Make all it87 drivers SMP safe

PATCH Superseded Nat Gurumoorthy 2 participants 5 messages Apr 11, 2011 – Apr 12, 2011

Subsystems (3)

Hardware monitoring Watchdog device drivers IT87 hardware monitoring driver

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Nat Gurumoorthy

author

2011-04-11 23:50 UTC #0 lore raw

v4 cover Make all it87 drivers SMP safe

There are 3 different drivers that touch the it87 hardware registers. The 3 drivers have been written independently and access the it87 hardware registers assuming they are the only driver accessing it. This change attempts to 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 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.

01 - Changes to it87 watchdog driver to use "request_muxed_region"
drivers/watchdog/it8712f_wdt.c drivers/watchdog/it87_wdt.c

02 - Chages to hwmon it87 driver to use "request_muxed_region"
drivers/hwmon/it87.c

 drivers/hwmon/it87.c           |    4 ++++
 drivers/watchdog/it8712f_wdt.c |    9 ++++-----
 drivers/watchdog/it87_wdt.c    |   39 ++++-----------------------------------
 3 files changed, 12 insertions(+), 40 deletions(-)

Signed-off-by Nat Gurumoorthy <[email protected]>

Patch History:
v4:
- Remove extra braces in superio_enter routines.

v3:
- Totally abandon the spinlock based approach and use "request_muxed_region" to hold off requestors if the resource is busy.

v2:
- More verbose patch headers. Add In-Reply-To: field.

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Nat Gurumoorthy

author

2011-04-11 23:52 UTC #1 lore raw

PATCH v4 1/2 Use "request_muxed_region" in it87 watchdog drivers

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 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 <[email protected]>

---

drivers/watchdog/it8712f_wdt.c +4 -5

index 6143f52..5e514bb 100644
@@ -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 */

@@ -123,7 +122,9 @@ static inline void superio_select(int ldn)
 
 static inline void superio_enter(void)
 {
-	spin_lock(&io_lock);
+	while (!request_muxed_region(REG, 2, NAME))
+		continue;
+
 	outb(0x87, REG);
 	outb(0x01, REG);
 	outb(0x55, REG);

@@ -134,7 +135,7 @@ 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)

@@ -382,8 +383,6 @@ static int __init it8712f_wdt_init(void)
 {
 	int err = 0;
 
-	spin_lock_init(&io_lock);
-
 	if (it8712f_wdt_find(&address))
 		return -ENODEV;

drivers/watchdog/it87_wdt.c +4 ~~-35~~

index b1bc72f..a7dfb7c 100644
@@ -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;

@@ -165,6 +164,9 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started, default="
 
 static inline void superio_enter(void)
 {
+	while (!request_muxed_region(REG, 2, WATCHDOG_NAME))
+		continue;
+
 	outb(0x87, REG);
 	outb(0x01, REG);
 	outb(0x55, REG);

@@ -175,6 +177,7 @@ 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 +260,6 @@ 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 +270,10 @@ 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 +284,6 @@ static void wdt_stop(void)
 		superio_outb(0x00, WDTVALMSB);
 
 	superio_exit();
-	spin_unlock_irqrestore(&spinlock, flags);
 }
 
 /**

@@ -303,8 +298,6 @@ 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 +306,12 @@ 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 +330,8 @@ 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 +341,6 @@ 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 +547,13 @@ 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();
 	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 +587,6 @@ static int __init it87_wdt_init(void)
 		return -ENODEV;
 	}
 
-	spin_lock_irqsave(&spinlock, flags);
 	superio_enter();
 
 	superio_select(GPIO);

@@ -621,14 +604,12 @@ 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 +627,6 @@ 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 +640,6 @@ static int __init it87_wdt_init(void)
 		}
 
 		superio_exit();
-		spin_unlock_irqrestore(&spinlock, flags);
 	}
 
 	if (timeout < 1 || timeout > max_units * 60) {

@@ -711,21 +690,17 @@ 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 +708,6 @@ 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 +723,6 @@ 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);

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Alan Cox

2011-04-12 11:41 UTC #2 lore raw

Re: [PATCH v4 1/2] Use "request_muxed_region" in it87 watchdog drivers

drivers/watchdog/it8712f_wdt.c static inline void superio_select(int ldn) · line 127

Quoted 3 lines

drivers/watchdog/it8712f_wdt.c +3 -0

+	while (!request_muxed_region(REG, 2, NAME))
+		continue;
+

This shouldn't need the loop ? - is it only working with the loop present ?

Otherwise this looks good - I'd just like to understand if the loop was needed (indicating a bug has crept into the muxed alloc code somewhere perhaps) or not

Alan

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Natarajan Gurumoorthy

author

2011-04-12 15:46 UTC #3 lore raw

Re: [PATCH v4 1/2] Use "request_muxed_region" in it87 watchdog drivers

Alan,
I looked at your code in kernel/resource.c and I agree the while
is not needed. I guess every time it comes back from "schedule" your code loops back to reserve the region. I will test the code without the while and make the needed change.

Regards
Nat

Quoted 14 lines · Alan Cox

Quoted 3 lines
+ while (!request_muxed_region(REG, 2, NAME))
+ continue;
+
This shouldn't need the loop ? - is it only working with the loop present ?
Otherwise this looks good - I'd just like to understand if the loop was needed (indicating a bug has crept into the muxed alloc code somewhere perhaps) or not
Alan

Signature · 7 lines

Regards
Nat Gurumoorthy AB6SJ

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Nat Gurumoorthy

author

2011-04-11 23:53 UTC #4 lore raw

PATCH v4 2/2 Use "request_muxed_region" in it87 hwmon drivers

In reply to Nat Gurumoorthy

02 - Chages to hwmon it87 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.

Signed-off-by Nat Gurumoorthy <[email protected]>

---

drivers/hwmon/it87.c +4 -0

index 316b648..1dc04d4 100644
@@ -111,6 +111,9 @@ superio_select(int ldn)
 static inline void
 superio_enter(void)
 {
+	while (!request_muxed_region(REG, 2, DRVNAME))
+		continue;
+
 	outb(0x87, REG);
 	outb(0x01, REG);
 	outb(0x55, REG);

@@ -122,6 +125,7 @@ superio_exit(void)
 {
 	outb(0x02, REG);
 	outb(0x02, VAL);
+	release_region(REG, 2);
 }
 
 /* Logical device 4 registers */

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