Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932289Ab3CPAkz (ORCPT ); Fri, 15 Mar 2013 20:40:55 -0400 Received: from blu0-omc1-s29.blu0.hotmail.com ([65.55.116.40]:9925 "EHLO blu0-omc1-s29.blu0.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932125Ab3CPAkx convert rfc822-to-8bit (ORCPT ); Fri, 15 Mar 2013 20:40:53 -0400 X-EIP: [M3NTUEPvFFVv63H++PT5Rzp1RrcvDaVg4kzpK1EeELA=] X-Originating-Email: [emilio@elopez.com.ar] Message-ID: Date: Fri, 15 Mar 2013 21:40:47 -0300 From: =?ISO-8859-1?Q?Emilio_L=F3pez?= User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Russell King - ARM Linux CC: Maxime Ripard , linux-arm-kernel@lists.infradead.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, sunny@allwinnertech.com, shuge@allwinnertech.com, Jiri Slaby , kevin@allwinnertech.com Subject: Re: [PATCH 1/6] serial: 8250_dw: add support for clk api References: <1363377988-4966-1-git-send-email-maxime.ripard@free-electrons.com> <1363377988-4966-2-git-send-email-maxime.ripard@free-electrons.com> <20130315223917.GZ4977@n2100.arm.linux.org.uk> <20130316002952.GA4977@n2100.arm.linux.org.uk> In-Reply-To: <20130316002952.GA4977@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8BIT X-OriginalArrivalTime: 16 Mar 2013 00:40:52.0321 (UTC) FILETIME=[E96FFD10:01CE21DE] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2590 Lines: 77 El 15/03/13 21:29, Russell King - ARM Linux escribi?: > On Fri, Mar 15, 2013 at 09:15:11PM -0300, Emilio L?pez wrote: >> Hello Russell, >> >> El 15/03/13 19:39, Russell King - ARM Linux escribi?: >>> On Fri, Mar 15, 2013 at 09:06:23PM +0100, Maxime Ripard wrote: >>>> + /* clock got configured through clk api, all done */ >>>> + if (p->uartclk) >>> >>> if (IS_ERR(p->uartclk)) >>> >> >> Isn't IS_ERR for pointers? p->uartclk is an unsigned int > > Right, sorry, ignore that. > >>>> + return 0; >>>> + >>>> + /* try to find out clock frequency from DT as fallback */ >>>> if (of_property_read_u32(np, "clock-frequency", &val)) { >>>> - dev_err(p->dev, "no clock-frequency property set\n"); >>>> + dev_err(p->dev, "clk or clock-frequency not defined\n"); >>>> return -EINVAL; >>>> } >>>> p->uartclk = val; >>>> @@ -294,9 +301,21 @@ static int dw8250_probe(struct platform_device *pdev) >>>> if (!uart.port.membase) >>>> return -ENOMEM; >>>> >>>> + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL); >>>> + if (!data) >>>> + return -ENOMEM; >>>> + >>>> + data->clk = devm_clk_get(&pdev->dev, NULL); >>>> + if (IS_ERR(data->clk)) >>>> + data->clk = NULL; >>>> + else >>>> + clk_prepare_enable(data->clk); >>> >>> if (!IS_ERR(data->clk)) >>> clk_prepare_enable(data->clk); >>> >> >> See below >> >>>> + >>>> uart.port.iotype = UPIO_MEM; >>>> uart.port.serial_in = dw8250_serial_in; >>>> uart.port.serial_out = dw8250_serial_out; >>>> + uart.port.private_data = data; >>>> + uart.port.uartclk = clk_get_rate(data->clk); >>> >>> What if data->clk is invalid? >>> >>> if (!IS_ERR(data->clk) >>> uart.port.uartclk = clk_get_rate(data->clk); >>> >> >> I'm not sure if it is coincidental or the way it is supposed to be, but >> when using the common clock framework, if you pass a NULL to >> clk_get_rate, the function explicitly checks for it and returns 0. I >> relied on that behaviour when implementing this; see the if..else block >> above. Is this not always the case on other clock drivers? > > That's something that the common clock framework decided to do. It's > not a defined part of the API though, so drivers shouldn't rely on > this behaviour meaning anything special. Ok then, I'll rework the error checking on the clock calls and get a new patch sent. Thanks for the clarification. Emilio -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/