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Date: Fri, 26 Feb 2016 06:11:58 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Joshua Henderson <joshua.henderson@...rochip.com>,
linux-kernel@...r.kernel.org
Cc: linux-mips@...ux-mips.org, ralf@...ux-mips.org,
Purna Chandra Mandal <purna.mandal@...rochip.com>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Wim Van Sebroeck <wim@...ana.be>, devicetree@...r.kernel.org,
linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v2 2/2] watchdog: pic32-dmt: Add PIC32 deadman timer
driver
On 02/25/2016 10:30 AM, Joshua Henderson wrote:
> From: Purna Chandra Mandal <purna.mandal@...rochip.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@...rochip.com>
> Signed-off-by: Joshua Henderson <joshua.henderson@...rochip.com>
> Cc: Ralf Baechle <ralf@...ux-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@...rochip.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@...ck-us.net>
to the next revision of this patch.
Thanks,
Guenter
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