigned int result;
spin_lock_irqsave(&priv->lock, flags);
mcr = priv->mcr;
status = priv->msr;
spin_unlock_irqrestore(&priv->lock, flags);
result = ((mcr & CH341_BIT_DTR) ? TIOCM_DTR : 0)
| ((mcr & CH341_BIT_RTS) ? TIOCM_RTS : 0)
| ((status & CH341_BIT_CTS) ? TIOCM_CTS : 0)
| ((status & CH341_BIT_DSR) ? TIOCM_DSR : 0)
| ((status & CH341_BIT_RI) ? TIOCM_RI : 0)
| ((status & CH341_BIT_DCD) ? TIOCM_CD : 0);
dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
return result;
}
static int ch341_reset_resume(struct usb_serial *serial)
{
struct usb_serial_port *port = serial->port[0];
struct ch341_private *priv;
int ret;
priv = usb_get_serial_port_data(port);
if (!priv)
return 0;
/* reconfigure ch341 serial port after bus-reset */
ch341_configure(serial->dev, priv);
if (tty_port_initialized(&port->port)) {
ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
if (ret) {
dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
ret);
return ret;
}
ret = ch341_get_status(port->serial->dev, priv);
if (ret < 0) {
dev_err(&port->dev, "failed to read modem status: %d\n",
ret);
}
}
return usb_serial_generic_resume(serial);
}
static struct usb_serial_driver ch341_device = {
.driver = {
.owner = THIS_MODULE,
.name = "ch341-uart",
},
.id_table = id_table,
.num_ports = 1,
.open = ch341_open,
.dtr_rts = ch341_dtr_rts,
.carrier_raised = ch341_carrier_raised,
.close = ch341_close,
.set_termios = ch341_set_termios,
.break_ctl = ch341_break_ctl,
.tiocmget = ch341_tiocmget,
.tiocmset = ch341_tiocmset,
.tiocmiwait = usb_serial_generic_tiocmiwait,
.read_int_callback = ch341_read_int_callback,
.port_probe = ch341_port_probe,
.port_remove = ch341_port_remove,
.reset_resume = ch341_reset_resume,
};
static struct usb_serial_driver * const serial_drivers[] = {
&ch341_device, NULL
};
module_usb_serial_driver(serial_drivers, id_table);
MODULE_LICENSE("GPL v2");
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