On Thu, Oct 27, 2022 at 09:19:43AM +0900, Dominique Martinet wrote: > From: Lukas Wunner <lukas@xxxxxxxxx> > > When a UART port is newly registered, uart_configure_port() seeks to > deassert RS485 Transmit Enable by setting the RTS bit in port->mctrl. > However a number of UART drivers interpret a set RTS bit as *assertion* > instead of deassertion: Affected drivers include those using > serial8250_em485_config() (except 8250_bcm2835aux.c) and some using > mctrl_gpio (e.g. imx.c). > > Since the interpretation of the RTS bit is driver-specific, it is not > suitable as a means to centrally deassert Transmit Enable in the serial > core. Instead, the serial core must call on drivers to deassert it in > their driver-specific way. One way to achieve that is to call > ->rs485_config(). It implicitly deasserts Transmit Enable. > > So amend uart_configure_port() and uart_resume_port() to invoke > uart_rs485_config(). That allows removing calls to uart_rs485_config() > from drivers' ->probe() hooks and declaring the function static. > > Skip any invocation of ->set_mctrl() if RS485 is enabled. RS485 has no > hardware flow control, so the modem control lines are irrelevant and > need not be touched. When leaving RS485 mode, reset the modem control > lines to the state stored in port->mctrl. That way, UARTs which are > muxed between RS485 and RS232 transceivers drive the lines correctly > when switched to RS232. (serial8250_do_startup() historically raises > the OUT1 modem signal because otherwise interrupts are not signaled on > ancient PC UARTs, but I believe that no longer applies to modern, > RS485-capable UARTs and is thus safe to be skipped.) > > imx.c modifies port->mctrl whenever Transmit Enable is asserted and > deasserted. Stop it from doing that so port->mctrl reflects the RS232 > line state. > > 8250_omap.c deasserts Transmit Enable on ->runtime_resume() by calling > ->set_mctrl(). Because that is now a no-op in RS485 mode, amend the > function to call serial8250_em485_stop_tx(). > > fsl_lpuart.c retrieves and applies the RS485 device tree properties > after registering the UART port. Because applying now happens on > registration in uart_configure_port(), move retrieval of the properties > ahead of uart_add_one_port(). > > [ Upstream commit 7c7f9bc986e698873b489c371a08f206979d06b7 ] > Link: https://lkml.kernel.org/r/20221017051737.51727-2-dominique.martinet@xxxxxxxxxxxxxxxxx > Link: https://lore.kernel.org/all/20220329085050.311408-1-matthias.schiffer@xxxxxxxxxxxxxxx/ > Link: https://lore.kernel.org/all/8f538a8903795f22f9acc94a9a31b03c9c4ccacb.camel@xxxxxxxxxxxxx/ > Fixes: d3b3404df318 ("serial: Fix incorrect rs485 polarity on uart open") > Cc: stable@xxxxxxxxxxxxxxx # v4.14+ > Reported-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> > Reported-by: Roosen Henri <Henri.Roosen@xxxxxxxxxxxxx> > Tested-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > Link: https://lore.kernel.org/r/2de36eba3fbe11278d5002e4e501afe0ceaca039.1663863805.git.lukas@xxxxxxxxx > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Daisuke Mizobuchi <mizo@xxxxxxxxxxxxxxxxx> > Signed-off-by: Dominique Martinet <dominique.martinet@xxxxxxxxxxxxxxxxx> > --- > > 5.15 version of the 5.10 patch: > https://lkml.kernel.org/r/20221017051737.51727-2-dominique.martinet@xxxxxxxxxxxxxxxxx > (only build tested) Both now queued up, thanks. greg k-h
