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([2a01:e0a:c:37e0:ced3:55bd:f454:e722]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-388c8012249sm11244064f8f.10.2024.12.17.06.46.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Dec 2024 06:46:14 -0800 (PST) Message-ID: <301714d8-0723-4881-83e8-24523c121bfe@redhat.com> Date: Tue, 17 Dec 2024 15:46:12 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 0/6] drm/log: Introduce a new boot logger to draw the kmsg on the screen To: Geert Uytterhoeven Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , John Ogness , Javier Martinez Canillas , "Guilherme G . Piccoli" , bluescreen_avenger@verizon.net, Caleb Connolly , Petr Mladek , Jani Nikula , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Linux-Renesas References: <20241204160014.1171469-1-jfalempe@redhat.com> Content-Language: en-US, fr From: Jocelyn Falempe In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 17/12/2024 15:19, Geert Uytterhoeven wrote: > Hi Jocelyn, > > On Wed, Dec 4, 2024 at 6:41 PM Jocelyn Falempe wrote: >> drm_log is a simple logger that uses the drm_client API to print the kmsg boot log on the screen. >> This is not a full replacement to fbcon, as it will only print the kmsg. >> It will never handle user input, or a terminal because this is better done in userspace. >> >> If you're curious on how it looks like, I've put a small demo here: >> https://people.redhat.com/jfalempe/drm_log/drm_log_draft_boot_v2.mp4 >> >> Design decisions: >> * It uses the drm_client API, so it should work on all drm drivers from the start. >> * It doesn't scroll the message, that way it doesn't need to redraw the whole screen for each new message. >> It also means it doesn't have to keep drawn messages in memory, to redraw them when scrolling. >> * It uses the new non-blocking console API, so it should work well with PREEMPT_RT > > I gave this a try on Koelsch (R-Car M2-W), using rcar-du. > Unfortunately I don't see any kernel messages, and my monitor complains > about no signal. Does this require special support from the driver? It doesn't require a special support from the driver. But as it is the first drm client other than fbdev emulation, I'm not surprised it's broken on some driver. I know it works on virtio-gpu, nouveau, amdgpu, and even on a OnePlus 6 (Qualcomm SDM845/freedreno), without requiring driver changes. Do you have a serial console on this device, to check if there is something in kmsg? Best regards, -- Jocelyn > > CONFIG_DRM_CLIENT=y > CONFIG_DRM_CLIENT_LIB=y > CONFIG_DRM_CLIENT_SELECTION=y > CONFIG_DRM_CLIENT_SETUP=y > CONFIG_DRM_CLIENT_LOG=y > # CONFIG_DRM_CLIENT_DEFAULT_FBDEV is not set > CONFIG_DRM_CLIENT_DEFAULT_LOG=y > CONFIG_DRM_CLIENT_DEFAULT="log" > > Switching to fbdev gives a working display, as before: > > CONFIG_DRM_CLIENT_DEFAULT_FBDEV=y > # CONFIG_DRM_CLIENT_DEFAULT_LOG is not set > CONFIG_DRM_CLIENT_DEFAULT="fbdev" > > Thanks! > > Gr{oetje,eeting}s, > > Geert >