linux-kernel - Re: [PATCH 47/50] staging: omap-thermal: switch mutex to spinlock inside omap-bandgap

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Date:	Sat, 16 Mar 2013 11:59:02 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Eduardo Valentin <eduardo.valentin@...com>
Cc:	gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH 47/50] staging: omap-thermal: switch mutex to spinlock
 inside omap-bandgap

On Fri, Mar 15, 2013 at 09:00:35AM -0400, Eduardo Valentin wrote:
> Because there is a need to lock inside IRQ handler, this patch
> changes the locking mechanism inside the omap-bandgap.[c,h] to
> spinlocks. Now this lock is used to protect omap_bandgap struct
> during APIs exposed (possibly used in sysfs handling functions)
> and inside the ALERT IRQ handler.
> 
> Because there are registers shared among the sensors, this lock
> is global, not per sensor.
> 
> Signed-off-by: Eduardo Valentin <eduardo.valentin@...com>
> ---
>  drivers/staging/omap-thermal/TODO           |    1 -
>  drivers/staging/omap-thermal/omap-bandgap.c |   18 ++++++++++--------
>  drivers/staging/omap-thermal/omap-bandgap.h |    4 ++--
>  3 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/staging/omap-thermal/TODO b/drivers/staging/omap-thermal/TODO
> index 77b761b..0f24e9b 100644
> --- a/drivers/staging/omap-thermal/TODO
> +++ b/drivers/staging/omap-thermal/TODO
> @@ -1,7 +1,6 @@
>  List of TODOs (by Eduardo Valentin)
>  
>  on omap-bandgap.c:
> -- Rework locking
>  - Improve driver code by adding usage of regmap-mmio
>  - Test every exposed API to userland
>  - Add support to hwmon
> diff --git a/drivers/staging/omap-thermal/omap-bandgap.c b/drivers/staging/omap-thermal/omap-bandgap.c
> index 4b631fd..846ced6 100644
> --- a/drivers/staging/omap-thermal/omap-bandgap.c
> +++ b/drivers/staging/omap-thermal/omap-bandgap.c
> @@ -33,7 +33,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/err.h>
>  #include <linux/types.h>
> -#include <linux/mutex.h>
> +#include <linux/spinlock.h>
>  #include <linux/reboot.h>
>  #include <linux/of_device.h>
>  #include <linux/of_platform.h>
> @@ -170,6 +170,7 @@ static irqreturn_t omap_bandgap_talert_irq_handler(int irq, void *data)
>  	u32 t_hot = 0, t_cold = 0, ctrl;
>  	int i;
>  
> +	spin_lock(&bg_ptr->lock);
>  	for (i = 0; i < bg_ptr->conf->sensor_count; i++) {
>  		tsr = bg_ptr->conf->sensors[i].registers;
>  		ctrl = omap_bandgap_readl(bg_ptr, tsr->bgap_status);
> @@ -208,6 +209,7 @@ static irqreturn_t omap_bandgap_talert_irq_handler(int irq, void *data)
>  		if (bg_ptr->conf->report_temperature)
>  			bg_ptr->conf->report_temperature(bg_ptr, i);
>  	}
> +	spin_unlock(&bg_ptr->lock);
>  
>  	return IRQ_HANDLED;
>  }
> @@ -502,9 +504,9 @@ int _omap_bandgap_write_threshold(struct omap_bandgap *bg_ptr, int id, int val,
>  	if (ret < 0)
>  		goto exit;
>  
> -	mutex_lock(&bg_ptr->bg_mutex);
> +	spin_lock(&bg_ptr->lock);

These need to disable interrupts because we take the spin lock in
the IRQ handler.

regards,
dan carpenter


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