Re: [PATCH v2 2/2] watchdog: pic32-dmt: Add PIC32 deadman timer driver

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

On 02/25/2016 10:30 AM, Joshua Henderson wrote:
> From: Purna Chandra Mandal <purna.mandal@microchip.com>
>
> Adds support for the deadman timer peripheral found on PIC32 class devices.
>
> The primary function of the deadman timer (DMT) is to reset the processor
> in the event of a software malfunction. The DMT is a free-running
> instruction fetch timer, which is clocked whenever an instruction fetch
> occurs until a count match occurs. Instructions are not fetched when
> the processor is in sleep mode.
>
> Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
> Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> ---
> Note: Please merge this patch series through the MIPS tree.
>
> Changes since v1:
> 	- Drop default y in Kconfig
> 	- Alphabetical include files
> 	- Use BIT() where appropriate
> 	- Replace cpu_relax() with nop() and comment why it's needed
> 	- Return bool on functions where appropriate
> 	- Add a way to break out of a tight loop
> 	- Remove static unused function
> 	- Remove redundant spinlock already covered by watchdog core
> 	- Remove unecessary error handling when enabling DMT
> 	- Drop implementation of .get_timeleft
> 	- Drop calculation of max_timeout
> 	- Cleanup dev_err() message contents
> 	- Fix race condition with watchdog device register
> 	- Unregister watchdog before disabling clock
> 	- Fix typo in driver name
> ---
>   drivers/watchdog/Kconfig     |   13 +++
>   drivers/watchdog/Makefile    |    1 +
>   drivers/watchdog/pic32-dmt.c |  260 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 274 insertions(+)
>   create mode 100644 drivers/watchdog/pic32-dmt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 543fa81..53747e9 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1427,6 +1427,19 @@ config PIC32_WDT
>   	  To compile this driver as a loadable module, choose M here.
>   	  The module will be called pic32-wdt.
>
> +config PIC32_DMT
> +	tristate "Microchip PIC32 Deadman Timer"
> +	select WATCHDOG_CORE
> +	depends on MACH_PIC32
> +	help
> +	  Watchdog driver for PIC32 instruction fetch counting timer. This specific
> +	  timer is typically be used in misson critical and safety critical
> +	  applications, where any single failure of the software functionality
> +	  and sequencing must be detected.
> +
> +	  To compile this driver as a loadable module, choose M here.
> +	  The module will be called pic32-dmt.
> +
>   # PARISC Architecture
>
>   # POWERPC Architecture
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 244ed80..d051c9c 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -154,6 +154,7 @@ obj-$(CONFIG_RALINK_WDT) += rt2880_wdt.o
>   obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
>   obj-$(CONFIG_MT7621_WDT) += mt7621_wdt.o
>   obj-$(CONFIG_PIC32_WDT) += pic32-wdt.o
> +obj-$(CONFIG_PIC32_DMT) += pic32-dmt.o
>
>   # PARISC Architecture
>
> diff --git a/drivers/watchdog/pic32-dmt.c b/drivers/watchdog/pic32-dmt.c
> new file mode 100644
> index 0000000..91801fa
> --- /dev/null
> +++ b/drivers/watchdog/pic32-dmt.c
> @@ -0,0 +1,260 @@
> +/*
> + * PIC32 deadman timer driver
> + *
> + * Purna Chandra Mandal <purna.mandal@microchip.com>
> + * Copyright (c) 2016, Microchip Technology Inc.
> + *
> + * 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.
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +

No pr_ function left, so this define can be removed.

> +#include <linux/clk.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm.h>
> +#include <linux/watchdog.h>
> +
> +#include <asm/mach-pic32/pic32.h>
> +
> +/* Deadman Timer Regs */
> +#define DMTCON_REG	0x00
> +#define DMTPRECLR_REG	0x10
> +#define DMTCLR_REG	0x20
> +#define DMTSTAT_REG	0x30
> +#define DMTCNT_REG	0x40
> +#define DMTPSCNT_REG	0x60
> +#define DMTPSINTV_REG	0x70
> +
> +/* Deadman Timer Regs fields */
> +#define DMT_ON			BIT(15)
> +#define DMT_STEP1_KEY		BIT(6)
> +#define DMT_STEP2_KEY		BIT(3)
> +#define DMTSTAT_WINOPN		BIT(0)
> +#define DMTSTAT_EVENT		BIT(5)
> +#define DMTSTAT_BAD2		BIT(6)
> +#define DMTSTAT_BAD1		BIT(7)
> +
> +/* Reset Control Register fields for watchdog */
> +#define RESETCON_DMT_TIMEOUT    BIT(5)
> +
> +struct pic32_dmt {
> +	void __iomem	*regs;
> +	struct clk	*clk;
> +};
> +
> +static inline void dmt_enable(struct pic32_dmt *dmt)
> +{
> +	writel(DMT_ON, PIC32_SET(dmt->regs + DMTCON_REG));
> +}
> +
> +static inline void dmt_disable(struct pic32_dmt *dmt)
> +{
> +	writel(DMT_ON, PIC32_CLR(dmt->regs + DMTCON_REG));
> +	/*
> +	 * Cannot touch registers in the CPU cycle following clearing the
> +	 * ON bit.
> +	 */
> +	nop();
> +}
> +
> +static inline int dmt_bad_status(struct pic32_dmt *dmt)
> +{
> +	u32 val;
> +
> +	val = readl(dmt->regs + DMTSTAT_REG);
> +	val &= (DMTSTAT_BAD1 | DMTSTAT_BAD2 | DMTSTAT_EVENT);
> +	if (val)
> +		return -EAGAIN;
> +
> +	return 0;
> +}
> +
> +static inline int dmt_keepalive(struct pic32_dmt *dmt)
> +{
> +	u32 v;
> +	u32 timeout = 500;
> +
> +	/* set pre-clear key */
> +	writel(DMT_STEP1_KEY << 8, dmt->regs + DMTPRECLR_REG);
> +
> +	/* wait for DMT window to open */
> +	while (--timeout) {
> +		v = readl(dmt->regs + DMTSTAT_REG) & DMTSTAT_WINOPN;
> +		if (v == DMTSTAT_WINOPN)
> +			break;
> +	}
> +
> +	/* apply key2 */
> +	writel(DMT_STEP2_KEY, dmt->regs + DMTCLR_REG);
> +
> +	/* check whether keys are latched correctly */
> +	return dmt_bad_status(dmt);
> +}
> +
> +static inline u32 pic32_dmt_get_timeout_secs(struct pic32_dmt *dmt)
> +{
> +	unsigned long rate;
> +
> +	rate = clk_get_rate(dmt->clk);
> +	if (rate)
> +		return readl(dmt->regs + DMTPSCNT_REG) / rate;
> +
> +	return -EINVAL;

Return value is unsigned, and the caller checks for 0 to identify an error,
so you need to return 0 here.

With that fixed, and the pr_fmt dropped, feel free to add

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

to the next revision of this patch.

Thanks,
Guenter