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Fri, 17 Apr 2026 10:24:24 -0700 (PDT) Received: from smtpclient.apple ([197.250.227.196]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ba45503c435sm75465166b.43.2026.04.17.10.24.19 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 17 Apr 2026 10:24:23 -0700 (PDT) Content-Type: multipart/signed; boundary="Apple-Mail=_6363C69E-ACB3-474B-9473-521CD530D032"; protocol="application/pgp-signature"; micalg=pgp-sha256 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.500.181\)) Subject: Re: [PATCH v4 7/8] ARM: dts: Declare UART1 on zx297520v3 boards From: =?utf-8?Q?Stefan_D=C3=B6singer?= In-Reply-To: <0d80dcbe-cb46-45e5-821a-de5299d6a663@app.fastmail.com> Date: Fri, 17 Apr 2026 20:24:05 +0300 Cc: Jonathan Corbet , Shuah Khan , Russell King , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Krzysztof Kozlowski , Alexandre Belloni , Linus Walleij , Drew Fustini , Greg Kroah-Hartman , Jiri Slaby , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, soc@lists.linux.dev, linux-serial@vger.kernel.org Message-Id: References: <20260416-send-v4-0-e19d02b944ec@gmail.com> <20260416-send-v4-7-e19d02b944ec@gmail.com> <0d80dcbe-cb46-45e5-821a-de5299d6a663@app.fastmail.com> To: Arnd Bergmann X-Mailer: Apple Mail (2.3864.500.181) --Apple-Mail=_6363C69E-ACB3-474B-9473-521CD530D032 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 Hi Arnd, Thanks for your comments. > Am 17.04.2026 um 11:59 schrieb Arnd Bergmann : >=20 > On Thu, Apr 16, 2026, at 22:19, Stefan D=C3=B6singer wrote: >>=20 >> The reason why I add the serial1=3Duart1 alias is to keep = console=3DttyAMA1 >> stable regardless of the other enabled UARTs. UART0, as the name >> implies, has a lower MMIO address, but uart1 is the one that usually = has >> the boot output and console. >=20 > I'm not sure I'm following here. You generally want to either make > sure the alias matches whatever number is printed on the product > if there are multiple numbered ports, or you just use 'serial0' > as the only alias if there is only one port. Not all boards have their uart pins labeled, but those that do have the = pins that connect to the UART at 0x01408000 named UART1RX/UART1TX. Most = boards have only one though. I have seen a picture of only one that has = UART0 and UART1. I could not test that board myself yet. My original reason is one of developer convenience: If I have uart0=3Dserial@131000{ reg =3D <0x00131000 0x1000>; ... status =3D "disabled"; }; uart1=3Dserial@1408000{ reg =3D <0x01408000 0x1000>; ... status =3D "okay"; }; cmdline=3D"... console=3DttyAMA{0/1} ..." changing uart0.status between disabled and okay (e.g. to experiment with = uart0 and pinctrl) required changing the command line to match. I found = that pretty annoying and the aliases seemed like the best way to avoid = this. Either way I am open to do whatever. I can keep the current naming for = the reasons stated above, I can name serial@1408000 "uart0" and leave = the others without an alias or I can drop the alias altogether. > Either way, the alias should go into the board specific file, not > the general SoC file, as a board might be using a different > set of UARTs. That works for me, I'll move them. The aliases will most likely be the = same for all boards based on this chipset, meaning duplicate code, but = matching the alias to the board labels makes sense to me. > Since you know the addresses of the other uart instances, I would > suggest you add all of them at the same time. Will do. I'll hold off for a bit before I resend the patches to see if some other = comments come up. Cheers, Stefan= --Apple-Mail=_6363C69E-ACB3-474B-9473-521CD530D032 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEQxb0tqoFWyeVMl1sPRO8yFRPGiIFAmnibLUACgkQPRO8yFRP GiIKTQ/+NaGjhii1hGtfVI27m5B7xvrO45mnvMkcV0ceIDc63OvWS4qRsBlOJnwF 9pjaplL2Kbm4sf/uPfQnAE0BviBly1d/14riJjJmEr4G4re2+Q/c9BeCxazBDbDJ tjODl+Ajwiu273EcwTN4ZU28p/80oJjmuEEAHsL8crw7d8rhnOjrwY/Ige9HgcBl BYlJRjunX6SxHxGNH/eEfrwrABGjHVD1ya8YjQ9NIZnkEEub9lRZO4v3gr3mU0F1 tjATbZV1BL1SQ3/Zld3BNzYkj7JzCmiEH601T3RZittY4yZBDefYMFantWcrq8Ug nVM3or6OxSiKoLQ6vak5XVW9ks1iX1k+jU19AUN71/VIvWQ+zTVnO9c1wJae/eEe SMeyP/Kt4bOGDi1Bq22aD+nv2lJ8wo/4l3k9vDv8vJDECg6UxjLFgYPbtJyEV/wr mTaODzo1XDfo4PXQD5x0bpgYrguK4X0wVM5Yu/+x/kZLKrm+TWfXN4exCwO6WJPW sZ7mj6ksI03MTxB5XpBKeoaruf//hQe3lhLDJ837SaDq8xCekCsldXyMop/qQ92a HBwMG6hD3kLzxRjClYksypijVruKHNcHshp0imqt1Hhs5wXNbaEsTQOqRUgSWj08 Yb2Veu9YNoQcnrIK0Kh0YtoHMDb29uagvWkRg63fyD40m56GPyA= =CzCY -----END PGP SIGNATURE----- --Apple-Mail=_6363C69E-ACB3-474B-9473-521CD530D032--