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=1794049572; b=Nrv6DCX5eCiEAJz1G7/p0ufNV0X5GwdnpTMfvrVqZE66eYcwSnNLK5c84WugSXqX4mHE k6XLWrdq0ec5uUCAbDWUk5Ke1GfCQzqovrv1R1K0SHoGarI7HPDaUapHoStPVAs+4A4XH pm4oAxIKcJ4cN1avekzobUxiuBeM29YzGZccY8GKrgWjVbX25vtfW4tdRXzBQ/1hW1w0l 17S7tLLQ3YHXG9FEro8FErwNuTqFobnLttRWQ2CZP4yptRy9JRHBkhZFSq6ZBrTBKdWEq eoqA+lPaf6ryXTA//Js4fUoByA2tPXFIu+oD9AIs9X1qEIPfu3ObLroXAXsvz+oi9bA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049572; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=x3lvonrf6Nmd3uyGTgiPnTXFG6zYH7LMOWYZyfkTbgg=; b=bT6TYfssQK0o8ilCJXVNtnvNsHe9BMrvDeylzLb6CCB4Y27p595FUpBCEQ0ZWeMnqlkj kvXqxFJLMWojdbbPfisrGGk1oVjKjQ2FkSG5Eo4W3t9RiJIS58ejibmOyRoMbKZhneAF5 ARpaZ4WTMAovjIC+IPNtoflACFQqmcFNv0VXN/K4+/YnGZF5np4efKg3pySfa3jeZ/wcv fS444Q1RUBfBrVKiUzQg1ke/tVnAELNDjnVfBo3SLnx5Suipr5VMBotO7oAGyxTuJ8pMZ P2MWqIrbPNo0fcExh6ttwK4LLAPnV3G8EPdliKYYN6cXcD8VWZnQSIqqeYEOypG9QZg== 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=dntUohyT; 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 3584B606A336 for ; Sat, 7 Nov 2026 11:06:12 +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=dntUohyT Received: by smtp.kernel.org (Postfix) with ESMTPSA id A89F51F008A2; Sat, 7 Nov 2026 11:06:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049572; bh=x3lvonrf6Nmd3uyGTgiPnTXFG6zYH7LMOWYZyfkTbgg=; h=From:To:Cc:Subject:Date; b=dntUohyTgFS4alpgtLxTuL+6H+DdSI/gMVorXr/yJsD9yxj0mp+CbjConklo67z1B ROQ2YBGaieyW6WZLyg2ZaOu5bna47EPFVffwgVJtPMo+g6ex8dFy3pc7NHYPAHT+c0 hEGrtzmmX3Z9HxHMnRQlNMQ4VquKB4mxn9Sjru1IPyiJYE0qitivSRMiI3SXS5M2nZ 0MPj7/ub59KGh/Tg/3guH2qdM0vfhwFDEbYC4BfYuFJ7ovMStOTYMFw0WkPaA9Yjh6 qb/dwmCpSCbh0Xp0qd9wcyiQFiOOjoZu+2kCWMJXvIxxzpIXPUbdGbTll0OmeHzX6s sUeNLAQ5SHHpQ== 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 5.15-stable tree Date: Sat, 7 Nov 2026 06:06:10 -0500 Message-ID: <20261107060610-failed-5.15-97f85204275a@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x 97f85204275ae4d7fb530e451f3acc65c1ec1155 # git commit -s git send-email --to '' --in-reply-to '20261107060610-failed-5.15-97f85204275a@kernel.org' --subject-prefix 'PATCH 5.15.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