From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 29904246787; Thu, 19 Jun 2025 19:57:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750363031; cv=none; b=QKQIum5L7T1sSmNaGqOU07TMnF25sAExAyJ+vjemf/7+9gy3+vsetimcrrAQoxDyX/ml9JR4XSAKJWqkVJmXQieOMJDHF0ka1WeQo7V2WzePjrl0/DEdQG2w2uYxcw5hcAcjr01hAlU66k3rTFKmm0S667DFjj8t6jUq7kcCyGE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750363031; c=relaxed/simple; bh=ibWzxSUcPdGpnUffjV9oSw3Mgv/hOA1CQ+xqnIiMa/A=; h=Content-Type:MIME-Version:In-Reply-To:References:Subject:From:Cc: To:Date:Message-ID; b=cX9UJ07YH+reXPk5AEboCfsH5wr7R6O3S1TQ+SQUk2e8kKUX9jOY03BYBwitVjpwwsVmKyv1kch9+vMOat0Ay17G70WZBqcqwnIs7zO6nA9tZqL90CjQBkDJhshyEklH7FAH1dgsX7/0j81aCoqjrQJfsbEiS8cW6o8Yk3dfaTs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g7jPXHyk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="g7jPXHyk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88289C4CEEE; Thu, 19 Jun 2025 19:57:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750363030; bh=ibWzxSUcPdGpnUffjV9oSw3Mgv/hOA1CQ+xqnIiMa/A=; h=In-Reply-To:References:Subject:From:Cc:To:Date:From; b=g7jPXHykDJy4xCaKiVKrMn/tusr/gawzeCFHZsc615sMC0WdBFcbe0OEa/N2TwOU/ 8cCrH8oAjJGS25DqiggSTogcvqHVrqG3TX2l/vfNry2tD22ByRLNj/3wo7br5XAs27 LbzPlS6RZBVgJ/aeKgQXXsKfz5ghIbHtulZDVyt/l4IVyTkWIXfwHi49CqD++c/KEm ILBSgtmDHnclzgrdvUrpKTudmpzrPXV24U7LJ6smnPjOzyKzH1/Dine16SudrOKCaf xFTD3rTebrWRDONzLhLiL2HHOSafqYpf6frftNckvxweqvVKY+Ee52uOZd32SnAOuF 0X3uMOw0XlNdg== Content-Type: text/plain; charset="utf-8" Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable In-Reply-To: <20250618-rust-next-pwm-working-fan-for-sending-v4-5-a6a28f2b6d8a@samsung.com> References: <20250618-rust-next-pwm-working-fan-for-sending-v4-0-a6a28f2b6d8a@samsung.com> <20250618-rust-next-pwm-working-fan-for-sending-v4-5-a6a28f2b6d8a@samsung.com> Subject: Re: [PATCH v4 5/9] clk: thead: Mark essential bus clocks as CLK_IGNORE_UNUSED From: Stephen Boyd Cc: linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-clk@vger.kernel.org To: Albert Ou , Alex Gaynor , Alexandre Ghiti , Alice Ryhl , Andreas Hindborg , Benno Lossin , =?utf-8?q?Bj=C3=B6rn?= Roy Baron , Boqun Feng , Conor Dooley , Danilo Krummrich , Drew Fustini , Fu Wei , Gary Guo , Guo Ren , Krzysztof Kozlowski , Marek Szyprowski , Michael Turquette , Michal Wilczynski , Miguel Ojeda , Palmer Dabbelt , Paul Walmsley , Rob Herring , Trevor Gross , Uwe =?utf-8?q?Kleine-K=C3=B6nig?= Date: Thu, 19 Jun 2025 12:57:09 -0700 Message-ID: <175036302986.4372.15656426260486761164@lazor> User-Agent: alot/0.11 Quoting Michal Wilczynski (2025-06-18 05:27:38) > Probing peripherals in the AON and PERI domains, such as the PVT thermal > sensor and the PWM controller, can lead to boot hangs or unresponsive > devices on the LPi4A board. The root cause is that their parent bus > clocks ('CLK_CPU2AON_X2H' and the 'CLK_PERISYS_APB' clocks) are > automatically gated by the kernel's power-saving mechanisms when the bus > is perceived as idle. >=20 > Alternative solutions were investigated, including modeling the parent > bus in the Device Tree with 'simple-pm-bus' or refactoring the clock > driver's parentage. The 'simple-pm-bus' approach is not viable due to > the lack of defined bus address ranges in the hardware manual and its > creation of improper dependencies on the 'pm_runtime' API for consumer > drivers. >=20 > Therefore, applying the'`CLK_IGNORE_UNUSED' flag directly to the > essential bus clocks is the most direct and targeted fix. This prevents > the kernel from auto-gating these buses and ensures peripherals remain > accessible. >=20 > This change fixes the boot hang associated with the PVT sensor and > resolves the functional issues with the PWM controller. >=20 > Link: https://lore.kernel.org/all/9e8a12db-236d-474c-b110-b3be96edf057@sa= msung.com/ [1] >=20 > Reviewed-by: Drew Fustini > Signed-off-by: Michal Wilczynski > --- Acked-by: Stephen Boyd