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Tue, 20 Oct 2026 12:17:02 -0700 (PDT) Received: from localhost ([200.10.125.114]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-19035926035sm587423c88.1.2026.10.20.12.16.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Oct 2026 12:17:02 -0700 (PDT) X-Archived-By: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 20 Oct 2026 16:16:58 -0300 Message-Id: Cc: "Florian Fainelli" , "Broadcom internal kernel review list" , "Jai Luthra" , "Greg Kroah-Hartman" , "Stefan Wahren" , "Phil Elwell" , "Laurent Pinchart" , "Umang Jain" , "Kees Cook" , , , , , Subject: Re: [PATCH] platform/raspberrypi: vchiq: register bus at subsys_initcall From: "Gaston Gonzalez" To: "Martin Wetterwald" X-Mailer: aerc 0.20.0 References: <20261013131435.1454019-1-martin@wetterwald.eu> In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261020_121704_278092_07559EAB X-CRM114-Status: GOOD ( 42.12 ) X-Spam-Score: -2.1 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon Oct 19, 2026 at 9:26 AM -03, Martin Wetterwald wrote: > On Sun, Oct 18, 2026 at 9:53=E2=80=AFPM Gaston Gonzalez wrote: > >> Running 'speaker-test -t wav -D plughw:1,0 -c 2' crash the system, so >> thinks seem not to be working with that interface. >> >> Im trying to debug what happens in that condition; I will need a couple >> of days I guess. So far, this is what I could check. >> >> Any feedback on the test or debugging would be appreciated. > > Hi Gaston, > Thanks for digging into this. > Hi Martin, > The patch only changes when the VCHIQ bus and driver are registered durin= g > boot. So it's enough to check these two cases to validate the patch: > - without my patch: dmesg shows the "unable to register with bus_type > 'vchiq-bus'" error, and bcm2835_hdmi is absent from /proc/asound/cards. > - with my patch: the error is gone and bcm2835_hdmi is present in > /proc/asound/cards. > Understood. Of the two cases, the second one is already tested if I'm not mistaken. I will check the 'without your patch' case first, and then I'll rerun the test with your patch. > (Since the Pi Zero has no Headphones jack, you need to test both cases wi= th > snd_bcm2835.enable_hdmi=3D1 in the command line. Otherwise the card never= shows > up, even when everything works.) > > Could you check these two cases? > Yes, will do. > > Testing that you can hear the sound going through bcm2835-audio is a full > functional test that goes even further than the patch: it does not only t= est > bus registration but also that the audio driver is working. > > On my side, without vc4-drm, I can successfully hear sound through both b= cm2835 > Headphones and bcm2835 HDMI: > > # aplay -l > **** List of PLAYBACK Hardware Devices **** > card 0: HDMI [bcm2835 HDMI], device 0: bcm2835 HDMI [bcm2835 HDMI] > [...] > card 0: HDMI [bcm2835 HDMI], device 1: IEC958 [IEC958] > [...] > card 1: Headphones [bcm2835 Headphones], device 0: bcm2835 > Headphones [bcm2835 Headphones] > [...] > > # speaker-test -D plughw:0,0 # (HDMI) > > # speaker-test -D plughw:1,0 # (Headphones, not on the Pi Zero) > > > If you still want to output sound through bcm2835_hdmi (optional): > > There can only be one owner of the HDMI port: either the firmware or the > kernel. > When the Raspberry Pi boots, the firmware first owns the HDMI and display= s a > rainbow splash. Then it launches Linux. > > There are 2 ways for the kernel to deal with the video output: > > 1) With vc4-drm (CONFIG_DRM_VC4), the kernel takes over the HDMI controll= er > from the firmware and handles everything itself (this is your case). > 2) With simple-framebuffer (CONFIG_DRM_SIMPLEDRM or CONFIG_FB_SIMPLE), th= e > kernel leaves the HDMI to the firmware and just writes pixels to a > memory area > (the framebuffer) set up by the firmware. > > I get a similar problem on my side when sending sound through bcm2835_hdm= i with > vc4-drm loaded: my screen shuts down (but the kernel is still alive). > It most likely comes from the firmware and the kernel both trying to driv= e the > same HDMI port: with vc4-drm, the kernel owns the HDMI controller, and th= e > firmware (which bcm2835-audio talks to through VCHIQ) is not supposed to = touch > it. > Ah ok, I did not know that. Thank you for the explanation. > A simple way to output sound through bcm2835_hdmi is to not use the vc4-d= rm > driver at all, and use simple-framebuffer if you still want a display. > > To remove vc4-drm: > - Do not compile the driver into the kernel (CONFIG_DRM_VC4=3Dn) or black= list the > module. > - Remove any vc4 overlay in config.txt file (e.g. remove dtoverlay=3Dvc4-= kms-v3d). > > To enable simple-framebuffer, use one of the two configs: > > CONFIG_DRM=3Dy > CONFIG_DRM_SIMPLEDRM=3Dy > CONFIG_DRM_FBDEV_EMULATION=3Dy > CONFIG_FRAMEBUFFER_CONSOLE=3Dy > > or, the older way: > > CONFIG_FB=3Dy > CONFIG_FB_SIMPLE=3Dy > CONFIG_FRAMEBUFFER_CONSOLE=3Dy > > (FRAMEBUFFER_CONSOLE=3Dy, and DRM_FBDEV_EMULATION in the DRM case, are on= ly > needed to see the boot messages on the screen, with console=3Dtty1 on the= command > line.) > > If you have remote access to your Pi Zero (either through network+SSH or > through serial console), you actually don't even need the simple-framebuf= fer: > you can just remove vc4-drm, and let the firmware display its rainbow spl= ash on > the HDMI port. > Then you can login to your Pi Zero through SSH for example and launch > speaker-test. > As long as the HDMI video output is active, it's enough for the sound to = be > able to go through, even if the image was not drawn by Linux. > > But again, this full functional test is optional. > Ok, I=E2=80=99ll test the patch first with the current configuration, then with simple-framebuffer enabled in a second step. Regards, Gaston > Regards, > Martin