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Tue, 23 Sep 2025 15:19:49 -0700 (PDT) From: Marnix Rijnart To: Greg Kroah-Hartman , Jiri Slaby Cc: Marnix Rijnart , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, regressions@lists.linux.dev Subject: [REGRESSION][PATCH] serial: 8250_pci: Fix broken RS485 for F81504/508/512 Date: Wed, 24 Sep 2025 00:17:33 +0200 Message-ID: <20250923221756.26770-1-marnix.rijnart@iwell.eu> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Commit 4afeced ("serial: core: fix sanitizing check for RTS settings") introduced a regression making it impossible to unset SER_RS485_RTS_ON_SEND from userspace if SER_RS485_RTS_AFTER_SEND is unsupported. Because these devices need RTS to be low on TX (fecf27a) they are effectively broken. The hardware supports both RTS_ON_SEND and RTS_AFTER_SEND, so fix this by announcing support for SER_RS485_RTS_AFTER_SEND, similar to commit 068d35a. Signed-off-by: Marnix Rijnart --- drivers/tty/serial/8250/8250_pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8= 250_pci.c index 152f914c599d..a9da222bd174 100644 --- a/drivers/tty/serial/8250/8250_pci.c +++ b/drivers/tty/serial/8250/8250_pci.c @@ -1645,7 +1645,7 @@ static int pci_fintek_rs485_config(struct uart_port *= port, struct ktermios *term } =20 static const struct serial_rs485 pci_fintek_rs485_supported =3D { - .flags =3D SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND, + .flags =3D SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTE= R_SEND, /* F81504/508/512 does not support RTS delay before or after send */ }; =20 --=20 2.51.0