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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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