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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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