Re: [RFC 1/4] watchdog: ni9x3x_wdt: Add NI 903x/913x watchdog driver

[Guenter Roeck <linux@roeck-us.net>]

On 02/04/2016 05:28 PM, Kyle Roeschley wrote:
> Add support for the watchdog timer on NI cRIO-903x and cDAQ-913x real-
> time controllers.
>
> Signed-off-by: Jeff Westfahl <jeff.westfahl@ni.com>
> Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
> ---
>   drivers/watchdog/Kconfig      |  11 ++
>   drivers/watchdog/Makefile     |   1 +
>   drivers/watchdog/ni9x3x_wdt.c | 264 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 276 insertions(+)
>   create mode 100644 drivers/watchdog/ni9x3x_wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 0f6d851..18bd13a 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1214,6 +1214,17 @@ config SBC_EPX_C3_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called sbc_epx_c3.
>
> +config NI9X3X_WDT
> +	tristate "NI 903x/913x Watchdog"
> +	depends on X86 && ACPI
> +	select WATCHDOG_CORE
> +	---help---
> +	  This is the driver for the watchdog timer on the National Instruments
> +	  903x/913x real-time controllers.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ni9x3x_wdt.
> +
>   # M32R Architecture
>
>   # M68K Architecture
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index f566753..527978b 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -126,6 +126,7 @@ obj-$(CONFIG_MACHZ_WDT) += machzwd.o
>   obj-$(CONFIG_SBC_EPX_C3_WATCHDOG) += sbc_epx_c3.o
>   obj-$(CONFIG_INTEL_SCU_WATCHDOG) += intel_scu_watchdog.o
>   obj-$(CONFIG_INTEL_MID_WATCHDOG) += intel-mid_wdt.o
> +obj-$(CONFIG_NI9X3X_WDT) += ni9x3x_wdt.o
>
>   # M32R Architecture
>
> diff --git a/drivers/watchdog/ni9x3x_wdt.c b/drivers/watchdog/ni9x3x_wdt.c
> new file mode 100644
> index 0000000..2cb5627
> --- /dev/null
> +++ b/drivers/watchdog/ni9x3x_wdt.c
> @@ -0,0 +1,264 @@
> +/*
> + * Copyright (C) 2013 National Instruments Corp.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/watchdog.h>
> +
> +#define NIWD_CONTROL	0x01
> +#define NIWD_COUNTER2	0x02
> +#define NIWD_COUNTER1	0x03
> +#define NIWD_COUNTER0	0x04
> +#define NIWD_SEED2	0x05
> +#define NIWD_SEED1	0x06
> +#define NIWD_SEED0	0x07
> +
> +#define NIWD_IO_SIZE	0x08
> +
> +#define NIWD_CONTROL_MODE		0x80
> +#define NIWD_CONTROL_PROC_RESET		0x20
> +#define NIWD_CONTROL_PET		0x10
> +#define NIWD_CONTROL_RUNNING		0x08
> +#define NIWD_CONTROL_CAPTURECOUNTER	0x04
> +#define NIWD_CONTROL_RESET		0x02
> +#define NIWD_CONTROL_ALARM		0x01
> +
> +#define NIWD_PERIOD_NS		30720
> +#define NIWD_MIN_TIMEOUT	1
> +#define NIWD_MAX_TIMEOUT	515
> +#define NIWD_DEFAULT_TIMEOUT	60
> +
> +#define NI9X3X_WDT_NAME		"ni9x3x_wdt"
> +
> +#define to_ni9x3x_wdt(_wdog)	container_of(_wdog, struct ni9x3x_wdt, wdog)
> +
> +struct ni9x3x_wdt {
> +	struct acpi_device *acpi_device;
> +	u16 io_base;
> +	u16 io_size;
> +	spinlock_t lock;
> +	struct watchdog_device wdog;
> +};
> +
> +static void ni9x3x_wdt_start(struct ni9x3x_wdt *wdt)
> +{
> +	u8 control = inb(wdt->io_base + NIWD_CONTROL);
> +
> +	outb(control | NIWD_CONTROL_RESET, wdt->io_base + NIWD_CONTROL);
> +	outb(control | NIWD_CONTROL_PET, wdt->io_base + NIWD_CONTROL);
> +}
> +
> +static int ni9x3x_wdt_wdd_set_timeout(struct watchdog_device *wdd,
> +				      unsigned int timeout)
> +{
> +	struct ni9x3x_wdt *wdt = to_ni9x3x_wdt(wdd);
> +	u32 counter = timeout * (1000000000 / NIWD_PERIOD_NS);
> +
> +	outb(((0x00FF0000 & counter) >> 16), wdt->io_base + NIWD_SEED2);
> +	outb(((0x0000FF00 & counter) >> 8), wdt->io_base + NIWD_SEED1);
> +	outb((0x000000FF & counter), wdt->io_base + NIWD_SEED0);
> +
> +	return 0;
> +}
> +
> +static unsigned int ni9x3x_wdt_wdd_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct ni9x3x_wdt *wdt = to_ni9x3x_wdt(wdd);
> +	u8 control, counter0, counter1, counter2;
> +	u32 counter;
> +
> +	control = inb(wdt->io_base + NIWD_CONTROL);
> +	control |= NIWD_CONTROL_CAPTURECOUNTER;
> +	outb(control, wdt->io_base + NIWD_CONTROL);
> +
> +	counter2 = inb(wdt->io_base + NIWD_COUNTER2);
> +	counter1 = inb(wdt->io_base + NIWD_COUNTER1);
> +	counter0 = inb(wdt->io_base + NIWD_COUNTER0);
> +
> +	counter = (counter2 << 16) | (counter1 << 8) | counter0;
> +	counter = (counter * (u64)NIWD_PERIOD_NS) / 1000000000;
> +

The maximum value of 'counter' from the registers is
	515 * (1000000000/30720) = 16764280

Multiplying this value by 30720 yields 514998681600, much more than
fits in a 32 bit value. This means you'll have to use u64 for the
counter variable and use 64 bit operations for the divide operation.

Guenter