Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756570AbZFOHkp (ORCPT ); Mon, 15 Jun 2009 03:40:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752183AbZFOHki (ORCPT ); Mon, 15 Jun 2009 03:40:38 -0400 Received: from mx1.emlix.com ([193.175.82.87]:36817 "EHLO mx1.emlix.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751646AbZFOHkh (ORCPT ); Mon, 15 Jun 2009 03:40:37 -0400 From: "Oskar Schirmer" Date: Mon, 15 Jun 2009 09:40:33 +0200 To: Sascha Hauer Cc: Oskar Schirmer , Sascha Hauer , linux-kernel@vger.kernel.org, Andrew Morton , Alan Cox Subject: Re: [PATCH 7/9 -v2] imx: serial: use rational library function Message-ID: <20090615074032.GB3984@emlix.com> References: <1244635716-23315-1-git-send-email-os@emlix.com> <1244635716-23315-8-git-send-email-os@emlix.com> <20090612071649.GA31396@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20090612071649.GA31396@pengutronix.de> Organization: emlix GmbH User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4237 Lines: 126 On Fri, Jun 12, 2009 at 09:16:49 +0200, Sascha Hauer wrote: > Hi Oskar, > > On Wed, Jun 10, 2009 at 02:08:34PM +0200, Oskar Schirmer wrote: > > for calculation of numerator and denominator > > used in baud rate setting, use generic library function > > for optimum settings. > > > > Signed-off-by: Oskar Schirmer > > --- > > drivers/serial/Kconfig | 1 + > > drivers/serial/imx.c | 30 ++++++++++-------------------- > > 2 files changed, 11 insertions(+), 20 deletions(-) > > > > diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig > > index 343e3a3..0ecb4c4 100644 > > --- a/drivers/serial/Kconfig > > +++ b/drivers/serial/Kconfig > > @@ -833,6 +833,7 @@ config SERIAL_IMX > > bool "IMX serial port support" > > depends on ARM && (ARCH_IMX || ARCH_MXC) > > select SERIAL_CORE > > + select RATIONAL > > help > > If you have a machine based on a Motorola IMX CPU you > > can enable its onboard serial port by enabling this option. > > diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c > > index 60892a2..11f93e2 100644 > > --- a/drivers/serial/imx.c > > +++ b/drivers/serial/imx.c > > @@ -41,6 +41,7 @@ > > #include > > #include > > #include > > +#include > > > > #include > > #include > > @@ -670,7 +671,8 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios, > > unsigned long flags; > > unsigned int ucr2, old_ucr1, old_txrxen, baud, quot; > > unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8; > > - unsigned int div, num, denom, ufcr; > > + unsigned int div, ufcr; > > + unsigned long num, denom; > > > > /* > > * If we don't support modem control lines, don't allow > > @@ -772,32 +774,20 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios, > > if (!div) > > div = 1; > > > > - num = baud; > > - denom = port->uartclk / div / 16; > > + rational_best_approximation(16 * div * baud, sport->port.uartclk, > > + 1 << 16, 1 << 16, &num, &denom); > > Reading the example you have given for rational_best_approximation() in > the last patch this should be (1 << 16) - 1, right? No, the registers hold values minus one, e.g. to select numerator = 14, set UBIR = 13. Thus, the maximum value for rate calculation is 1 << 16, not 0xFFFF. For the "minus 1", see below. > > > > > - /* shift num and denom right until they fit into 16 bits */ > > - while (num > 0x10000 || denom > 0x10000) { > > - num >>= 1; > > - denom >>= 1; > > - } > > - if (num > 0) > > - num -= 1; > > - if (denom > 0) > > - denom -= 1; > > - > > - writel(num, sport->port.membase + UBIR); > > - writel(denom, sport->port.membase + UBMR); > > - > > - if (div == 7) > > - div = 6; /* 6 in RFDIV means divide by 7 */ > > - else > > - div = 6 - div; > > + num -= 1; > > + denom -= 1; This is where rate calculation values are decreased for register purpose. > > > > ufcr = readl(sport->port.membase + UFCR); > > ufcr = (ufcr & (~UFCR_RFDIV)) | > > (div << 7); > > writel(ufcr, sport->port.membase + UFCR); > > > > + writel(num, sport->port.membase + UBIR); > > + writel(denom, sport->port.membase + UBMR); > > + > > #ifdef ONEMS > > writel(sport->port.uartclk / div / 1000, sport->port.membase + ONEMS); > > #endif > > -- > > 1.5.3.7 > > > > > > -- > Pengutronix e.K. | | > Industrial Linux Solutions | http://www.pengutronix.de/ | > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | > -- oskar schirmer, emlix gmbh, http://www.emlix.com fon +49 551 30664-0, fax -11, bahnhofsallee 1b, 37081 göttingen, germany geschäftsführung: dr. uwe kracke, dr. cord seele, ust-idnr.: de 205 198 055 sitz der gesellschaft: göttingen, amtsgericht göttingen hr b 3160 emlix - your embedded linux partner -- 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/