From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2466114A4C7; Wed, 7 May 2025 18:43:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746643416; cv=none; b=jwPqkoGRU8kdUwt8xMhBVYA1kiNDL4eUKUP9mvJe3/ZtIOil5SOZiwjvuIeXwzgoBAOB0q4Za/FnU7mzbe6KxSsp6CbZhGlUlQvfOnmDyAK489PEZO4/oBIs4WdZMWgSvQRVWVdcQAYnDvLOC7goYzYK2Wn48586HkhNhRcg6/4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746643416; c=relaxed/simple; bh=dh+HlsJwDhAxXvnJ0ejUwtoDaz53WdvMlPvJ2VJtkxk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fsqVWV7OJhmtTY2DwZmrpPpXvFKBhKcij0yNrMYUQgrvAZBGtVTAYEiDGGUDkAqY+Yvtg5k5LpMgEfZ+/TRNXa4wlsf8K8s8ZPU2qy7Ff24v/EdiL45FU6AMlgg2Ndhm6TjvTEcvwSU8dz9wfFxI3J2XYuKjA58W75yxVXsjPQA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=he1tcrBh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="he1tcrBh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1066C4CEE2; Wed, 7 May 2025 18:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1746643416; bh=dh+HlsJwDhAxXvnJ0ejUwtoDaz53WdvMlPvJ2VJtkxk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=he1tcrBhz/DbMUEbOkQmuX6V1gIuAcb4/M2hR8oPhGS5dsK9A3Sr8eKMRjUuxFLoT xg1vT/R51fyNf23FPQyPd57X0zp2CvrawDlW5wNskr0C3u+rKlhQpe4W4BETT2gYb1 RSYZ/uoANlrTfwqf4H6KA5fEnG1DceQ6kgqADUYo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Stephan Gerhold , Neil Armstrong , Sasha Levin Subject: [PATCH 5.15 52/55] serial: msm: Configure correct working mode before starting earlycon Date: Wed, 7 May 2025 20:39:53 +0200 Message-ID: <20250507183801.137268867@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250507183759.048732653@linuxfoundation.org> References: <20250507183759.048732653@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stephan Gerhold [ Upstream commit 7094832b5ac861b0bd7ed8866c93cb15ef619996 ] The MSM UART DM controller supports different working modes, e.g. DMA or the "single-character mode", where all reads/writes operate on a single character rather than 4 chars (32-bit) at once. When using earlycon, __msm_console_write() always writes 4 characters at a time, but we don't know which mode the bootloader was using and we don't set the mode either. This causes garbled output if the bootloader was using the single-character mode, because only every 4th character appears in the serial console, e.g. "[ 00oni pi 000xf0[ 00i s 5rm9(l)l s 1 1 SPMTA 7:C 5[ 00A ade k d[ 00ano:ameoi .Q1B[ 00ac _idaM00080oo'" If the bootloader was using the DMA ("DM") mode, output would likely fail entirely. Later, when the full serial driver probes, the port is re-initialized and output works as expected. Fix this also for earlycon by clearing the DMEN register and reset+re-enable the transmitter to apply the change. This ensures the transmitter is in the expected state before writing any output. Cc: stable Fixes: 0efe72963409 ("tty: serial: msm: Add earlycon support") Signed-off-by: Stephan Gerhold Reviewed-by: Neil Armstrong Link: https://lore.kernel.org/r/20250408-msm-serial-earlycon-v1-1-429080127530@linaro.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/msm_serial.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c index 03ff63438e772..9740bc301cc27 100644 --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -1732,6 +1732,12 @@ msm_serial_early_console_setup_dm(struct earlycon_device *device, if (!device->port.membase) return -ENODEV; + /* Disable DM / single-character modes */ + msm_write(&device->port, 0, UARTDM_DMEN); + msm_write(&device->port, MSM_UART_CR_CMD_RESET_RX, MSM_UART_CR); + msm_write(&device->port, MSM_UART_CR_CMD_RESET_TX, MSM_UART_CR); + msm_write(&device->port, MSM_UART_CR_TX_ENABLE, MSM_UART_CR); + device->con->write = msm_serial_early_write_dm; return 0; } -- 2.39.5