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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 D899FC3A59E for ; Mon, 26 Aug 2019 08:57:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B15EC206BA for ; Mon, 26 Aug 2019 08:57:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730377AbfHZI5R (ORCPT ); Mon, 26 Aug 2019 04:57:17 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:35661 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727974AbfHZI5R (ORCPT ); Mon, 26 Aug 2019 04:57:17 -0400 Received: from lupine.hi.pengutronix.de ([2001:67c:670:100:3ad5:47ff:feaf:1a17] helo=lupine) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1i2AoN-0003gN-GM; Mon, 26 Aug 2019 10:57:15 +0200 Message-ID: <1566809829.3842.4.camel@pengutronix.de> Subject: Re: [RESEND PATCHv4 1/1] drivers/amba: add reset control to amba bus probe From: Philipp Zabel To: Dinh Nguyen , Linus Walleij Cc: "linux-kernel@vger.kernel.org" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Rob Herring , Russell King , Frank Rowand , Kees Cook , Anton Vorontsov , Colin Cross , Tony Luck , Daniel Thompson , Manivannan Sadhasivam , Linux ARM Date: Mon, 26 Aug 2019 10:57:09 +0200 In-Reply-To: References: <20190820145834.7301-1-dinguyen@kernel.org> <20190820145834.7301-2-dinguyen@kernel.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:100:3ad5:47ff:feaf:1a17 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dinh, Linus, On Fri, 2019-08-23 at 10:42 -0500, Dinh Nguyen wrote: > > On 8/23/19 4:19 AM, Linus Walleij wrote: > > On Tue, Aug 20, 2019 at 4:58 PM Dinh Nguyen wrote: > > > > > @@ -401,6 +402,26 @@ static int amba_device_try_add(struct amba_device *dev, struct resource *parent) > > > ret = amba_get_enable_pclk(dev); > > > if (ret == 0) { > > > u32 pid, cid; > > > + int count; > > > + struct reset_control *rstc; > > > + > > > + /* > > > + * Find reset control(s) of the amba bus and de-assert them. > > > + */ > > > + count = reset_control_get_count(&dev->dev); The reset_control_get_count() inline stub returns -ENOENT, so the compiler can throw away the complete loop. > > > + while (count > 0) { > > > + rstc = of_reset_control_get_shared_by_index(dev->dev.of_node, count - 1); Since resets are looked up with of_reset_control_get, I'd use of_reset_control_get_count() above for consistency. But see below: > > > + if (IS_ERR(rstc)) { > > > + if (PTR_ERR(rstc) == -EPROBE_DEFER) > > > + ret = -EPROBE_DEFER; > > > + else > > > + dev_err(&dev->dev, "Can't get amba reset!\n"); > > > + break; > > > + } > > > + reset_control_deassert(rstc); > > > + reset_control_put(rstc); > > > + count--; > > > + } It looks like the order of deassertions is irrelevant. If so, You can use of_reset_control_array_get() to simplify this: + rstc = of_reset_control_array_get_optional_shared(dev->dev.of_node); + if (IS_ERR(rstc)) { + if (PTR_ERR(rstc) != -EPROBE_DEFER) + dev_err(&dev->dev, "Can't get amba reset!\n"); + return PTR_ERR(rstc); + } + reset_control_deassert(rstc); + reset_control_put(rstc); > > I'm not normally a footprint person, but the looks of the stubs in > > makes me suspicious whether this will have zero impact > > in size on platforms without reset controllers. > > > > Can you just ls -al on the kernel without CONFIG_RESET_CONTROLLER > > before and after this patch and ascertain that it has zero footprint effect? > > Thanks for the review. I checked it, and indeed, it does have a zero > footprint effect. > > > > > If it doesn't I'd sure like to break this into its own function and > > stick a if (!IS_ENABLED(CONFIG_RESET_CONTROLLER)) return 0; > > in there to make sure the compiler drops it. > > > > Also it'd be nice to get Philipp's ACK on the semantics, though they > > look correct to me. regards Philipp