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    SubjectRe: [PATCH 7/9 -v2] imx: serial: use rational library function
    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 <os@emlix.com>
    > ---
    > 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 <linux/serial_core.h>
    > #include <linux/serial.h>
    > #include <linux/clk.h>
    > +#include <linux/rational.h>
    >
    > #include <asm/io.h>
    > #include <asm/irq.h>
    > @@ -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?

    >
    > - /* 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;
    >
    > 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
    >
    >

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