From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout01.posteo.de (mout01.posteo.de [185.67.36.65]) (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 331115111A7 for ; Wed, 30 Sep 2026 15:33:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.67.36.65 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790782429; cv=none; b=FiA9pg1zB4d35I562ny/xTbE6pynEwWVJlsbkhHnJEd60P6vyyoejOXMm2ynXDTGS7dK7VC2nNofGgwQ7fOzkSq1lkmOYuk5PEWPLN/Q3pPxkUaUxZqmcmPN5BzFEM/DlPnKZIUYF+rtSrd+PQk/CrffY04JxrpmvCBuZUlRHbE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790782429; c=relaxed/simple; bh=GF3qJ28po4tzQKhOOmc1ZjYhXtmA/fVN39S6nEBHPRI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=P9hbHV4cH99z2yX3Emy95Y2tMiFVIbevJ2PhYpXkl5v7VAAjn4hgjjkKr2pwPU8/FFB6L5FTkWbGQMiQUT3sUtZtrLLvUPmT6OAsRof2zExzqybmt3otPZ0toWllJ9J/t+A09lwj6zx4Z/dKewQjns3Zkn5qqpb707oPUBlOURc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de; spf=pass smtp.mailfrom=posteo.de; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b=YlSUyJKY; arc=none smtp.client-ip=185.67.36.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=posteo.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b="YlSUyJKY" Received: from submission (posteo.de [185.67.36.169]) by mout01.posteo.de (Postfix) with ESMTPS id 43045240027 for ; Wed, 30 Sep 2026 17:33:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=1984.8680eb; t=1790782411; bh=4KZfnZZWUgpacNaNvWb37H6nYeezWlIgqRQQEVtr3Zc=; h=From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:To:Cc:Autocrypt:OpenPGP:From; b=YlSUyJKYIpbHJ50TtBkxm74jrB0lfD9DhChK3MGWXp1SPMU4zcFlG0/yaDvGd1dnM fcF8GibA2Zgv+9BC53yUY0ffAqA0YR4k2bJ1ofw7HCid9SNrbvGMMQmXHDv16Gcs7D 6lIC9UTxpKX5052h3F4TL/fRwYgKGlVCzFD7N8RuhnCtVOd7nKJjcbOqX5b/a706Gh g007QfKoypluU01hgC3mptJS1dOZHLdE64EnunDGG333Ci0UomkuHimXvtIvfWzCvb mIY9amZa8FpJAEyAGcXaoD02lFax9SsEF60f3d5h9kSsIOHxANE6VMmtwUveL2hQy+ D1jQ7N/7f3OPA== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4hvzbG3q93z6tyf; Wed, 30 Sep 2026 17:33:30 +0200 (CEST) From: Markus Probst Date: Wed, 30 Sep 2026 15:33:31 +0000 Subject: [PATCH RESEND v4] ACPI: SPCR: Support UART clock frequency field Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260930-acpi_spcr-v4-1-ab649aa1f09c@posteo.de> To: Greg Kroah-Hartman , Jiri Slaby , "Rafael J. Wysocki" , Len Brown Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-acpi@vger.kernel.org, Markus Probst X-Developer-Signature: v=1; a=openpgp-sha256; l=6200; i=markus.probst@posteo.de; h=from:subject:message-id; bh=GF3qJ28po4tzQKhOOmc1ZjYhXtmA/fVN39S6nEBHPRI=; b=owEBiQJ2/ZANAwAIATR2H/jnrUPSAcsmYgBqvSvKFi07fAaGbO91OnxOyzL/xJ1SWeUKGIYOK RxkAon479aJAk8EAAEIADkWIQSCdBjE9KxY53IwxHM0dh/4561D0gUCar0ryhsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMiwyLDIACgkQNHYf+OetQ9KZhg//YZVNysLcXV/5KG8JMHy8OdJaNhz5FIm 03Xmvro/oqzi71pxT/K0zCi/Wk5DVlvzKj0dtV/jUtQpG7UPRUUJmESSbh0hHCsOvpJnLJ+hwac 0oQMFcCTo8Mgnx8ckiqJyf5DTGL/22d7CWBo7MsvyivhmZf/51E/DFQMC1OgdpFP3ZB/AJRl2oN jUo9/OOFnr7d9IURst8yu6Lr2XdJsbeu/+RDxXHolY28tMz4816n8N7YrFgK9mooMbIjs1J0/DZ LXeil9JEpu/rfNq65A2CSXrGPhmunQjZ2DhT4c15pSoj8H/IrNkt8ZxMPP7Mn4ix+CW1Tkuppul sBDTr1ag6x3gLkCzt+7Inutp1ooBQeEQppj+AYkGHAgQ+jmT7Bbe1lSxiqbn/jflS/YvPPIFYtE ddIMmmZF2UBHlZ1lNBkIG7ul77AEvkeLYXxuNzYZWf5xZnpTx51qsykJN3MZKcKKUc/Rj+Bq9UP y8pVncgMeakEvi4xrn6H3SEtjFWGenoa8/YdRY3iG72mXuyZgDApTv8MhNL5FNSGnH75Go7Jiqy 96n9iBYBMa7s91QPnYHq2ZMFnPAIjLtkQ781kNAMwO9S+wDjrjrSLRI6bq2gtvH5r2fKRVWcLE/ zAandPdwCWRKbQY4j3XtC+4F2HnOXGBiRFAqIjTPRBda0PT9LVcQ= X-Developer-Key: i=markus.probst@posteo.de; a=openpgp; fpr=827418C4F4AC58E77230C47334761FF8E7AD43D2 Autocrypt: addr=markus.probst@posteo.de; prefer-encrypt=mutual; keydata=xsFNBGiDvXgBEADAXUceKafpl46S35UmDh2wRvvx+UfZbcTjeQOlSwKP7YVJ4JOZrVs93qReNLkO WguIqPBxR9blQ4nyYrqSCV+MMw/3ifyXIm6Pw2YRUDg+WTEOjTixRCoWDgUj1nOsvJ9tVAm76Ww+ /pAnepVRafMID0rqEfD9oGv1YrfpeFJhyE2zUw3SyyNLIKWD6QeLRhKQRbSnsXhGLFBXCqt9k5JA RhgQof9zvztcCVlT5KVvuyfC4H+HzeGmu9201BVyihJwKdcKPq+n/aY5FUVxNTgtI9f8wIbmfAja oT1pjXSp+dszakA98fhONM98pOq723o/1ZGMZukyXFfsDGtA3BB79HoopHKujLGWAGskzClwTjRQ xBqxh/U/lL1pc+0xPWikTNCmtziCOvv0KA0arDOMQlyFvImzX6oGVgE4ksKQYbMZ3Ikw6L1Rv1J+ FvN0aNwOKgL2ztBRYscUGcQvA0Zo1fGCAn/BLEJvQYShWKeKqjyncVGoXFsz2AcuFKe1pwETSsN6 OZncjy32e4ktgs07cWBfx0v62b8md36jau+B6RVnnodaA8++oXl3FRwiEW8XfXWIjy4umIv93tb8 8ekYsfOfWkTSewZYXGoqe4RtK80ulMHb/dh2FZQIFyRdN4HOmB4FYO5sEYFr9YjHLmDkrUgNodJC XCeMe4BO4iaxUQARAQABzRdtYXJrdXMucHJvYnN0QHBvc3Rlby5kZcLBkQQTAQgAOxYhBIJ0GMT0 rFjncjDEczR2H/jnrUPSBQJog714AhsDBQsJCAcCAiICBhUKCQgLAgQWAgMBAh4HAheAAAoJEDR2 H/jnrUPSgdkQAISaTk2D345ehXEkn5z2yUEjaVjHIE7ziqRaOgn/QanCgeTUinIv6L6QXUFvvIfH 1OLPwQ1hfvEg9NnNLyFezWSy6jvoVBTIPqicD/r3FkithnQ1IDkdSjrarPMxJkvuh3l7XZHo49GV HQ8i5zh5w4YISrcEtE99lJisvni2Jqx7we5tey9voQFDyM8jxlSWv3pmoUTCtBkX/eKHJXosgsuS B4TGDCVPOjla/emI5c9MhMG7O4WEEmoSdPbmraPw66YZD6uLyhV4DPHbiDWRzXWnClHSyjB9rky9 lausFxogvu4l9H+KDsXIadNDWdLdu1/enS/wDd9zh5S78rY2jeXaG4mnf4seEKamZ7KQ6FIHrcyP ezdDzssPQcTQcGRMQzCn6wP3tlGk7rsfmyHMlFqdRoNNv+ZER/OkmZFPW655zRfbMi0vtrqK2Awm 9ggobb1oktfd9PPNXMUY+DNVlgR2G7jLnenSoQausLUm0pHoNE8TWFv851Y6SOYnvn488sP1Tki5 F3rKwclawQFHUXTCQw+QSh9ay8xgnNZfH+u9NY7w3gPoeKBOAFcBc2BtzcgekeWS8qgEmm2/oNFV G0ivPQbRx8FjRKbuF7g3YhgNZZ0ac8FneuUtJ2PkSIFTZhaAiC0utvxk0ndmWFiW4acEkMZGrLaM L2zWNjrqwsD2zsFNBGiDvXgBEADCXQy1n7wjRxG12DOVADawjghKcG+5LtEf31WftHKLFbp/HArj BhkT6mj+CCI1ClqY+FYU5CK/s0ScMfLxRGLZ0Ktzawb78vOgBVFT3yB1yWBTewsAXdqNqRooaUNo 8cG/NNJLjhccH/7PO/FWX5qftOVUJ/AIsAhKQJ18Tc8Ik73v427EDxuKb9mTAnYQFA3Ev3hAiVbO 6Rv39amVOfJ8sqwiSUGidj2Fctg2aB5JbeMln0KCUbTD1LhEFepeKypfofAXQbGwaCjAhmkWy/q3 IT1mUrPxOngbxdRoOx1tGUC0HCMUW1sFaJgQPMmDcR0JGPOpgsKnitsSnN7ShcCr1buel7vLnUMD +TAZ5opdoF6HjAvAnBQaijtK6minkrM0seNXnCg0KkV8xhMNa6zCs1rq4GgjNLJue2EmuyHooHA4 7JMoLVHcxVeuNTp6K2+XRx0Pk4e2Lj8IVy9yEYyrywEOC5XRW37KJjsiOAsumi1rkvM7QREWgUDe Xs0+RpxI3QrrANh71fLMRo7LKRF3Gvw13NVCCC9ea20P4PwhgWKStkwO2NO+YJsAoS1QycMi/vKu 0EHhknYXamaSV50oZzHKmX56vEeJHTcngrM8R1SwJCYopCx9gkz90bTVYlitJa5hloWTYeMD7FNj Y6jfVSzgM/K4gMgUNDW/PPGeMwARAQABwsF2BBgBCAAgFiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IF AmiDvXgCGwwACgkQNHYf+OetQ9LHDBAAhk+ab8+WrbS/b1/gYW3q1KDiXU719nCtfkUVXKidW5Ec Idlr5HGt8ilLoxSWT2Zi368iHCXS0WenGgPwlv8ifvB7TOZiiTDZROZkXjEBmU4nYjJ7GymawpWv oQwjMsPuq6ysbzWtOZ7eILx7cI0FjQeJ/Q2baRJub0uAZNwBOxCkAS6lpk5Fntd2u8CWmDQo4SYp xeuQ+pwkp0yEP30RhN2BO2DXiBEGSZSYh+ioGbCHQPIV3iVj0h6lcCPOqopZqyeCfigeacBI0nvN jHWz/spzF3+4OS+3RJvoHtAQmProxyGib8iVsTxgZO3UUi4TSODeEt0i0kHSPY4sCciOyXfAyYoD DFqhRjOEwBBxhr+scU4C1T2AflozvDwq3VSONjrKJUkhd8+WsdXxMdPFgBQuiKKwUy11mz6KQfcR wmDehF3UaUoxa+YIhWPbKmycxuX/D8SvnqavzAeAL1OcRbEI/HsoroVlEFbBRNBZLJUlnTPs8ZcU 4+8rq5YX1GUrJL3jf6SAfSgO7UdkEET3PdcKFYtS+ruV1Cp5V0q4kCfI5jk25iiz8grM2wOzVSsc l1mEkhiEPH87HP0whhb544iioSnumd3HJKL7dzhRegsMizatupp8D65A2JziW0WKopa1iw9fti3A aBeNN4ijKZchBXHPgVx+YtWRHfcm4l8= OpenPGP: url=https://posteo.de/keys/markus.probst@posteo.de.asc; preference=encrypt Prior to this patch, we assume the uart clock frequency is 1843200 Hz in the early console. This behaviour results in garbage console output if the actual uart clock frequency differs. The UART Clock Frequency field was added in the Microsoft Serial Port Console Redirection (SPCR) specification revision 1.08. If present, use it to configure the serial port with the correct uart clock frequency. Fallback to old behaviour if missing. Add function `setup_earlycon_with_uartclk` to set uart clock frequency while still allowing to reuse the same console string with `add_preferred_console`. Link: https://learn.microsoft.com/en-us/windows-hardware/drivers/serports/serial-port-console-redirection-table Signed-off-by: Markus Probst --- Changes in v4: - merge patches together - rewrite commit message - Link to v3: https://patch.msgid.link/20260615-acpi_spcr-v3-0-9a59ebad74ea@posteo.de Changes in v3: - add separate function for earlycon with uartclk - Link to v2: https://patch.msgid.link/20260525-acpi_spcr-v2-0-c042089d73ca@posteo.de Changes in v2: - fix uart_clk_freq possibly being interpreted as parity/bits/flow - Link to v1: https://patch.msgid.link/20260505-acpi_spcr-v1-1-fd4bc6f4eb53@posteo.de --- drivers/acpi/spcr.c | 3 ++- drivers/tty/serial/earlycon.c | 17 ++++++++++++----- include/linux/serial_core.h | 11 +++++++++-- 3 files changed, 23 insertions(+), 8 deletions(-) diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c index 73cb933fdc89..c79c809f49d4 100644 --- a/drivers/acpi/spcr.c +++ b/drivers/acpi/spcr.c @@ -228,7 +228,8 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console) pr_info("console: %s\n", opts); if (enable_earlycon) - setup_earlycon(opts); + setup_earlycon_with_uartclk(opts, + table->header.revision >= 3 ? table->uart_clk_freq : 0); if (enable_console) err = add_preferred_console(uart, 0, opts + strlen(uart) + 1); diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c index ab9af37f6cda..5a20fe9e3fb6 100644 --- a/drivers/tty/serial/earlycon.c +++ b/drivers/tty/serial/earlycon.c @@ -135,11 +135,14 @@ static int __init parse_options(struct earlycon_device *device, char *options) return 0; } -static int __init register_earlycon(char *buf, const struct earlycon_id *match) +static int __init register_earlycon(char *buf, unsigned int uart_clk_freq, + const struct earlycon_id *match) { int err; struct uart_port *port = &early_console_dev.port; + port->uartclk = uart_clk_freq; + /* On parsing error, pass the options buf to the setup function */ if (buf && !parse_options(&early_console_dev, buf)) buf = NULL; @@ -163,8 +166,9 @@ static int __init register_earlycon(char *buf, const struct earlycon_id *match) } /** - * setup_earlycon - match and register earlycon console - * @buf: earlycon param string + * setup_earlycon_with_uartclk - match and register earlycon console + * @buf: earlycon param string + * @uart_clk_freq: uart clock frequency in Hz or 0 for BASE_BAUD*16 * * Registers the earlycon console matching the earlycon specified * in the param string @buf. Acceptable param strings are of the form @@ -177,10 +181,13 @@ static int __init register_earlycon(char *buf, const struct earlycon_id *match) * string in the 'options' parameter; all other forms set * the parameter to NULL. * + * If the uart clock frequency is specified in the 'options' parameter, + * the value of the param @uart_clk_freq will be ignored. + * * Returns 0 if an attempt to register the earlycon was made, * otherwise negative error code */ -int __init setup_earlycon(char *buf) +int __init setup_earlycon_with_uartclk(char *buf, unsigned int uart_clk_freq) { const struct earlycon_id *match; bool empty_compatible = true; @@ -209,7 +216,7 @@ int __init setup_earlycon(char *buf) } else buf = NULL; - return register_earlycon(buf, match); + return register_earlycon(buf, uart_clk_freq, match); } if (empty_compatible) { diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index bdc214386e4a..9b2bcd4295a9 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -1099,11 +1099,18 @@ int of_setup_earlycon(const struct earlycon_id *match, unsigned long node, #ifdef CONFIG_SERIAL_EARLYCON extern bool earlycon_acpi_spcr_enable __initdata; -int setup_earlycon(char *buf); +int setup_earlycon_with_uartclk(char *buf, unsigned int uart_clk_freq); #else static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED; -static inline int setup_earlycon(char *buf) { return 0; } +static inline int setup_earlycon_with_uartclk(char *buf, unsigned int uart_clk_freq) +{ + return 0; +} #endif +static inline int setup_earlycon(char *buf) +{ + return setup_earlycon_with_uartclk(buf, 0); +} /* Variant of uart_console_registered() when the console_list_lock is held. */ static inline bool uart_console_registered_locked(struct uart_port *port) --- base-commit: 237a1c39e8dfd3e1c6f1f023eea37a48ec04cc63 change-id: 20260430-acpi_spcr-61902fd923f2 -----BEGIN PGP SIGNATURE----- iQJPBAABCAA5FiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IFAmqOIQQbFIAAAAAABAAO bWFudTIsMi41KzEuMTIsMiwyAAoJEDR2H/jnrUPSt08QALWMim65nIIS428BheYg aq6BqxDGGqORhlf7aCFGTtNaeNDsu1Tny7sNTe+TEXpKl+AwoFTJ+4+bxl50AYyp 8Niod0JGjEoxkQKsU/aScvCvEvMuPXOABfUGFtzieNpfswU2n6LHjywy+RP1mTEn aPP1arQGGGhe5b5lvolREN0VbGvymtiLr6P+qOhs76ib/dkOegq2/njBX7UlQ7Fy dIQo1A/NayUn5F7VWQKUz6ZHLX9bVZYSe2gstKpl5C8Ybwfaj/HgeT1TAdMoQ2K/ KG0HgcWwIyoIaIms+yED6WSQKJwexx4zn/t2w/Qi2eSVF6WSqNdY3rrHf3sY3luj g5wYs2AvNnGjQU6iNGs7DLwwasHgqwZcOwRIdTvY8z3UP5Wpj5y01a+dJJG378zR cZhEQUmDn21jBlJvpqSKUoNRZc1L/8uNfQLbnOMVBNOUBXIQ9Z29j2IkqGsYeTG8 uUndjyA/2SlEU29w2G6/MnJykNiW4oMxryXabXvh8dXc+SPQkUIM71ivo4y2/HgM 3XGz9l+cgJk61F0oAHtzie7MorsEGVLMA2n4TpibkUCLRIjK3e5QvEBDHZILWHPA k2b8dkF2cdu8Q4nbI3PzXUFzuq/rsBpncSvYd/zDQrEMxzhNUVmuX7B9Ws7I0P36 VKkGQqUFJNNx7LLynD7XaJ7l =nupY -----END PGP SIGNATURE----- -- Markus Probst