Re: [PATCH] mach-omap2/powerdomain.c: convert rwsem to rwlock

[Dirk Behme <dirk.behme@xxxxxxxxxxxxxx>]

Paul Walmsley wrote:
> The generic rwsem implementation of down_read() and down_write() does not
> save and restore interrupt state.  This causes powerdomain code to
> inadvertently enable interrupts early in the boot process, causing
> init/main.c to complain.   This patch converts powerdomain locking to
> r-w spinlocks instead.
>
> I'm also curious to know if this fixes the BeagleBoard boot problem.

Yes! :)

Git head is now working on Beagle again.

Many thanks

Dirk


> Signed-off-by: Paul Walmsley <paul@xxxxxxxxx>
> ---
>
>  arch/arm/mach-omap2/powerdomain.c |   46 ++++++++++++++++++++++---------------
>  1 files changed, 27 insertions(+), 19 deletions(-)
>
>
> diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c
> index 939efe4..0a6caaf 100644
> --- a/arch/arm/mach-omap2/powerdomain.c
> +++ b/arch/arm/mach-omap2/powerdomain.c
> @@ -18,7 +18,7 @@
>  #include <linux/module.h>
>  #include <linux/types.h>
>  #include <linux/delay.h>
> -#include <linux/rwsem.h>
> +#include <linux/spinlock.h>
>  #include <linux/list.h>
>  #include <linux/errno.h>
>  #include <linux/err.h>
> @@ -38,10 +38,10 @@
>  static LIST_HEAD(pwrdm_list);
>  
>  /*
> - * pwrdm_rwsem protects pwrdm_list add and del ops - also reused to
> + * pwrdm_rwlock protects pwrdm_list add and del ops - also reused to
>   * protect pwrdm_clkdms[] during clkdm add/del ops
>   */
> -static DECLARE_RWSEM(pwrdm_rwsem);
> +static DEFINE_RWLOCK(pwrdm_rwlock);
>  
>  
>  /* Private functions */
> @@ -131,6 +131,7 @@ void pwrdm_init(struct powerdomain **pwrdm_list)
>   */
>  int pwrdm_register(struct powerdomain *pwrdm)
>  {
> +	unsigned long flags;
>  	int ret = -EINVAL;
>  
>  	if (!pwrdm)
> @@ -139,7 +140,7 @@ int pwrdm_register(struct powerdomain *pwrdm)
>  	if (!omap_chip_is(pwrdm->omap_chip))
>  		return -EINVAL;
>  
> -	down_write(&pwrdm_rwsem);
> +	write_lock_irqsave(&pwrdm_rwlock, flags);
>  	if (_pwrdm_lookup(pwrdm->name)) {
>  		ret = -EEXIST;
>  		goto pr_unlock;
> @@ -151,7 +152,7 @@ int pwrdm_register(struct powerdomain *pwrdm)
>  	ret = 0;
>  
>  pr_unlock:
> -	up_write(&pwrdm_rwsem);
> +	write_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	return ret;
>  }
> @@ -165,12 +166,14 @@ pr_unlock:
>   */
>  int pwrdm_unregister(struct powerdomain *pwrdm)
>  {
> +	unsigned long flags;
> +
>  	if (!pwrdm)
>  		return -EINVAL;
>  
> -	down_write(&pwrdm_rwsem);
> +	write_lock_irqsave(&pwrdm_rwlock, flags);
>  	list_del(&pwrdm->node);
> -	up_write(&pwrdm_rwsem);
> +	write_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	pr_debug("powerdomain: unregistered %s\n", pwrdm->name);
>  
> @@ -187,13 +190,14 @@ int pwrdm_unregister(struct powerdomain *pwrdm)
>  struct powerdomain *pwrdm_lookup(const char *name)
>  {
>  	struct powerdomain *pwrdm;
> +	unsigned long flags;
>  
>  	if (!name)
>  		return NULL;
>  
> -	down_read(&pwrdm_rwsem);
> +	read_lock_irqsave(&pwrdm_rwlock, flags);
>  	pwrdm = _pwrdm_lookup(name);
> -	up_read(&pwrdm_rwsem);
> +	read_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	return pwrdm;
>  }
> @@ -204,7 +208,7 @@ struct powerdomain *pwrdm_lookup(const char *name)
>   *
>   * Call the supplied function for each registered powerdomain.  The
>   * callback function can return anything but 0 to bail out early from
> - * the iterator.  The callback function is called with the pwrdm_rwsem
> + * the iterator.  The callback function is called with the pwrdm_rwlock
>   * held for reading, so no powerdomain structure manipulation
>   * functions should be called from the callback, although hardware
>   * powerdomain control functions are fine.  Returns the last return
> @@ -215,18 +219,19 @@ struct powerdomain *pwrdm_lookup(const char *name)
>  int pwrdm_for_each(int (*fn)(struct powerdomain *pwrdm))
>  {
>  	struct powerdomain *temp_pwrdm;
> +	unsigned long flags;
>  	int ret = 0;
>  
>  	if (!fn)
>  		return -EINVAL;
>  
> -	down_read(&pwrdm_rwsem);
> +	read_lock_irqsave(&pwrdm_rwlock, flags);
>  	list_for_each_entry(temp_pwrdm, &pwrdm_list, node) {
>  		ret = (*fn)(temp_pwrdm);
>  		if (ret)
>  			break;
>  	}
> -	up_read(&pwrdm_rwsem);
> +	read_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	return ret;
>  }
> @@ -243,6 +248,7 @@ int pwrdm_for_each(int (*fn)(struct powerdomain *pwrdm))
>   */
>  int pwrdm_add_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  {
> +	unsigned long flags;
>  	int i;
>  	int ret = -EINVAL;
>  
> @@ -252,7 +258,7 @@ int pwrdm_add_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	pr_debug("powerdomain: associating clockdomain %s with powerdomain "
>  		 "%s\n", clkdm->name, pwrdm->name);
>  
> -	down_write(&pwrdm_rwsem);
> +	write_lock_irqsave(&pwrdm_rwlock, flags);
>  
>  	for (i = 0; i < PWRDM_MAX_CLKDMS; i++) {
>  		if (!pwrdm->pwrdm_clkdms[i])
> @@ -278,7 +284,7 @@ int pwrdm_add_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	ret = 0;
>  
>  pac_exit:
> -	up_write(&pwrdm_rwsem);
> +	write_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	return ret;
>  }
> @@ -295,6 +301,7 @@ pac_exit:
>   */
>  int pwrdm_del_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  {
> +	unsigned long flags;
>  	int ret = -EINVAL;
>  	int i;
>  
> @@ -304,7 +311,7 @@ int pwrdm_del_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	pr_debug("powerdomain: dissociating clockdomain %s from powerdomain "
>  		 "%s\n", clkdm->name, pwrdm->name);
>  
> -	down_write(&pwrdm_rwsem);
> +	write_lock_irqsave(&pwrdm_rwlock, flags);
>  
>  	for (i = 0; i < PWRDM_MAX_CLKDMS; i++)
>  		if (pwrdm->pwrdm_clkdms[i] == clkdm)
> @@ -322,7 +329,7 @@ int pwrdm_del_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	ret = 0;
>  
>  pdc_exit:
> -	up_write(&pwrdm_rwsem);
> +	write_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	return ret;
>  }
> @@ -335,7 +342,7 @@ pdc_exit:
>   * Call the supplied function for each clockdomain in the powerdomain
>   * 'pwrdm'.  The callback function can return anything but 0 to bail
>   * out early from the iterator.  The callback function is called with
> - * the pwrdm_rwsem held for reading, so no powerdomain structure
> + * the pwrdm_rwlock held for reading, so no powerdomain structure
>   * manipulation functions should be called from the callback, although
>   * hardware powerdomain control functions are fine.  Returns -EINVAL
>   * if presented with invalid pointers; or passes along the last return
> @@ -346,18 +353,19 @@ int pwrdm_for_each_clkdm(struct powerdomain *pwrdm,
>  			 int (*fn)(struct powerdomain *pwrdm,
>  				   struct clockdomain *clkdm))
>  {
> +	unsigned long flags;
>  	int ret = 0;
>  	int i;
>  
>  	if (!fn)
>  		return -EINVAL;
>  
> -	down_read(&pwrdm_rwsem);
> +	read_lock_irqsave(&pwrdm_rwlock, flags);
>  
>  	for (i = 0; i < PWRDM_MAX_CLKDMS && !ret; i++)
>  		ret = (*fn)(pwrdm, pwrdm->pwrdm_clkdms[i]);
>  
> -	up_read(&pwrdm_rwsem);
> +	read_unlock_irqrestore(&pwrdm_rwlock, flags);
>  
>  	return ret;
>  }

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