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Subject[PATCH 11/11, corrected] mv64x60_wdt: Rework the timeout register manipulation
mv64x60_wdt: Rework the timeout register manipulation

Consolidate the timeout config register modification into a single
function. Also, use the enabled flag in the config register to
determine whether the timer is enabled instead of a separately
maintained flag, MV64x60_WDOG_FLAG_ENABLED.

Add spinlock protection around enabling/disabling the watchdog timer.

Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
---
Oops! I mistakenly sent an earlier version of this patch. Please
disregard it and replace it with this one.
drivers/char/watchdog/mv64x60_wdt.c | 90 +++++++++++++++-----------
1 file changed, 54 insertions(+), 36 deletions(-)
Index: linux-2.6-powerpc-wdt/drivers/char/watchdog/mv64x60_wdt.c
===================================================================
--- linux-2.6-powerpc-wdt.orig/drivers/char/watchdog/mv64x60_wdt.c 2007-07-20 20:05:04.000000000 +0000
+++ linux-2.6-powerpc-wdt/drivers/char/watchdog/mv64x60_wdt.c 2007-07-24 18:28:58.000000000 +0000
@@ -29,75 +29,95 @@

#define MV64x60_WDT_WDC_OFFSET 0

-/* MV64x60 WDC (config) register access definitions */
-#define MV64x60_WDC_CTL1_MASK (3 << 24)
-#define MV64x60_WDC_CTL1(val) ((val & 3) << 24)
-#define MV64x60_WDC_CTL2_MASK (3 << 26)
-#define MV64x60_WDC_CTL2(val) ((val & 3) << 26)
+/*
+ * The watchdog configuration register contains a pair of 2-bit fields,
+ * 1. a reload field, bits 27-26, which triggers a reload of
+ * the countdown register, and
+ * 2. an enable field, bits 25-24, which toggles between
+ * enabling and disabling the watchdog timer.
+ * Bit 31 is a read-only field which indicates whether the
+ * watchdog timer is currently enabled.
+ *
+ * The low 24 bits contain the timer reload value.
+ */
+#define MV64x60_WDC_ENABLE_SHIFT 24
+#define MV64x60_WDC_SERVICE_SHIFT 26
+#define MV64x60_WDC_ENABLED_SHIFT 31
+
+#define MV64x60_WDC_ENABLED_TRUE 1
+#define MV64x60_WDC_ENABLED_FALSE 0

/* Flags bits */
#define MV64x60_WDOG_FLAG_OPENED 0
-#define MV64x60_WDOG_FLAG_ENABLED 1

static unsigned long wdt_flags;
static int wdt_status;
static void __iomem *mv64x60_wdt_regs;
static int mv64x60_wdt_timeout;
+static int mv64x60_wdt_count;
static unsigned int bus_clk;
static char expect_close;
+static DEFINE_SPINLOCK(mv64x60_wdt_spinlock);

static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

-static void mv64x60_wdt_reg_write(u32 val)
+static int mv64x60_wdt_toggle_wdc(int enabled_predicate, int field_shift)
{
- /* Allow write only to CTL1 / CTL2 fields, retaining values in
- * other fields.
- */
- u32 data = readl(mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
- data &= ~(MV64x60_WDC_CTL1_MASK | MV64x60_WDC_CTL2_MASK);
- data |= val;
- writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
+ u32 data;
+ u32 enabled;
+ int ret = 0;
+
+ spin_lock(&mv64x60_wdt_spinlock);
+ data = readl(mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
+ enabled = (data >> MV64x60_WDC_ENABLED_SHIFT) & 1;
+
+ /* only toggle the requested field if enabled state matches predicate */
+ if ((enabled ^ enabled_predicate) == 0) {
+ /* We write a 1, then a 2 -- to the appropriate field */
+ data = (1 << field_shift) | mv64x60_wdt_count;
+ writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
+
+ data = (2 << field_shift) | mv64x60_wdt_count;
+ writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
+ ret = 1;
+ }
+ spin_unlock(&mv64x60_wdt_spinlock);
+
+ return ret;
}

static void mv64x60_wdt_service(void)
{
- /* Write 01 followed by 10 to CTL2 */
- mv64x60_wdt_reg_write(MV64x60_WDC_CTL2(0x01));
- mv64x60_wdt_reg_write(MV64x60_WDC_CTL2(0x02));
+ mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_TRUE,
+ MV64x60_WDC_SERVICE_SHIFT);
}

-static void mv64x60_wdt_handler_disable(void)
+static void mv64x60_wdt_handler_enable(void)
{
- if (test_and_clear_bit(MV64x60_WDOG_FLAG_ENABLED, &wdt_flags)) {
- /* Write 01 followed by 10 to CTL1 */
- mv64x60_wdt_reg_write(MV64x60_WDC_CTL1(0x01));
- mv64x60_wdt_reg_write(MV64x60_WDC_CTL1(0x02));
- printk(KERN_NOTICE "mv64x60_wdt: watchdog deactivated\n");
+ if (mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_FALSE,
+ MV64x60_WDC_ENABLE_SHIFT)) {
+ mv64x60_wdt_service();
+ printk(KERN_NOTICE "mv64x60_wdt: watchdog activated\n");
}
}

-static void mv64x60_wdt_handler_enable(void)
+static void mv64x60_wdt_handler_disable(void)
{
- if (!test_and_set_bit(MV64x60_WDOG_FLAG_ENABLED, &wdt_flags)) {
- /* Write 01 followed by 10 to CTL1 */
- mv64x60_wdt_reg_write(MV64x60_WDC_CTL1(0x01));
- mv64x60_wdt_reg_write(MV64x60_WDC_CTL1(0x02));
- printk(KERN_NOTICE "mv64x60_wdt: watchdog activated\n");
- }
+ if (mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_TRUE,
+ MV64x60_WDC_ENABLE_SHIFT))
+ printk(KERN_NOTICE "mv64x60_wdt: watchdog deactivated\n");
}

-static void mv64x60_wdt_set_timeout(int timeout)
+static void mv64x60_wdt_set_timeout(unsigned int timeout)
{
/* maximum bus cycle count is 0xFFFFFFFF */
if (timeout > 0xFFFFFFFF / bus_clk)
timeout = 0xFFFFFFFF / bus_clk;

+ mv64x60_wdt_count = timeout * bus_clk >> 8;
mv64x60_wdt_timeout = timeout;
- writel((timeout * bus_clk) >> 8,
- mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
- mv64x60_wdt_service();
}

static int mv64x60_wdt_open(struct inode *inode, struct file *file)
@@ -108,7 +128,6 @@ static int mv64x60_wdt_open(struct inode
if (nowayout)
__module_get(THIS_MODULE);

- mv64x60_wdt_service();
mv64x60_wdt_handler_enable();

return nonseekable_open(inode, file);
@@ -270,7 +289,6 @@ static int __devexit mv64x60_wdt_remove(
{
misc_deregister(&mv64x60_wdt_miscdev);

- mv64x60_wdt_service();
mv64x60_wdt_handler_disable();

iounmap(mv64x60_wdt_regs);
-
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