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Date: Tue, 10 May 2011 19:52:07 -0700
From: Guenter Roeck <guenter.roeck@...csson.com>
To: Nat Gurumoorthy <natg@...gle.com>
CC: Jean Delvare <khali@...ux-fr.org>,
Wim Van Sebroeck <wim@...ana.be>,
"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"mikew@...gle.com" <mikew@...gle.com>
Subject: Re: [PATCH v10 1/2] Use "request_muxed_region" in it87 watchdog
drivers
On Mon, May 09, 2011 at 02:45:07PM -0400, Nat Gurumoorthy wrote:
> 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.
>
> "superio_enter" will return an error if call to "request_muxed_region" fails.
> Rest of the code change is to ripple an error return from superio_enter to
> the top level.
>
> Signed-off-by: Nat Gurumoorthy <natg@...gle.com>
One comment inline below; ok with me but others may have concerns.
Acked-by: Guenter Roeck <guenter.roeck@...csson.com>
> ---
>
> diff --git a/drivers/watchdog/it8712f_wdt.c b/drivers/watchdog/it8712f_wdt.c
> index 6143f52..c8677ac 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 */
> @@ -121,20 +120,27 @@ static inline void superio_select(int ldn)
> outb(ldn, VAL);
> }
>
> -static inline void superio_enter(void)
> +static inline int
> +superio_enter(void)
> {
> - spin_lock(&io_lock);
> + /*
> + * Try to reserve REG and REG + 1 for exclusive access.
> + */
> + if (!request_muxed_region(REG, 2, NAME))
> + return -EBUSY;
> +
> outb(0x87, REG);
> outb(0x01, REG);
> outb(0x55, REG);
> outb(0x55, REG);
> + return 0;
> }
>
> 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)
> @@ -173,10 +179,13 @@ static int it8712f_wdt_get_status(void)
> return 0;
> }
>
> -static void it8712f_wdt_enable(void)
> +static int it8712f_wdt_enable(void)
> {
> + int ret = superio_enter();
> + if (ret)
> + return ret;
> +
> printk(KERN_DEBUG NAME ": enabling watchdog timer\n");
> - superio_enter();
> superio_select(LDN_GPIO);
>
> superio_outb(wdt_control_reg, WDT_CONTROL);
> @@ -186,13 +195,17 @@ static void it8712f_wdt_enable(void)
> superio_exit();
>
> it8712f_wdt_ping();
> +
> + return 0;
> }
>
> -static void it8712f_wdt_disable(void)
> +static int it8712f_wdt_disable(void)
> {
> - printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> - superio_enter();
> + printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
> superio_select(LDN_GPIO);
>
> superio_outb(0, WDT_CONFIG);
> @@ -202,6 +215,7 @@ static void it8712f_wdt_disable(void)
> superio_outb(0, WDT_TIMEOUT);
>
> superio_exit();
> + return 0;
> }
>
> static int it8712f_wdt_notify(struct notifier_block *this,
> @@ -252,6 +266,7 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
> WDIOF_MAGICCLOSE,
> };
> int value;
> + int ret;
>
> switch (cmd) {
> case WDIOC_GETSUPPORT:
> @@ -259,7 +274,9 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
> return -EFAULT;
> return 0;
> case WDIOC_GETSTATUS:
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> superio_select(LDN_GPIO);
>
> value = it8712f_wdt_get_status();
> @@ -280,7 +297,9 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
> if (value > (max_units * 60))
> return -EINVAL;
> margin = value;
> - superio_enter();
> + ret = superio_enter();
> + if (ret)
> + return ret;
> superio_select(LDN_GPIO);
>
> it8712f_wdt_update_margin();
> @@ -299,10 +318,14 @@ static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
>
> static int it8712f_wdt_open(struct inode *inode, struct file *file)
> {
> + int ret;
> /* only allow one at a time */
> if (test_and_set_bit(0, &wdt_open))
> return -EBUSY;
> - it8712f_wdt_enable();
> +
> + ret = it8712f_wdt_enable();
> + if (ret)
> + return ret;
> return nonseekable_open(inode, file);
> }
>
> @@ -313,7 +336,8 @@ static int it8712f_wdt_release(struct inode *inode, struct file *file)
> ": watchdog device closed unexpectedly, will not"
> " disable the watchdog timer\n");
> } else if (!nowayout) {
> - it8712f_wdt_disable();
> + if (it8712f_wdt_disable())
> + printk(KERN_WARNING NAME "Watchdog disable failed\n");
> }
> expect_close = 0;
> clear_bit(0, &wdt_open);
> @@ -340,8 +364,10 @@ static int __init it8712f_wdt_find(unsigned short *address)
> {
> int err = -ENODEV;
> int chip_type;
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> - superio_enter();
> chip_type = superio_inw(DEVID);
> if (chip_type != IT8712F_DEVID)
> goto exit;
> @@ -382,8 +408,6 @@ static int __init it8712f_wdt_init(void)
> {
> int err = 0;
>
> - spin_lock_init(&io_lock);
> -
> if (it8712f_wdt_find(&address))
> return -ENODEV;
>
> @@ -392,7 +416,11 @@ static int __init it8712f_wdt_init(void)
> return -EBUSY;
> }
>
> - it8712f_wdt_disable();
> + err = it8712f_wdt_disable();
> + if (err) {
> + printk(KERN_ERR NAME ": unable to disable watchdog timer.\n");
> + goto out;
> + }
>
> err = register_reboot_notifier(&it8712f_wdt_notifier);
> if (err) {
> diff --git a/drivers/watchdog/it87_wdt.c b/drivers/watchdog/it87_wdt.c
> index b1bc72f..e3c03a9 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;
> @@ -163,18 +162,27 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started, default="
>
> /* Superio Chip */
>
> -static inline void superio_enter(void)
> +static inline int
> +superio_enter(void)
> {
> + /*
> + * Try to reserve REG and REG + 1 for exclusive access.
> + */
> + if (!request_muxed_region(REG, 2, WATCHDOG_NAME))
> + return -EBUSY;
> +
> outb(0x87, REG);
> outb(0x01, REG);
> outb(0x55, REG);
> outb(0x55, REG);
> + return 0;
> }
>
> static inline void superio_exit(void)
> {
> outb(0x02, REG);
> outb(0x02, VAL);
> + release_region(REG, 2);
> }
>
> static inline void superio_select(int ldn)
> @@ -255,12 +263,11 @@ static void wdt_keepalive(void)
> set_bit(WDTS_KEEPALIVE, &wdt_status);
> }
>
> -static void wdt_start(void)
> +static int wdt_start(void)
> {
> - unsigned long flags;
> -
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> superio_select(GPIO);
> if (test_bit(WDTS_USE_GP, &wdt_status))
> @@ -270,15 +277,15 @@ static void wdt_start(void)
> wdt_update_timeout();
>
> superio_exit();
> - spin_unlock_irqrestore(&spinlock, flags);
> +
> + return 0;
> }
>
> -static void wdt_stop(void)
> +static int wdt_stop(void)
> {
> - unsigned long flags;
> -
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
>
> superio_select(GPIO);
> superio_outb(0x00, WDTCTRL);
> @@ -288,7 +295,7 @@ static void wdt_stop(void)
> superio_outb(0x00, WDTVALMSB);
>
> superio_exit();
> - spin_unlock_irqrestore(&spinlock, flags);
> + return 0;
> }
>
> /**
> @@ -303,8 +310,6 @@ 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 +318,15 @@ 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();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
> +
> superio_select(GPIO);
> wdt_update_timeout();
> superio_exit();
> }
> - spin_unlock_irqrestore(&spinlock, flags);
> return 0;
> }
>
> @@ -339,12 +345,12 @@ 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();
> + int ret = superio_enter();
> + if (ret)
> + return ret;
> +
> superio_select(GPIO);
> if (superio_inb(WDTCTRL) & WDT_ZERO) {
> superio_outb(0x00, WDTCTRL);
> @@ -353,7 +359,6 @@ 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;
> @@ -379,9 +384,17 @@ static int wdt_open(struct inode *inode, struct file *file)
> if (exclusive && test_and_set_bit(WDTS_DEV_OPEN, &wdt_status))
> return -EBUSY;
> if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
> + int ret;
> if (nowayout && !test_and_set_bit(WDTS_LOCKED, &wdt_status))
> __module_get(THIS_MODULE);
> - wdt_start();
> +
> + ret = wdt_start();
> + if (ret) {
> + clear_bit(WDTS_LOCKED, &wdt_status);
> + clear_bit(WDTS_TIMER_RUN, &wdt_status);
> + clear_bit(WDTS_DEV_OPEN, &wdt_status);
> + return ret;
> + }
> }
> return nonseekable_open(inode, file);
> }
> @@ -403,7 +416,16 @@ static int wdt_release(struct inode *inode, struct file *file)
> {
> if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
> if (test_and_clear_bit(WDTS_EXPECTED, &wdt_status)) {
> - wdt_stop();
> + int ret = wdt_stop();
> + if (ret) {
> + /*
> + * Stop failed. Just keep the watchdog alive
> + * and hope nothing bad happens.
> + */
> + set_bit(WDTS_EXPECTED, &wdt_status);
> + wdt_keepalive();
> + return ret;
> + }
> clear_bit(WDTS_TIMER_RUN, &wdt_status);
> } else {
> wdt_keepalive();
> @@ -484,7 +506,9 @@ static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> &ident, sizeof(ident)) ? -EFAULT : 0;
>
> case WDIOC_GETSTATUS:
> - wdt_get_status(&status);
> + rc = wdt_get_status(&status);
> + if (rc)
> + return rc;
> return put_user(status, uarg.i);
>
> case WDIOC_GETBOOTSTATUS:
> @@ -500,14 +524,22 @@ static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>
> switch (new_options) {
> case WDIOS_DISABLECARD:
> - if (test_bit(WDTS_TIMER_RUN, &wdt_status))
> - wdt_stop();
> + if (test_bit(WDTS_TIMER_RUN, &wdt_status)) {
> + rc = wdt_stop();
> + if (rc)
> + return rc;
> + }
> clear_bit(WDTS_TIMER_RUN, &wdt_status);
> return 0;
>
> case WDIOS_ENABLECARD:
> - if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status))
> - wdt_start();
> + if (!test_and_set_bit(WDTS_TIMER_RUN, &wdt_status)) {
> + rc = wdt_start();
> + if (rc) {
> + clear_bit(WDTS_TIMER_RUN, &wdt_status);
> + return rc;
> + }
> + }
> return 0;
>
> default:
> @@ -560,16 +592,17 @@ static int __init it87_wdt_init(void)
> int rc = 0;
> int try_gameport = !nogameport;
> u8 chip_rev;
> - unsigned long flags;
> + int gp_rreq_fail = 0;
>
> wdt_status = 0;
>
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + rc = superio_enter();
> + if (rc)
> + return rc;
> +
> chip_type = superio_inw(CHIPID);
> chip_rev = superio_inb(CHIPREV) & 0x0f;
> superio_exit();
> - spin_unlock_irqrestore(&spinlock, flags);
>
> switch (chip_type) {
> case IT8702_ID:
> @@ -603,8 +636,9 @@ static int __init it87_wdt_init(void)
> return -ENODEV;
> }
>
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
> + rc = superio_enter();
> + if (rc)
> + return rc;
>
> superio_select(GPIO);
> superio_outb(WDT_TOV1, WDTCFG);
> @@ -620,21 +654,16 @@ 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);
> + gp_rreq_fail = 1;
> }
>
> /* If we haven't Gameport support, try to get CIR support */
> if (!test_bit(WDTS_USE_GP, &wdt_status)) {
> if (!request_region(CIR_BASE, 8, WATCHDOG_NAME)) {
> - if (rc == -EIO)
> + if (gp_rreq_fail)
> printk(KERN_ERR PFX
> "I/O Address 0x%04x and 0x%04x"
> " already in use\n", base, CIR_BASE);
> @@ -646,21 +675,16 @@ static int __init it87_wdt_init(void)
> goto err_out;
> }
> base = CIR_BASE;
> - spin_lock_irqsave(&spinlock, flags);
> - superio_enter();
>
> superio_select(CIR);
> superio_outw(base, BASEREG);
> superio_outb(0x00, CIR_ILS);
> ciract = superio_inb(ACTREG);
> superio_outb(0x01, ACTREG);
> - if (rc == -EIO) {
> + if (gp_rreq_fail) {
> superio_select(GAMEPORT);
> superio_outb(gpact, ACTREG);
> }
> -
> - superio_exit();
This is one possible solution; we'll have to see if the maintainer
accepts it. There may be some concerns about blocking superio
access during the calls to register_reboot_notifier() and misc_register().
> - spin_unlock_irqrestore(&spinlock, flags);
> }
>
> if (timeout < 1 || timeout > max_units * 60) {
> @@ -704,6 +728,7 @@ static int __init it87_wdt_init(void)
> "nogameport=%d)\n", chip_type, chip_rev, timeout,
> nowayout, testmode, exclusive, nogameport);
>
> + superio_exit();
> return 0;
>
> err_out_reboot:
> @@ -711,49 +736,37 @@ 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);
> }
>
> + superio_exit();
> return rc;
> }
>
> 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);
> - superio_outb(0x00, WDTCFG);
> - superio_outb(0x00, WDTVALLSB);
> - if (max_units > 255)
> - superio_outb(0x00, WDTVALMSB);
> - if (test_bit(WDTS_USE_GP, &wdt_status)) {
> - superio_select(GAMEPORT);
> - superio_outb(gpact, ACTREG);
> - } else {
> - superio_select(CIR);
> - superio_outb(ciract, ACTREG);
> + if (superio_enter() == 0) {
> + superio_select(GPIO);
> + superio_outb(0x00, WDTCTRL);
> + superio_outb(0x00, WDTCFG);
> + superio_outb(0x00, WDTVALLSB);
> + if (max_units > 255)
> + superio_outb(0x00, WDTVALMSB);
> + if (test_bit(WDTS_USE_GP, &wdt_status)) {
> + superio_select(GAMEPORT);
> + superio_outb(gpact, ACTREG);
> + } else {
> + superio_select(CIR);
> + superio_outb(ciract, ACTREG);
> + }
> + superio_exit();
> }
> - superio_exit();
> - if (!nolock)
> - spin_unlock_irqrestore(&spinlock, flags);
>
> misc_deregister(&wdt_miscdev);
> unregister_reboot_notifier(&wdt_notifier);
--
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