From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout02.posteo.de (mout02.posteo.de [185.67.36.66]) (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 149FA439010 for ; Tue, 9 Jun 2026 14:56:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.67.36.66 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781017012; cv=none; b=toP9CT8//1a5xdlaGuFYLj+oaw+8b/rXwmjURUjp4V5+RZkaTPFT/iO1fpcIEoAMLLJmB3PVu9GvIg1jjEB/BnRY3twY1SkN7xPqpsAqInHuSWwJLK0fJF4ZE6+3rWHAFqulFZj/Y44ELT6N1F70U0bao8R6wMn6Ce+3PTU8t6I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781017012; c=relaxed/simple; bh=zj9Wu73Ltk1sOzoQhTIe1zSxGj1RV23OuqYlJJxGKB0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=q5FC7lsW1ZmHKPgSkbRiPNA0j5R18anw7GZv8AB/58gEKoMi6pkHE5RVV5T2WCotSg2dXZMpgMekVd7oDvK1L+2xWVfwFbYi8N3y0koArvjBKZz45Ra8md1MBSKnkUVVFqDfyIsGVBDJVaEXilMokoRC2zPkI9NY2PnaMDFzgGM= 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=aQ9CXDh1; arc=none smtp.client-ip=185.67.36.66 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="aQ9CXDh1" Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 179D7240104 for ; Tue, 9 Jun 2026 16:56:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=2017; t=1781017004; bh=TkCq9T8Scv4lUIRS90x1KMGa7qnjIlxLdGrH7gewdXk=; h=Message-ID:Subject:From:To:Cc:Date:Autocrypt:Content-Type: MIME-Version:OpenPGP:From; b=aQ9CXDh120YKFaeBkxSGZWEMwoUezQ90aFYnHQjOzWsERTlS1L8fj5zd4aVKajIhg dWq1k8TiHkEjBq+W25d7ScC8Pfh/lXcd0ux/pDemyaB93atdj2L8hNUgZ3q23W9lgP iOhFIZbpGER7850bUyj0uLY1NxopjD4v+kYtgK+eiXXxRGjuuOl3d/hIxqIXMwGITt GGnzg5uEa1nyws/xtraiyrDbbp/RBEjhxyIMncMS4ZqQCUAyUHbgOXEmueiv+nLUZT mnegwzfVMGxWZpgiQvK4QfRuEocZr3MR4RlkMtQvlaycASUAPr9hbvCasPsDxLwClD TzzvYvOwvyl3A== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4gZX6x5xJkz6txs; Tue, 9 Jun 2026 16:56:41 +0200 (CEST) Message-ID: <44a6e266e6ead9b7cbbb6c9c11f18f21a13d8c2a.camel@posteo.de> Subject: Re: [PATCH RESEND v2 1/2] serial: earlycon: add uart_clk_freq parameter From: Markus Probst To: Geert Uytterhoeven Cc: "Rafael J. Wysocki" , Len Brown , Thomas Bogendoerfer , Ard Biesheuvel , Ilias Apalodimas , Greg Kroah-Hartman , Jiri Slaby , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-efi@vger.kernel.org, linux-serial@vger.kernel.org Date: Tue, 09 Jun 2026 14:56:43 +0000 In-Reply-To: References: <20260609-acpi_spcr-v2-0-3cd9a3bda727@posteo.de> <20260609-acpi_spcr-v2-1-3cd9a3bda727@posteo.de> Autocrypt: addr=markus.probst@posteo.de; prefer-encrypt=mutual; keydata=mQINBGiDvXgBEADAXUceKafpl46S35UmDh2wRvvx+UfZbcTjeQOlSwKP7YVJ4JOZrVs93 qReNLkOWguIqPBxR9blQ4nyYrqSCV+MMw/3ifyXIm6Pw2YRUDg+WTEOjTixRCoWDgUj1nOsvJ9tVA m76Ww+/pAnepVRafMID0rqEfD9oGv1YrfpeFJhyE2zUw3SyyNLIKWD6QeLRhKQRbSnsXhGLFBXCqt 9k5JARhgQof9zvztcCVlT5KVvuyfC4H+HzeGmu9201BVyihJwKdcKPq+n/aY5FUVxNTgtI9f8wIbm fAjaoT1pjXSp+dszakA98fhONM98pOq723o/1ZGMZukyXFfsDGtA3BB79HoopHKujLGWAGskzClwT jRQxBqxh/U/lL1pc+0xPWikTNCmtziCOvv0KA0arDOMQlyFvImzX6oGVgE4ksKQYbMZ3Ikw6L1Rv1 J+FvN0aNwOKgL2ztBRYscUGcQvA0Zo1fGCAn/BLEJvQYShWKeKqjyncVGoXFsz2AcuFKe1pwETSsN 6OZncjy32e4ktgs07cWBfx0v62b8md36jau+B6RVnnodaA8++oXl3FRwiEW8XfXWIjy4umIv93tb8 8ekYsfOfWkTSewZYXGoqe4RtK80ulMHb/dh2FZQIFyRdN4HOmB4FYO5sEYFr9YjHLmDkrUgNodJCX CeMe4BO4iaxUQARAQABtCdNYXJrdXMgUHJvYnN0IDxtYXJrdXMucHJvYnN0QHBvc3Rlby5kZT6JAl QEEwEIAD4CGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AWIQSCdBjE9KxY53IwxHM0dh/4561 D0gUCaIZ9HQIZAQAKCRA0dh/4561D0pKmD/92zsCfbD+SrvBpNWtbit7J9wFBNr9qSFFm2n/65qen NNWKDrCzDsjRbALMHSO8nigMWzjofbVjj8Nf7SDcdapRjrMCnidS0DuW3pZBo6W0sZqV/fLx+AzgQ 7PAr6jtBbUoKW/GCGHLLtb6Hv+zjL17KGVO0DdQeoHEXMa48mJh8rS7VlUzVtpbxsWbb1wRZJTD88 ALDOLTWGqMbCTFDKFfGcqBLdUT13vx706Q29wrDiogmQhLGYKc6fQzpHhCLNhHTl8ZVLuKVY3wTT+ f9TzW1BDzFTAe3ZXsKhrzF+ud7vr6ff9p1Zl+Nujz94EDYHi/5Yrtp//+N/ZjDGDmqZOEA86/Gybu 6XE/v4S85ls0cAe37WTqsMCJjVRMP52r7Y1AuOONJDe3sIsDge++XFhwfGPbZwBnwd4gEVcdrKhnO ntuP9TvBMFWeTvtLqlWJUt7n8f/ELCcGoO5acai1iZ59GC81GLl2izObOLNjyv3G6hia/w50Mw9MU dAdZQ2MxM6k+x4L5XeysdcR/2AydVLtu2LGFOrKyEe0M9XmlE6OvziWXvVVwomvTN3LaNUmaINhr7 pHTFwDiZCSWKnwnvD2+jA1trKq1xKUQY1uGW9XgSj98pKyixHWoeEpydr+alSTB43c3m0351/9rYT TTi4KSk73wtapPKtaoIR3rOFHLQXbWFya3VzLnByb2JzdEBwb3N0ZW8uZGWJAlEEEwEIADsWIQSCd BjE9KxY53IwxHM0dh/4561D0gUCaIO9eAIbAwULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgAAKCR A0dh/4561D0oHZEACEmk5Ng9+OXoVxJJ+c9slBI2lYxyBO84qkWjoJ/0GpwoHk1IpyL+i+kF1Bb7y Hx9Tiz8ENYX7xIPTZzS8hXs1ksuo76FQUyD6onA/69xZIrYZ0NSA5HUo62qzzMSZL7od5e12R6OPR lR0PIuc4ecOGCEq3BLRPfZSYrL54tiase8HubXsvb6EBQ8jPI8ZUlr96ZqFEwrQZF/3ihyV6LILLk geExgwlTzo5Wv3piOXPTITBuzuFhBJqEnT25q2j8OumGQ+ri8oVeAzx24g1kc11pwpR0sowfa5MvZ WrrBcaIL7uJfR/ig7FyGnTQ1nS3btf3p0v8A3fc4eUu/K2No3l2huJp3+LHhCmpmeykOhSB63Mj3s 3Q87LD0HE0HBkTEMwp+sD97ZRpO67H5shzJRanUaDTb/mREfzpJmRT1uuec0X2zItL7a6itgMJvYI KG29aJLX3fTzzVzFGPgzVZYEdhu4y53p0qEGrrC1JtKR6DRPE1hb/OdWOkjmJ75+PPLD9U5IuRd6y sHJWsEBR1F0wkMPkEofWsvMYJzWXx/rvTWO8N4D6HigTgBXAXNgbc3IHpHlkvKoBJptv6DRVRtIrz 0G0cfBY0Sm7he4N2IYDWWdGnPBZ3rlLSdj5EiBU2YWgIgtLrb8ZNJ3ZlhYluGnBJDGRqy2jC9s1jY 66sLA9rQZMHhJTzMyIDwweGlvMzJAcG9zdGVvLmV1PokCbQQTAQgAVxYhBIJ0GMT0rFjncjDEczR2 H/jnrUPSBQJpa71VGxSAAAAAAAQADm1hbnUyLDIuNSsxLjExLDIsMgIbAwULCQgHAgIiAgYVCgkIC wIEFgIDAQIeBwIXgAAKCRA0dh/4561D0gKJD/9uOQKYlsDoQX65Gd0LiMT0C+5vXgr3VI0PHDOwcv 51fJ3A1vNyPZRFPGrz8+mDEXUQOF/INfnz5Tu1QHwf+iYcWcTGAN/FHgVR6ET6VBNU2hJaKhu+Ggo kjYyJTOvyX+3yNRUfSny0GjTjIPuPTErjqmHF+BtjXslpgwqnNMznf3lRIuUjRORupos6p3k1DndE 5vzUTmXSvMyXyOD2KhBl/kL76k0bHYyAQytZPag12pltrtFbA/r2phDGN2si8PooDT99bSTJjaM45 MTAAHbHKJfvgfK41bNFD5mMtpWpL195XRtS0Nrxdg3PaYBxN5gtTG0RyZfpYRlkdEhm+jj/8RxuSG i/qdhRdbiI7K2IELWeQVHSNDi9JabR/UzlR4NSnhfAjRIVlRM+eFbUl8XwxwVrAkojF5IraH2qRvg VCmuFsHUW07FUlrDrzpjXsD73cKppoFGDCdDR0BHJepXbFLS9+AqkT+guRJlnCTg2p+TQtnbwPgKp Vj98JixovCl99zRYTsL2bRNU5+q8iET65VMJ1ydyNanvLd5vI/NqDkXhlXLsGmdaDTtu4R21PkToX dQNGrZ91M9nlIBKw8Y7c7xZ4098qX2b8JX/CxD+gC1r4C8vuA3GkhFLx+KlkON7LyiJPkrePp6Qky jfGillcaQOqFZ3WwVqyzG1BUfTow== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-eHB9O6aTLRCXTUNZoAwj" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 OpenPGP: url=https://posteo.de/keys/markus.probst@posteo.de.asc; preference=encrypt --=-eHB9O6aTLRCXTUNZoAwj Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2026-06-09 at 08:53 +0200, Geert Uytterhoeven wrote: > Hi Markus, >=20 > On Tue, 9 Jun 2026 at 00:40, Markus Probst wrot= e: > > Add `uart_clk_freq` parameter to `setup_earlycon`. This allows the > > options string to be reused with `add_preferred_console`, while still > > allowing to set the uart clock frequency. This will be used in the > > following commit ("ACPI: SPCR: Support UART clock frequency field"). > >=20 > > No logical change intended. > >=20 > > Signed-off-by: Markus Probst >=20 > > --- a/drivers/tty/serial/earlycon.c > > +++ b/drivers/tty/serial/earlycon.c > > @@ -135,11 +135,14 @@ static int __init parse_options(struct earlycon_d= evice *device, char *options) > > return 0; > > } > >=20 > > -static int __init register_earlycon(char *buf, const struct earlycon_i= d *match) > > +static int __init register_earlycon(char *buf, unsigned int uart_clk_f= req, > > + const struct earlycon_id *match) > > { > > int err; > > struct uart_port *port =3D &early_console_dev.port; > >=20 > > + port->uartclk =3D uart_clk_freq; >=20 > Who is actually consuming this value? I think primarily init_port in drivers/tty/serial/8250/8250_early.c. > Earlycon typically works with the serial console, as configured before > Linux boot by the firmware. Thats defined in the SPCR table. If "Configured Baud Rate" is set to 0, it will use it as is [1]. If not, it will configure it. Thanks - Markus Probst [1]https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/seria= l-port-console-redirection-table > The Microsoft doc referenced in patch 2 seem to agree with that: >=20 > "On a system where the BIOS or system firmware uses the serial > port for console input/output, this table should be used to convey > information about the settings, to ensure a seamless transition > between the firmware console output and Windows EMS output." >=20 > > + > > /* On parsing error, pass the options buf to the setup function= */ > > if (buf && !parse_options(&early_console_dev, buf)) > > buf =3D NULL; >=20 > Gr{oetje,eeting}s, >=20 > Geert --=-eHB9O6aTLRCXTUNZoAwj Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQJPBAABCAA5FiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IFAmooKakbFIAAAAAABAAO bWFudTIsMi41KzEuMTIsMiwyAAoJEDR2H/jnrUPSTOQP/3lOjjeD4rihyrtDkGdA vD1xzqthwYFbU2fa+qQ1yTgmbp+z5+h7rcbx8T5S2Y7HkuLbilRDe7Q8SGJocpIg T9085pQlUhA9lCVY+5s0oXqUp+8rSaUSwXYp+MJH8ZXSwPVdr4kDJoAOs8t+PUt0 i9EGA6/6vW2ccRJwYLaCDxmJowfeQZJJG0cjG5ZWLPj2pOOwbXc3Tm8ZWrtfzADd sS9irtr/CjlO4L6CBUZ2qEIAT1QylOZTOat/B0Xw0VmupSK0ib31FfEzZsxOoCnR 0Dx16p95q+DMLIKa7zgAhrUyvrJjxI2pDpALJfXrbwhjMbjhB+d6lIfL0kEJF8F3 JJg5y5X9ixNdfWomlDFFn6IyLzcuTqrymCLcW14h/lIuGlAv4CDg3OS/i4T+wBW+ raRTVeakyeBUxxwS499UN0EmcFuxI6CuYiEd9it6kbBJU/4w4mfsbB5Lr2eoWh3m OSuACvoFlS84V3+SQbbziaTFRo+eLtyNfHHpKNM4d2n2Pdn5tWdoXKkoGacl5hhJ maQmavGZGDX2pWcpdmoB8fDys9gHkhVdMPUPWSdA8KQ3YG01u2gF98UeClteWJOW tWr4TpLpsrH/5rzFgz4usuMXaetG7wyeMdjVq+7LjG1pGjbeEifYux73o2CxjPkg 6DHab0pVROd5cS1MZIXwtSA/ =g1gl -----END PGP SIGNATURE----- --=-eHB9O6aTLRCXTUNZoAwj--