Date: Wed, 04 Mar 2015 12:47:44 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 155752] [uart] tcdrain(3) does not work with uart(4) driver Message-ID: <bug-155752-8-77TeAglku2@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-155752-8@https.bugs.freebsd.org/bugzilla/> References: <bug-155752-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=155752 nkoch@demig.de changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |nkoch@demig.de --- Comment #1 from nkoch@demig.de --- I came across the same problem: I need to switch the transmitter of an external RS232/RS485 converter on before satarting transmittision and off afterwards using RTS. My quick driver hack is to always call the chip-specific drain function whenever there is a request to turn off RTS. This is my patch to the 16550 code: --- uart_dev_ns8250.c.orig 2015-03-04 13:37:04.000000000 +0100 +++ uart_dev_ns8250.c 2015-03-04 13:40:05.000000000 +0100 @@ -886,6 +886,10 @@ } } while (!atomic_cmpset_32(&sc->sc_hwsig, old, new)); uart_lock(sc->sc_hwmtx); +#ifdef UART_HACK_DRAIN_RTSOFF + if ((sig & SER_DRTS) && !(sig & SER_RTS)) + ns8250_drain(bas, UART_DRAIN_TRANSMITTER); +#endif ns8250->mcr &= ~(MCR_DTR|MCR_RTS); if (new & SER_DTR) ns8250->mcr |= MCR_DTR; The patch is against head but has been tested with 9.1 using a scope with protocol analyzer function. I did not look into the other chips' code so may it will not universally work. -- You are receiving this mail because: You are the assignee for the bug.
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