Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932311Ab3CPAbS (ORCPT ); Fri, 15 Mar 2013 20:31:18 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:36675 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932186Ab3CPAbR (ORCPT ); Fri, 15 Mar 2013 20:31:17 -0400 Date: Sat, 16 Mar 2013 00:29:52 +0000 From: Russell King - ARM Linux To: Emilio =?iso-8859-1?Q?L=F3pez?= 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 Message-ID: <20130316002952.GA4977@n2100.arm.linux.org.uk> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2394 Lines: 71 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. -- 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/