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 4B26E1A83E1; Tue, 7 Jan 2025 23:07:43 +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=1736291264; cv=none; b=O6kXvaqMt4wKPyvhcQHG1Y9BDZ59yWabkgs+QZhYReftofsgRTAXwy0Irj7ELleSDBdjX6O3b4hO62iVgNuo/TrO92y1JHCqYxgHlSEJFzVC3CVn8sFlNyAJojGO6lFnEaVMwjWzZwAa8ED/3voSnbrjBPcMVsHahHqpPBX/If4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736291264; c=relaxed/simple; bh=qCOsJ/wKHOi3SAkDBRYfIUDYbFC/ozgvyeH4knr/FXA=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=qtT/qwq4XH3XxRwzbMkwAk2tmVSGqdRK/MVISVA54utImG5rd9HxRZLMo32ahHLb5kmikDXceU64aDZKTRhUOJoFojw4dLuqMjnosX1+1Xk5i7eSvq4bO1SXBUDOfs+HNC2CBVwHZ7XGttTx4qnbUZX5ClMOjiY3Clb6fjTIc+A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Lbv4lvYy; 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="Lbv4lvYy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99020C4CEDF; Tue, 7 Jan 2025 23:07:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736291263; bh=qCOsJ/wKHOi3SAkDBRYfIUDYbFC/ozgvyeH4knr/FXA=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=Lbv4lvYyU3hdnUYszWRuxX22YRUZGI6KXGwtAZ0QayGT7PHOTKKa0IPoqG2EmSchl 3Pk0IAVh3ynu5a8qsvbVQP++4PaPE443CgJi9TVTTWGQzlKlrGgvo4osLY/vyk+2Ae s5krWEJBDP+TCUCS1YTlph1APAIQQ61PXi4BCdyPtzWJzAvC2Uta6zK6MzxXxwCr6C EAPGePwBBXgrMCetp9aLHjjMHQgqLXnt1AGjcrr9nInknI5OvElB86o160HIRO2cA/ Tngd46xXYTVXCCH2EcaYrvWGXqVztxxk+xxl5jSodUU/D0RvS8VeWoGF49vYkMeQVg 1mvrlRa1FVllA== Date: Tue, 7 Jan 2025 17:07:42 -0600 From: Bjorn Helgaas To: AngeloGioacchino Del Regno Cc: Jianjun Wang =?utf-8?B?KOeOi+W7uuWGmyk=?= , "manivannan.sadhasivam@linaro.org" , "conor+dt@kernel.org" , "robh@kernel.org" , "kw@linux.com" , "bhelgaas@google.com" , "matthias.bgg@gmail.com" , "krzk+dt@kernel.org" , "lpieralisi@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , Ryder Lee , "devicetree@vger.kernel.org" , Xavier Chang =?utf-8?B?KOW8teeNu+aWhyk=?= Subject: Re: [PATCH 3/5] PCI: mediatek-gen3: Disable ASPM L0s Message-ID: <20250107230742.GA189563@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1a48feae-f55f-4df8-b165-84c1cb2f6658@collabora.com> On Tue, Jan 07, 2025 at 12:44:43PM +0100, AngeloGioacchino Del Regno wrote: > Il 07/01/25 03:18, Jianjun Wang (王建军) ha scritto: > > On Fri, 2025-01-03 at 10:16 +0100, AngeloGioacchino Del Regno wrote: > > > Il 03/01/25 07:00, Jianjun Wang ha scritto: > > > > Disable ASPM L0s support because it does not significantly save > > > > power > > > > but impacts performance. > > > > > > That may be a good idea but, without numbers to support your > > > statement, it's a bit > > > difficult to say. > > > > > > How much power does ASPM L0s save on MediaTek SoCs, in microwatts? > > > How is the performance impacted, and on which specific device(s) on > > > the PCIe bus? > > > > It's hard to tell the exact number because it is difficult to measure, > > and the number of entries into the L0s state may vary even in the same > > test scenario. > > > > However, we have encountered some compatibility issues when connected > > with some PCIe EPs, and disabling the L0s can fix it. I think disabling > > L0s might be the better way, since we usually use L1ss for power-saving > > when the link is idle. > > To actually decide, we should know what's actually broken, then. > > Is the MediaTek controller broken, or is the device broken? > So, is it a MTK quirk, or a device quirk? > > If the problem is actually device-related, then this should be handled as > a device-specific quirk, as not just MediaTek platforms would be affected > by compatibility issues. > > If the MediaTek PCIe controller is at fault, instead, I agree about just > disabling L0s at the controller level - but then this shall be mentioned > in the commit message, and should have a Fixes tag as well. 100% agreed, sorry for repeating what you just said before I finished reading the thread! Bjorn