Commit 27aff0a5 authored by Marnix Rijnart's avatar Marnix Rijnart Committed by Greg Kroah-Hartman
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serial: 8250_pci: Fix broken RS485 for F81504/508/512 



Fintek F81504/508/512 can support both RTS_ON_SEND and RTS_AFTER_SEND,
but pci_fintek_rs485_supported only announces the former.

This makes it impossible to unset SER_RS485_RTS_ON_SEND from
userspace because of uart_sanitize_serial_rs485(). Some devices
with these chips need RTS low on TX, so they are effectively broken.

Fix this by announcing the support for SER_RS485_RTS_AFTER_SEND,
similar to commit 068d35a7 ("serial: sc16is7xx: announce support
for SER_RS485_RTS_ON_SEND").

Fixes: 4afeced5 ("serial: core: fix sanitizing check for RTS settings")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarMarnix Rijnart <marnix.rijnart@iwell.eu>
Link: https://patch.msgid.link/20260112000931.61703-1-marnix.rijnart@iwell.eu


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent fb47423d

drivers/tty/serial/8250/8250_pci.c

+1 −1
Original line number Diff line number Diff line
@@ -1658,7 +1658,7 @@ static int pci_fintek_rs485_config(struct uart_port *port, struct ktermios *term 
}



static const struct serial_rs485 pci_fintek_rs485_supported = {

	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND,

	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,

	/* F81504/508/512 does not support RTS delay before or after send */

};