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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i2Aof-0004PN-Qv; Mon, 26 Aug 2019 08:57:33 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i2Aod-0004Oj-9y for linux-arm-kernel@lists.infradead.org; Mon, 26 Aug 2019 08:57:32 +0000 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 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> X-Mailer: Evolution 3.22.6-1+deb9u2 Mime-Version: 1.0 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-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190826_015731_349698_5E5A39F4 X-CRM114-Status: GOOD ( 21.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Daniel Thompson , Tony Luck , Manivannan Sadhasivam , Kees Cook , Rob Herring , Anton Vorontsov , Russell King , "linux-kernel@vger.kernel.org" , Colin Cross , Frank Rowand , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel