From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794048538; b=TMy86rn87w62u91jPEg6pye+Is4997ybBtbscnBtQdjnmgceAoWi8y96oufTFH8a9CVb rPC0pLH3HDzrxzVxN8vvSI3MeZ9DbOnmqIEm8gszkv5rUjKyXbgW1zQxHFNV0/HoodPAB D1Cho1EXua/IlmUvqymC1A2ckwToUmOTm+mJ2l/ogDifQmvNmnqcuHZCXp9LvcVwE58aH eBqN7Mjxq5Cua8/IG8wUTQVqlkqJ47WdRZbj9JxQCrd1GBt6KvMDMPq7lYDAR+qbJ21dT hp1t0zh/7OTVKRdmeBkSxrZK0/9/pPUW0zuX3hcoKmh46q3sbPwWbk84apJHCXBa50A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794048538; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=Y+oxi70bZXREqHxpbeOsgkcuRylzPejVafSod6wIXkQ=; b=s3NfFEFwAyNRiMaFcZaJA/FHh4s7Hjxn58+lQNpqmYNQMNw7j58tHN2q+UDaTbkwW9WB 7wLb4z1o4aj1Z6DTBqawEYlLwv54EpC3tE4Yf16tKnMNMaDipLK+e5nq/EtkQKuRozihQ p43YygeTHNNMowujaCn3g/Oceu8Gy3J1tVhmcVM9H50pF8TesILYeyltcploLiq3YqoLN HyBfTNM61h3600zM83aPqgfDk/Ctw379cTlwHCggNX2g6/OT8DpjkNrZ58R7oL6CCMrqT jtng40qJtoC23cBVHlOWW4leR1ai905u52EnqHeDku3pCnNFucEIYyOcIWTQVl1XQ9w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VIAkx6fa; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E6C7606A326 for ; Sat, 7 Nov 2026 10:48:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VIAkx6fa Received: by smtp.kernel.org (Postfix) with ESMTPSA id 809F91F0089F; Sat, 7 Nov 2026 10:48:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794048537; bh=Y+oxi70bZXREqHxpbeOsgkcuRylzPejVafSod6wIXkQ=; h=From:To:Cc:Subject:Date; b=VIAkx6fa2o6fbXWnMLt4myraLdjNzmwUYuAtT+ePTj9yyxR/RergvEyqAoJg2X+C4 Yof7mqAudIpFi/hEeifHjvo+2TP/EpBahbQp/vDUiaNujjNYkXQBwNUcUwTjpIWooo RWz5kYtZ7HxD/NVkzvyXyB71jH0Zp2uzzejQZasQ0BIz/ppRhvfliQQEUTNuXuacB5 l5Hxze40UwFvXt3DYA81gntzF++PU1YLdwY1LMUiiVcZW59HJY+Ge3JM4CbM45QxS0 osZMUviUQvCPb0zegUQ0dJrW88hx2xQtuHWkj8KfZfFNHh7xwBaqveIW91IKqQ6WEO OPlOYLdVQ671Q== From: Sasha Levin To: nb@tipi-net.de, gregkh@linuxfoundation.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] serial: amba-pl011: keep transmitter enabled when disabling RS485" failed to apply to 6.1-stable tree Date: Sat, 7 Nov 2026 05:48:56 -0500 Message-ID: <20261107054856-failed-6.1-97f85204275a@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 97f85204275ae4d7fb530e451f3acc65c1ec1155 # git commit -s git send-email --to '' --in-reply-to '20261107054856-failed-6.1-97f85204275a@kernel.org' --subject-prefix 'PATCH 6.1.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 97f85204275ae4d7fb530e451f3acc65c1ec1155 Mon Sep 17 00:00:00 2001 From: Nicolai Buchwitz Date: Mon, 12 Oct 2026 16:23:50 +0200 Subject: [PATCH] serial: amba-pl011: keep transmitter enabled when disabling RS485 Disabling RS485 on an open port calls pl011_rs485_tx_stop(), which turns off the transmitter. Only the RS485 TX path turns it back on, so any later output stays queued and tcdrain() hangs until the port is closed. pl011_rs485_tx_stop() also checks only the hardware FIFO. If a DMA transfer has started but has not filled the FIFO yet, the transmitter is turned off under the transfer and the DMA channel never recovers. When leaving RS485 mode, cancel pending deferred starts and stops, leave the transmitter enabled and start any TX that was still waiting for delay_rts_before_send. Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support") Cc: stable@kernel.org Signed-off-by: Nicolai Buchwitz Link: https://patch.msgid.link/20261012-fix-pl011-rs485-txe-v2-1-e9bf7d218389@tipi-net.de Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/amba-pl011.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index cd8cbc9672815..3edd83ec73de1 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -2398,8 +2398,31 @@ static int pl011_rs485_config(struct uart_port *port, struct ktermios *termios, struct uart_amba_port *uap = container_of(port, struct uart_amba_port, port); - if (port->rs485.flags & SER_RS485_ENABLED) + if ((port->rs485.flags & SER_RS485_ENABLED) && + !(rs485->flags & SER_RS485_ENABLED)) { + bool tx_pending = uap->rs485_tx_state == WAIT_AFTER_RTS; + u32 cr = pl011_read(uap, REG_CR); + + /* + * Leaving RS485 mode, which only enables the transmitter while + * sending. Don't stop it, as that stalls a DMA transfer still + * in flight. Drop pending deferred starts and stops and keep + * it enabled. + */ + hrtimer_try_to_cancel(&uap->trigger_start_tx); + hrtimer_try_to_cancel(&uap->trigger_stop_tx); + uap->rs485_tx_state = OFF; + + cr |= UART011_CR_TXE | UART011_CR_RXE; + pl011_write(cr, uap, REG_CR); + + /* Start TX that was still waiting for delay_rts_before_send */ + if (tx_pending && !uart_tx_stopped(port) && + !pl011_dma_tx_start(uap)) + pl011_start_tx_pio(uap); + } else if (port->rs485.flags & SER_RS485_ENABLED) { pl011_rs485_tx_stop(uap); + } /* Make sure auto RTS is disabled */ if (rs485->flags & SER_RS485_ENABLED) { -- 2.53.0