On 02/26/2016 07:11 AM, Guenter Roeck wrote:

On 02/25/2016 10:30 AM, Joshua Henderson wrote:

quoted

From: Purna Chandra Mandal <redacted>

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 <redacted>
Signed-off-by: Joshua Henderson <redacted>
Cc: Ralf Baechle <ralf-6z/3iImG2C8G8FEW9MqTrA@public.gmane.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-UWL1GkI3JZL3oGB3hsPCZA@public.gmane.org>
+ * 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.

Ack.

quoted

+#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 <redacted>

to the next revision of this patch.

Ack.

Thanks,
Josh
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