From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 22DE7CAC5B9 for ; Fri, 26 Sep 2025 10:37:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=WNkD1K2RBkYayp44h1XfQoipSL3WE30xESe/2y5Vgrg=; b=mLHxkyz+3JOk/s3nTfiU4adkus 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Content-Transfer-Encoding:cc:content-transfer-encoding: content-type:date:from:message-id:mime-version:reply-to:subject: to; b=oDWdEYQ/1UPJoIhl/vVEcLvcfPLHC/CbkOCX1I0PKfVZshT0sn8CQEVuBaYd0WS9 IpYXFjAVQXkkzqpN/93PPuVXVOfF1Lncm6QHfoq82E3B1Qw9driaZud5cSGNY2PoO /R/G6PldwTuRcx8ej07xRxvaOJ/OAdICnJ+MboOXTj9lMszxqJ4YLnBheOTW1zOtV A6KhnEYC9lSMIUlRwSIn/C2rw1G9UdVyGYyv4yMH4h59wj4W8bVniXf1PE3+9qRq0 zH+rg3nQPJCFxwWeeq6Mxv4+m/6B8Pg1K+q2RNnVoLrgBrOPO75Dob1MVqcgLiSYM MHuvL1Evo1wsFq6Rjw== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from [192.168.1.105] ([79.235.128.112]) by mail.gmx.net (mrgmx104 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MCKBm-1vAJIR2JOM-006muJ; Fri, 26 Sep 2025 12:36:49 +0200 Message-ID: Date: Fri, 26 Sep 2025 12:36:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] clk: bcm: rpi: Turn firmware clock on/off when preparing/unpreparing To: Marek Szyprowski , =?UTF-8?Q?Ma=C3=ADra_Canal?= , Michael Turquette , Stephen Boyd , Nicolas Saenz Julienne , Florian Fainelli , Maxime Ripard , Melissa Wen , Iago Toral Quiroga , Dom Cobley , Dave Stevenson , Philipp Zabel Cc: linux-clk@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org, Broadcom internal kernel review list , kernel-dev@igalia.com References: <20250731-v3d-power-management-v2-0-032d56b01964@igalia.com> <20250731-v3d-power-management-v2-2-032d56b01964@igalia.com> <727aa0c8-2981-4662-adf3-69cac2da956d@samsung.com> <2b1537c1-93e4-4c6c-8554-a2d877759201@gmx.net> <1e5d1625-1326-4565-8407-71a58a91d230@samsung.com> Content-Language: en-US From: Stefan Wahren Autocrypt: addr=wahrenst@gmx.net; keydata= xjMEZ1dOJBYJKwYBBAHaRw8BAQdA7H2MMG3q8FV7kAPko5vOAeaa4UA1I0hMgga1j5iYTTvN IFN0ZWZhbiBXYWhyZW4gPHdhaHJlbnN0QGdteC5uZXQ+wo8EExYIADcWIQT3FXg+ApsOhPDN NNFuwvLLwiAwigUCZ1dOJAUJB4TOAAIbAwQLCQgHBRUICQoLBRYCAwEAAAoJEG7C8svCIDCK 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i0uWWkJYCxO33G+8PwF9e4QwdWSQnCGMHm0Pe5ksV2AGq1jj1ep9qnvHmta6AgLUO1DmCKnCa qz1rv9VFhi1wO6r20ahK1dDR6WTRpowq4W1Pdb1dQtg9G04bxJ2yUiMnUgIWgeSHzao2Bqn81 V2yFmDWYgzqTnmAgOlfVDKFYQ7lVvYqBhCrwEflwx2Oao/CsSF2jERBrDWGvOJRGFrCJMBO8N FTbwgfcHLE/CjzVDtOTDaKf7VUEmQ4Jziht24DwmJyRTa00 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250926_033733_992115_931702CD X-CRM114-Status: GOOD ( 21.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Marek, Am 26.09.25 um 09:27 schrieb Marek Szyprowski: > On 25.09.2025 18:48, Stefan Wahren wrote: >> Am 25.09.25 um 09:57 schrieb Marek Szyprowski: >>> On 31.07.2025 23:06, Ma=C3=ADra Canal wrote: >>>> Currently, when we prepare or unprepare RPi's clocks, we don't actual= ly >>>> enable/disable the firmware clock. This means that >>>> `clk_disable_unprepare()` doesn't actually change the clock state at >>>> all, nor does it lowers the clock rate. >>>> >>>> >From the Mailbox Property Interface documentation [1], we can see th= at >>>> we should use `RPI_FIRMWARE_SET_CLOCK_STATE` to set the clock state >>>> off/on. Therefore, use `RPI_FIRMWARE_SET_CLOCK_STATE` to create a >>>> prepare and an unprepare hook for RPi's firmware clock. >>>> >>>> As now the clocks are actually turned off, some of them are now marke= d >>>> CLK_IS_CRITICAL, as those are required to be on during the whole syst= em >>>> operation. >>>> >>>> Link:https://github.com/raspberrypi/firmware/wiki/Mailbox-property-in= terface >>>> [1] >>>> Signed-off-by: Ma=C3=ADra Canal >>>> >>>> --- >>>> >>>> About the pixel clock: currently, if we actually disable the pixel >>>> clock during a hotplug, the system will crash. This happens in the >>>> RPi 4. >>>> >>>> The crash happens after we disabled the CRTC (thus, the pixel clock), >>>> but before the end of atomic commit tail. As vc4's pixel valve doesn'= t >>>> directly hold a reference to its clock =E2=80=93 we use the HDMI enco= der to >>>> manage the pixel clock =E2=80=93 I believe we might be disabling the = clock >>>> before we should. >>>> >>>> After this investigation, I decided to keep things as they current ar= e: >>>> the pixel clock is never disabled, as fixing it would go out of >>>> the scope of this series. >>>> --- >>>> =C2=A0=C2=A0 drivers/clk/bcm/clk-raspberrypi.c | 56 >>>> ++++++++++++++++++++++++++++++++++++++- >>>> =C2=A0=C2=A0 1 file changed, 55 insertions(+), 1 deletion(-) >>> This patch landed recently in linux-next as commit 919d6924ae9b ("clk: >>> bcm: rpi: Turn firmware clock on/off when preparing/unpreparing"). In = my >>> tests I found that it breaks booting of RaspberryPi3B+ board in ARM >>> 32bit mode. Surprisingly the same board in ARM 64bit mode correctly >>> boots a kernel compiled from the same source. The RPi3B+ board freezes >>> after loading the DRM modules (kernel compiled from >>> arm/multi_v7_defconfig): >> thanks for spotting and bisecting this. Sorry, I only reviewed the >> changes and didn't had the time to test any affected board. >> >> I was able to reproduce this issue and the following workaround avoid >> the hang in my case: >> >> diff --git a/drivers/clk/bcm/clk-raspberrypi.c >> b/drivers/clk/bcm/clk-raspberrypi.c >> index 1a9162f0ae31..94fd4f6e2837 100644 >> --- a/drivers/clk/bcm/clk-raspberrypi.c >> +++ b/drivers/clk/bcm/clk-raspberrypi.c >> @@ -137,6 +137,7 @@ raspberrypi_clk_variants[RPI_FIRMWARE_NUM_CLK_ID] = =3D { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [RPI_FIRMWARE_V3D_CLK_ID] = =3D { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 .export =3D true, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 .maximize =3D true, >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 .flags =3D CLK_IS_CRITICAL, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 }, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [RPI_FIRMWARE_PIXEL_CLK_ID]= =3D { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 .export =3D true, >> > Right, this fixes (frankly speaking 'hides') the issue. Feel free to add= : > > Reported-by: Marek Szyprowski > Tested-by: Marek Szyprowski > AFAIK the offending clock change isn't in the downstream kernel, so I=20 like to see the opinion of Mar=C3=ADa and the Raspberry Pi people first. Currently I know that in the error case the following clocks are=20 disabled during boot of Raspberry Pi 3B+: fw-clk-vec fw-clk-isp fw-clk-v3d So it's very likely that the vc4 drivers tries to access the register=20 after the these clocks has been disabled and then the system freeze. The= =20 workaround above was just a wild guess, so currently I don't know why=20 this change avoid the freeze. Best regards