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 67B30219F2; Wed, 4 Oct 2023 21:59:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IQXXKp3m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0ACD8C433C8; Wed, 4 Oct 2023 21:59:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696456792; bh=h1wuJu7EQsw0ISUx0TDepOY/LS54P4l5en5rkpEd2fY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=IQXXKp3mHSs7C3RpBvqk6NjjA3omclpdvfBr+th98AGd/jJHwr+SNYt3DrQA/tTC6 CGVXbkPAeLNP+ogRrvru18i0GSibBl+w7HXMap5DQDuOrYmLdw+Tx1W6/MbCpIrsYq uQ3amhujSUY0KGp2MM38dxsXREQ33YXtIE15pnkYiOSaXPIiIUmxtBEpzyfZ9vgDDo bI7OyMePLY5CWCjr27kEoifclTlu1G2sjnuJ22oAvnoWRy9zz4MvD4Uf4V77e1j84o PZj8x033qUbHukwEnp7u6/RJOHhxm8BSYTwVY5olkQb+SrKjjXJGu8bwuLwx25JHMi kQ8hdjMEwCLSQ== Date: Wed, 4 Oct 2023 14:59:51 -0700 From: Jakub Kicinski To: Shenwei Wang Cc: "David S. Miller" , Eric Dumazet , Paolo Abeni , Shawn Guo , Sascha Hauer , Maxime Coquelin , Alexandre Torgue , Jose Abreu , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, imx@lists.linux.dev, Mario Castaneda Subject: Re: [PATCH net] net: stmmac: dwmac-imx: request high frequency mode Message-ID: <20231004145951.570a8ce4@kernel.org> In-Reply-To: <20231004195442.414766-1-shenwei.wang@nxp.com> References: <20231004195442.414766-1-shenwei.wang@nxp.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 4 Oct 2023 14:54:42 -0500 Shenwei Wang wrote: > Some i.MX SoCs like the i.mx8mq support adjusting the frequency of the > DDR, AHB, and AXI buses based on system loading. If the dwmac interface > in the driver does not request a HIGH frequency, it can significantly > degrade performance when the system switches to a lower frequency to > conserve power. > > For example, on an i.MX8MQ EVK board, the throughput dropped to around > 100Mbit/s on a 1Gbit connection: > > [ ID] Interval Transfer Bitrate > [ 5] 0.00-10.00 sec 117 MBytes 97.9 Mbits/sec > > However, throughput can return to expected levels after its driver requests > the high frequency mode. Requesting high frequency in the dwmac driver is > essential to maintain full throughput when the i.MX SoC adjusts bus speeds > for power savings. Oh, another one in one day :S Although this one feels much more like a bug that escaped testing because testing didn't use power saving? In any case, do you happen to have a user report you can mention here? Quoting stable rules: | Serious issues as reported by a user of a distribution kernel may also | be considered if they fix a notable performance or interactivity | issue. As these fixes are not as obvious and have a higher risk of a | subtle regression they should only be submitted by a distribution | kernel maintainer and include an addendum linking to a bugzilla entry | if it exists and additional information on the user-visible impact. And a Fixes tag would be good, please add. -- pw-bot: cr