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 X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90543C3A5A1 for ; Wed, 28 Aug 2019 13:34:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64D20233A1 for ; Wed, 28 Aug 2019 13:34:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566999266; bh=Wr54NI83bMpyXaEztjls1DUnCnQYPgiyLdE1sjyNxlQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=zUo7y7TsvUuvYvkNoDLV4l0/TH+Uib2yp5O2qgyJtz9SP43oFSwyRWrQ+BUyGsneh XYUdlsjGuIgW387kSvLfLzNQAAyuIltwNR5Y9OyDjbdLtYSg9/WNwJ+0Tu8kTFGSy4 ftYbCDcBKntczdr3VHmkheq+WuE5ViERDHrXLh2U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726693AbfH1NeZ (ORCPT ); Wed, 28 Aug 2019 09:34:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:44164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726394AbfH1NeY (ORCPT ); Wed, 28 Aug 2019 09:34:24 -0400 Received: from [192.168.1.17] (cpe-70-114-128-244.austin.res.rr.com [70.114.128.244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C73412339E; Wed, 28 Aug 2019 13:34:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566999262; bh=Wr54NI83bMpyXaEztjls1DUnCnQYPgiyLdE1sjyNxlQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=jbiK7gaBFdskrYs8/YWVQA34MqdEEbs+AZKoLkLe4MJrC5JyYaAxq+6tjT2hImJnn lw+e1YqKsYHtW2d9eOfxZPo5nVsJyE2NnOMjDCEOsbykLoYkeJOZUtKZBdBGKHQOcF 1xib9MERTpIW23ahudscdrtFfJB5QaVLufv861Ig= Subject: Re: [PATCHv5] drivers/amba: add reset control to amba bus probe To: =?UTF-8?Q?Valdis_Kl=c4=93tnieks?= Cc: linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, robh@kernel.org, linux@armlinux.org.uk, frowand.list@gmail.com, keescook@chromium.org, anton@enomsg.org, ccross@android.com, tony.luck@intel.com, daniel.thompson@linaro.org, linus.walleij@linaro.org, manivannan.sadhasivam@linaro.org, linux-arm-kernel@lists.infradead.org, p.zabel@pengutronix.de References: <20190826154252.22952-1-dinguyen@kernel.org> <30608.1566933924@turing-police> From: Dinh Nguyen Openpgp: preference=signencrypt Autocrypt: addr=dinguyen@kernel.org; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <30608.1566933924@turing-police> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 8/27/19 2:25 PM, Valdis Kl?tnieks wrote: > On Mon, 26 Aug 2019 10:42:52 -0500, Dinh Nguyen said: >> The primecell controller on some SoCs, i.e. SoCFPGA, is held in >> reset by default. Until recently, the DMA controller was brought >> out of reset by the bootloader(i.e. U-Boot). But a recent change >> in U-Boot, the peripherals that are not used are held in reset >> and are left to Linux to bring them out of reset. >> >> Add a mechanism for getting the reset property and de-assert the >> primecell module from reset if found. This is a not a hard fail >> if the reset properti is not present in the device tree node, so >> the driver will continue to probe. > > Does this DTRT for both old and new U-Boots? My naive reading of > this patch What is a DTRT? > says on an old U-Boot, we end up attempting to bring it out of > reset even though they had already been brought out. > If the peripheral is already out of reset, de-asserting the reset has no affect. 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