Re: [PATCH v2 2/2] watchdog: pic32-dmt: Add PIC32 deadman timer driver
From: Guenter Roeck
Date: Fri Feb 26 2016 - 09:12:09 EST
On 02/25/2016 10:30 AM, Joshua Henderson wrote:
From: Purna Chandra Mandal <purna.mandal@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Joshua Henderson <joshua.henderson@xxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxx>
+ * 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@xxxxxxxxxxxx>
to the next revision of this patch.
Thanks,
Guenter