[PATCH v2] ibmaem: Fix 64-bit division on 32-bit platforms

Darrick J. Wong
2008-05-15T21:18:40Z

> To avoid these kind of doubts may I suggest using the time
> conversion definitions of include/linux/time.h?
>
> It would be much easier to understand the intention with
> NSEC_PER_SEC, USEC_PER_SEC etc (comments would also help)

Ok, here's an updated version that makes the conversions a bit clearer.
Tested and run on i386/x86-64.
---
ibmaem: Fix 64-bit division on 32-bit platforms

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---

drivers/hwmon/ibmaem.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/ibmaem.c b/drivers/hwmon/ibmaem.c
index 22fa7d6..3013492 100644
--- a/drivers/hwmon/ibmaem.c
+++ b/drivers/hwmon/ibmaem.c
@@ -31,6 +31,8 @@
#include <linux/idr.h>
#include <linux/sched.h>
#include <linux/platform_device.h>
+#include <linux/math64.h>
+#include <linux/time.h>

#define REFRESH_INTERVAL (HZ)
#define IPMI_TIMEOUT (30 * HZ)
@@ -81,6 +83,7 @@

#define AEM_DEFAULT_POWER_INTERVAL 1000
#define AEM_MIN_POWER_INTERVAL 200
+#define UJ_PER_MJ 1000L

static DEFINE_IDR(aem_idr);
static DEFINE_SPINLOCK(aem_idr_lock);
@@ -841,7 +844,7 @@ static ssize_t aem_show_power(struct device *dev,
{
struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
struct aem_data *data = dev_get_drvdata(dev);
- u64 before, after, time;
+ u64 before, after, delta, time;
signed long leftover;
struct timespec b, a;

@@ -864,9 +867,9 @@ static ssize_t aem_show_power(struct device *dev,
mutex_unlock(&data->lock);

time = timespec_to_ns(&a) - timespec_to_ns(&b);
- time /= 1000;
+ delta = (after - before) * UJ_PER_MJ;

- return sprintf(buf, "%llu\n", (after - before) * 1000000000 / time);
+ return sprintf(buf, "%llu\n", div64_u64(delta * NSEC_PER_SEC, time));
}

/* Display energy use */