From 9ad221a558f813645e352036ee2445903d9a9b6f Mon Sep 17 00:00:00 2001 From: Ian Lepore Date: Sun, 5 Feb 2017 15:45:31 +0000 Subject: Add tsw_busy support to usb_serial (ucom). 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 --- sys/dev/usb/serial/usb_serial.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'sys/dev/usb/serial/usb_serial.c') diff --git a/sys/dev/usb/serial/usb_serial.c b/sys/dev/usb/serial/usb_serial.c index 23ee3305a181..c5fc14b41b4d 100644 --- a/sys/dev/usb/serial/usb_serial.c +++ b/sys/dev/usb/serial/usb_serial.c @@ -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 * -- cgit v1.2.3