Re: [PATCH 47/50] staging: omap-thermal: switch mutex to spinlockinside omap-bandgap

[Eduardo Valentin]

On 16-03-2013 04:59, Dan Carpenter wrote:
> 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@xxxxxx>
> > ---
> >   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.

This IRQ gets masked at the IRQ controller level when served (ONE_SHOT). 
Not sure if your comment is applicable in this case..

> regards,
> dan carpenter

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