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([2400:4050:c360:8200:8ae8:3c4:c0da:7419]) by smtp.gmail.com with ESMTPSA id b1-20020a63d801000000b0046ff7db0984sm2842628pgh.72.2022.12.01.10.14.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Dec 2022 10:14:45 -0800 (PST) Message-ID: <18c884cb-dd73-09eb-65da-604cf45cb1b4@daynix.com> Date: Fri, 2 Dec 2022 03:14:41 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH] arch: arm64: dts: apple: Remove stdout-path Content-Language: en-US To: Hector Martin , Mark Kettenis Cc: linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, asahi@lists.linux.dev, krzysztof.kozlowski+dt@linaro.org, robh+dt@kernel.org, alyssa@rosenzweig.io, sven@svenpeter.dev References: <20221201103651.27807-1-akihiko.odaki@daynix.com> <877czb42wk.fsf@bloch.sibelius.xs4all.nl> <8b3c4fe0-4a81-ba47-2f01-3686cfdbd519@daynix.com> <647b6572-e5d1-d243-283e-616cef15a1f5@marcan.st> From: Akihiko Odaki In-Reply-To: <647b6572-e5d1-d243-283e-616cef15a1f5@marcan.st> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/12/02 2:46, Hector Martin wrote: > On 02/12/2022 01.38, Akihiko Odaki wrote: >> >> In contrary, if you boot the kernel without the hypervisor >> >> feature and this change, you will completely lose the console. >> > >> > How so? The console goes to both places with stdout-path set to serial0. >> > What it *does* change is where input is accepted prior to getty startup >> > (which is why u-boot specifically conditions this on keyboard presence, >> > modulo the USB issue - because if you *don't* have a keyboard then tty >> > keyboard input is useless). But if you're booting kernels without u-boot >> > along the way, you're probably doing it from the hypervisor or linux.py >> > anyway, especially if you plan to do something like "init=/bin/sh", >> > because without u-boot (+ optionally some EFI loader) there is no way of >> > editing command line arguments at boot time stand-alone. >> >> Well, that is not exactly the behavior I saw. In my case, if stdout-path >> is pointed to serial, there is no output on the framebuffer, and it just >> printed "_". >> >> It looks like the kernel only outputs to either of serial and >> framebuffer, not both. > > That is not what I've seen in all of my hypervisor runs since the dawn > of time. You get log output on both. > >> What I experienced is that when I directly booted the kernel from m1n1 >> without hypervisor, it showed no output to the display even though the >> same kernel worked with U-Boot. While I could tell it used wrong console >> by running the hypervisor, I wondered why it behaves differently without >> U-Boot, and found the aforementioned U-Boot change, coming up with this >> patch. > > Then it sounds like something else is different about our setups, > because I've booted the kernel from linux.py hundreds of times and I get > output on both. Looking through the console code, the VT console gets > added and enabled really early, and the subsequent serial console > registration later does not disable it. > > Look for "console: colour dummy device 80x25". It should be immediately > followed by "printk: console [tty0] enabled", and this should all come > well before the ttySAC0 serial stuff shows up. > > - Hector I think I understand the situation now. By "console", I was meaning the input and output of init, but I failed to clarify that and you thought it referring to kernel message output. I saw no messages earlier than init because my kernel command line has loglevel=3. Regards, Akihiko Odaki