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Add tsw_busy support to usb_serial (ucom).

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The tty layer uses tsw_busy to poll for busy/idle status of the transmitter
hardware during close() and tcdrain(). The ucom layer defines ULSR_TXRDY and
ULSR_TSRE bits for the line status register; when both are set, the
transmitter is idle. Not all chip drivers maintain those bits in the sc_lsr
field, and if the bits never get set the transmitter will always appear
busy, causing hangs in tcdrain().

These changes add a new sc_flag bit, UCOM_FLAG_LSRTXIDLE. When this flag is
set, ucom_busy() uses the lsr bits to return busy vs. idle state, otherwise
it always returns idle (which is effectively what happened before this
change because tsw_busy wasn't implemented).

For the uftdi chip driver, these changes stop masking out the tx idle bits
when processing the status register (because now they're useful), and it
calls ucom_use_lsr_txbits() to indicate the bits are maintained by the
driver and can be used by ucom_busy().

Differential Revision:	https://reviews.freebsd.org/D9183
This commit is contained in:
Ian Lepore 2017-02-05 15:45:31 +00:00
parent 12bc0fb56f
commit 9ad221a558
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=313287
3 changed files with 44 additions and 6 deletions
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18
sys/dev/usb/serial/uftdi.c
View file

@ -1123,6 +1123,9 @@ uftdi_attach(device_t dev)
FTDI_SIO_SET_DATA_PARITY_NONE |
FTDI_SIO_SET_DATA_BITS(8));
/* Indicate tx bits in sc_lsr can be used to determine busy vs idle. */
ucom_use_lsr_txbits(&sc->sc_ucom);
error = ucom_attach(&sc->sc_super_ucom, &sc->sc_ucom, 1, sc,
&uftdi_callback, &sc->sc_mtx);
if (error) {
@ -1279,16 +1282,20 @@ uftdi_read_callback(struct usb_xfer *xfer, usb_error_t error)
offset = 0;
/*
* Extract packet headers and payload bytes from the buffer.
* Feed payload bytes to ucom/tty layer; OR-accumulate header
* status bits which are transient and could toggle with each
* packet. After processing all packets in the buffer, process
* the accumulated transient MSR and LSR values along with the
* Feed payload bytes to ucom/tty layer; OR-accumulate the
* receiver-related header status bits which are transient and
* could toggle with each packet, but for transmitter-related
* bits keep only the ones from the last packet.
*
* After processing all packets in the buffer, process the
* accumulated transient MSR and LSR values along with the
* non-transient bits from the last packet header.
*/
while (buflen >= UFTDI_IHDRSIZE) {
usbd_copy_out(pc, offset, buf, UFTDI_IHDRSIZE);
offset += UFTDI_IHDRSIZE;
buflen -= UFTDI_IHDRSIZE;
lsr &= ~(ULSR_TXRDY | ULSR_TSRE);
lsr |= FTDI_GET_LSR(buf);
if (FTDI_GET_MSR(buf) & FTDI_SIO_RI_MASK)
msr |= SER_RI;
@ -1311,8 +1318,7 @@ uftdi_read_callback(struct usb_xfer *xfer, usb_error_t error)
if (ftdi_msr & FTDI_SIO_RLSD_MASK)
msr |= SER_DCD;
if ((sc->sc_msr != msr) ||
((sc->sc_lsr & FTDI_LSR_MASK) != (lsr & FTDI_LSR_MASK))) {
if (sc->sc_msr != msr || sc->sc_lsr != lsr) {
DPRINTF("status change msr=0x%02x (0x%02x) "
"lsr=0x%02x (0x%02x)\n", msr, sc->sc_msr,
lsr, sc->sc_lsr);

23
sys/dev/usb/serial/usb_serial.c
View file

@ -161,6 +161,7 @@ static tsw_param_t ucom_param;
static tsw_outwakeup_t ucom_outwakeup;
static tsw_inwakeup_t ucom_inwakeup;
static tsw_free_t ucom_free;
static tsw_busy_t ucom_busy;
static struct ttydevsw ucom_class = {
.tsw_flags = TF_INITLOCK | TF_CALLOUT,
@ -172,6 +173,7 @@ static struct ttydevsw ucom_class = {
.tsw_param = ucom_param,
.tsw_modem = ucom_modem,
.tsw_free = ucom_free,
.tsw_busy = ucom_busy,
};
MODULE_DEPEND(ucom, usb, 1, 1, 1);
@ -1294,6 +1296,27 @@ ucom_outwakeup(struct tty *tp)
ucom_start_transfers(sc);
}
static bool
ucom_busy(struct tty *tp)
{
struct ucom_softc *sc = tty_softc(tp);
const uint8_t txidle = ULSR_TXRDY | ULSR_TSRE;
UCOM_MTX_ASSERT(sc, MA_OWNED);
DPRINTFN(3, "sc = %p lsr 0x%02x\n", sc, sc->sc_lsr);
/*
* If the driver maintains the txidle bits in LSR, we can use them to
* determine whether the transmitter is busy or idle. Otherwise we have
* to assume it is idle to avoid hanging forever on tcdrain(3).
*/
if (sc->sc_flag & UCOM_FLAG_LSRTXIDLE)
return ((sc->sc_lsr & txidle) != txidle);
else
return (false);
}
/*------------------------------------------------------------------------*
* ucom_get_data
*

9
sys/dev/usb/serial/usb_serial.h
View file

@ -180,6 +180,7 @@ struct ucom_softc {
#define UCOM_FLAG_WAIT_REFS 0x0100 /* set if we must wait for refs */
#define UCOM_FLAG_FREE_UNIT 0x0200 /* set if we must free the unit */
#define UCOM_FLAG_INWAKEUP 0x0400 /* set if we are in the tsw_inwakeup callback */
#define UCOM_FLAG_LSRTXIDLE 0x0800 /* set if sc_lsr bits ULSR_TSRE+TXRDY work */
uint8_t sc_lsr;
uint8_t sc_msr;
uint8_t sc_mcr;
@ -218,4 +219,12 @@ void ucom_drain(struct ucom_super_softc *);
void ucom_drain_all(void *);
void ucom_ref(struct ucom_super_softc *);
int ucom_unref(struct ucom_super_softc *);
static inline void
ucom_use_lsr_txbits(struct ucom_softc *sc)
{
sc->sc_flag |= UCOM_FLAG_LSRTXIDLE;
}
#endif /* _USB_SERIAL_H_ */