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Subject[PATCH v6 1/2] Use "request_muxed_region" in it87 watchdog drivers
Date
01 - Changes to it87 watchdog driver to use "request_muxed_region"
Serialize access to the hardware by using "request_muxed_region" macro defined
by Alan Cox. Call to this macro will hold off the requestor if the resource is
currently busy. The first call to request_muxed_region will attempt 10 times
to reserve the region before it gives up. This will typically get called from
the driver init routines. If this succeeds then subsequent calls wait forever
for the resource to be available.

The use of the above macro makes it possible to get rid of
spinlocks in it8712f_wdt.c and it87_wdt.c watchdog drivers.
This also greatly simplifies the implementation of it87_wdt.c driver.

Signed-off-by: Nat Gurumoorthy <natg@google.com>
---
diff --git a/drivers/watchdog/it8712f_wdt.c b/drivers/watchdog/it8712f_wdt.c
index 6143f52..8bf2524 100644
--- a/drivers/watchdog/it8712f_wdt.c
+++ b/drivers/watchdog/it8712f_wdt.c
@@ -51,7 +51,6 @@ MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");

static unsigned long wdt_open;
static unsigned expect_close;
-static spinlock_t io_lock;
static unsigned char revision;

/* Dog Food address - We use the game port address */
@@ -121,9 +120,46 @@ static inline void superio_select(int ldn)
outb(ldn, VAL);
}

-static inline void superio_enter(void)
+static inline int
+try_superio_enter(void)
{
- spin_lock(&io_lock);
+ int num_tries = 10;
+ /*
+ * Try to reserve REG and REG + 1 for exclusive access.
+ * Give up after 10 attempts.
+ */
+ while (num_tries--) {
+ if (!request_muxed_region(REG, 2, NAME)) {
+ if (num_tries)
+ continue;
+
+ /*
+ * Someone is holding the region. Give up.
+ */
+ pr_err("I/O address 0x%04x already in use\n", REG);
+ return -EBUSY;
+ }
+
+ break;
+ }
+
+ outb(0x87, REG);
+ outb(0x01, REG);
+ outb(0x55, REG);
+ outb(0x55, REG);
+ return 0;
+}
+
+static inline void
+superio_enter(void)
+{
+ /*
+ * Reserve REG and REG + 1 for exclusive access.
+ * Wait forever if you have to to gain access.
+ */
+ while (!request_muxed_region(REG, 2, NAME))
+ continue;
+
outb(0x87, REG);
outb(0x01, REG);
outb(0x55, REG);
@@ -134,7 +170,7 @@ static inline void superio_exit(void)
{
outb(0x02, REG);
outb(0x02, VAL);
- spin_unlock(&io_lock);
+ release_region(REG, 2);
}

static inline void it8712f_wdt_ping(void)
@@ -341,7 +377,9 @@ static int __init it8712f_wdt_find(unsigned short *address)
int err = -ENODEV;
int chip_type;

- superio_enter();
+ if (try_superio_enter())
+ return -EBUSY;
+
chip_type = superio_inw(DEVID);
if (chip_type != IT8712F_DEVID)
goto exit;
@@ -382,8 +420,6 @@ static int __init it8712f_wdt_init(void)
{
int err = 0;

- spin_lock_init(&io_lock);
-
if (it8712f_wdt_find(&address))
return -ENODEV;

diff --git a/drivers/watchdog/it87_wdt.c b/drivers/watchdog/it87_wdt.c
index b1bc72f..f1a0f03 100644
--- a/drivers/watchdog/it87_wdt.c
+++ b/drivers/watchdog/it87_wdt.c
@@ -137,7 +137,6 @@

static unsigned int base, gpact, ciract, max_units, chip_type;
static unsigned long wdt_status;
-static DEFINE_SPINLOCK(spinlock);

static int nogameport = DEFAULT_NOGAMEPORT;
static int exclusive = DEFAULT_EXCLUSIVE;
@@ -163,8 +162,46 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started, default="

/* Superio Chip */

-static inline void superio_enter(void)
+static inline int
+try_superio_enter(void)
{
+ int num_tries = 10;
+ /*
+ * Try to reserve REG and REG + 1 for exclusive access.
+ * Give up after 10 attempts.
+ */
+ while (num_tries--) {
+ if (!request_muxed_region(REG, 2, WATCHDOG_NAME)) {
+ if (num_tries)
+ continue;
+
+ /*
+ * Someone is holding the region. Give up.
+ */
+ pr_err("I/O address 0x%04x already in use\n", REG);
+ return -EBUSY;
+ }
+
+ break;
+ }
+
+ outb(0x87, REG);
+ outb(0x01, REG);
+ outb(0x55, REG);
+ outb(0x55, REG);
+ return 0;
+}
+
+static inline void
+superio_enter(void)
+{
+ /*
+ * Reserve REG and REG + 1 for exclusive access.
+ * Wait forever if you have to to gain access.
+ */
+ while (!request_muxed_region(REG, 2, WATCHDOG_NAME))
+ continue;
+
outb(0x87, REG);
outb(0x01, REG);
outb(0x55, REG);
@@ -175,6 +212,7 @@ static inline void superio_exit(void)
{
outb(0x02, REG);
outb(0x02, VAL);
+ release_region(REG, 2);
}

static inline void superio_select(int ldn)
@@ -257,9 +295,6 @@ static void wdt_keepalive(void)

static void wdt_start(void)
{
- unsigned long flags;
-
- spin_lock_irqsave(&spinlock, flags);
superio_enter();

superio_select(GPIO);
@@ -270,14 +305,10 @@ static void wdt_start(void)
wdt_update_timeout();

superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}

static void wdt_stop(void)
{
- unsigned long flags;
-
- spin_lock_irqsave(&spinlock, flags);
superio_enter();

superio_select(GPIO);
@@ -288,7 +319,6 @@ static void wdt_stop(void)
superio_outb(0x00, WDTVALMSB);

superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}

/**
@@ -303,8 +333,6 @@ static void wdt_stop(void)

static int wdt_set_timeout(int t)
{
- unsigned long flags;
-
if (t < 1 || t > max_units * 60)
return -EINVAL;

@@ -313,14 +341,12 @@ static int wdt_set_timeout(int t)
else
timeout = t;

- spin_lock_irqsave(&spinlock, flags);
if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
superio_enter();
superio_select(GPIO);
wdt_update_timeout();
superio_exit();
}
- spin_unlock_irqrestore(&spinlock, flags);
return 0;
}

@@ -339,11 +365,8 @@ static int wdt_set_timeout(int t)

static int wdt_get_status(int *status)
{
- unsigned long flags;
-
*status = 0;
if (testmode) {
- spin_lock_irqsave(&spinlock, flags);
superio_enter();
superio_select(GPIO);
if (superio_inb(WDTCTRL) & WDT_ZERO) {
@@ -353,7 +376,6 @@ static int wdt_get_status(int *status)
}

superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}
if (test_and_clear_bit(WDTS_KEEPALIVE, &wdt_status))
*status |= WDIOF_KEEPALIVEPING;
@@ -560,16 +582,15 @@ static int __init it87_wdt_init(void)
int rc = 0;
int try_gameport = !nogameport;
u8 chip_rev;
- unsigned long flags;

wdt_status = 0;

- spin_lock_irqsave(&spinlock, flags);
- superio_enter();
+ if (try_superio_enter())
+ return -EBUSY;
+
chip_type = superio_inw(CHIPID);
chip_rev = superio_inb(CHIPREV) & 0x0f;
superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);

switch (chip_type) {
case IT8702_ID:
@@ -603,7 +624,6 @@ static int __init it87_wdt_init(void)
return -ENODEV;
}

- spin_lock_irqsave(&spinlock, flags);
superio_enter();

superio_select(GPIO);
@@ -621,14 +641,12 @@ static int __init it87_wdt_init(void)
gpact = superio_inb(ACTREG);
superio_outb(0x01, ACTREG);
superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
if (request_region(base, 1, WATCHDOG_NAME))
set_bit(WDTS_USE_GP, &wdt_status);
else
rc = -EIO;
} else {
superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}

/* If we haven't Gameport support, try to get CIR support */
@@ -646,7 +664,6 @@ static int __init it87_wdt_init(void)
goto err_out;
}
base = CIR_BASE;
- spin_lock_irqsave(&spinlock, flags);
superio_enter();

superio_select(CIR);
@@ -660,7 +677,6 @@ static int __init it87_wdt_init(void)
}

superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}

if (timeout < 1 || timeout > max_units * 60) {
@@ -711,21 +727,17 @@ err_out_reboot:
err_out_region:
release_region(base, test_bit(WDTS_USE_GP, &wdt_status) ? 1 : 8);
if (!test_bit(WDTS_USE_GP, &wdt_status)) {
- spin_lock_irqsave(&spinlock, flags);
superio_enter();
superio_select(CIR);
superio_outb(ciract, ACTREG);
superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}
err_out:
if (try_gameport) {
- spin_lock_irqsave(&spinlock, flags);
superio_enter();
superio_select(GAMEPORT);
superio_outb(gpact, ACTREG);
superio_exit();
- spin_unlock_irqrestore(&spinlock, flags);
}

return rc;
@@ -733,10 +745,6 @@ err_out:

static void __exit it87_wdt_exit(void)
{
- unsigned long flags;
- int nolock;
-
- nolock = !spin_trylock_irqsave(&spinlock, flags);
superio_enter();
superio_select(GPIO);
superio_outb(0x00, WDTCTRL);
@@ -752,8 +760,6 @@ static void __exit it87_wdt_exit(void)
superio_outb(ciract, ACTREG);
}
superio_exit();
- if (!nolock)
- spin_unlock_irqrestore(&spinlock, flags);

misc_deregister(&wdt_miscdev);
unregister_reboot_notifier(&wdt_notifier);
--
1.7.3.1


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