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authorMartin Peres <martin.peres@labri.fr>2012-09-02 01:20:45 (GMT)
committerBen Skeggs <bskeggs@redhat.com>2012-10-03 03:13:14 (GMT)
commitbf6546b4219d2b188529f3242efda4048f5b1b41 (patch)
tree36c1d3d3c3becdcda11bfdda002dde40b8b2f4aa /drivers/gpu
parentaa1b9b4836a8ab093ec06b0780553566a5430da7 (diff)
downloadlinux-bf6546b4219d2b188529f3242efda4048f5b1b41.tar.xz
drm/nouveau/fan: rewrite the fan tachometer driver to get more precision, faster
The previous driver waited for 250ms to accumulate data. This version times a complete fan rotation and extrapolates to RPM. The fan rotational speed should now be read in less than 250ms (worst case) and usually in less 50ms. Signed-off-by: Martin Peres <martin.peres@labri.fr> Reviewed-by: Ben Skeggs <bskeggs@redhat.com> Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/nouveau/core/subdev/therm/fan.c25
1 files changed, 16 insertions, 9 deletions
diff --git a/drivers/gpu/drm/nouveau/core/subdev/therm/fan.c b/drivers/gpu/drm/nouveau/core/subdev/therm/fan.c
index 9ad6e16..b7339b5 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/therm/fan.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/therm/fan.c
@@ -105,30 +105,37 @@ nouveau_therm_fan_sense(struct nouveau_therm *therm)
struct nouveau_gpio *gpio = nouveau_gpio(therm);
struct dcb_gpio_func func;
u32 cycles, cur, prev;
- u64 start;
+ u64 start, end, tach;
if (gpio->find(gpio, 0, DCB_GPIO_FAN_SENSE, 0xff, &func))
return -ENODEV;
- /* Monitor the GPIO input 0x3b for 250ms.
+ /* Time a complete rotation and extrapolate to RPM:
* When the fan spins, it changes the value of GPIO FAN_SENSE.
- * We get 4 changes (0 -> 1 -> 0 -> 1 -> [...]) per complete rotation.
+ * We get 4 changes (0 -> 1 -> 0 -> 1) per complete rotation.
*/
start = ptimer->read(ptimer);
prev = gpio->get(gpio, 0, func.func, func.line);
cycles = 0;
do {
+ usleep_range(500, 1000); /* supports 0 < rpm < 7500 */
+
cur = gpio->get(gpio, 0, func.func, func.line);
if (prev != cur) {
+ if (!start)
+ start = ptimer->read(ptimer);
cycles++;
prev = cur;
}
-
- usleep_range(500, 1000); /* supports 0 < rpm < 7500 */
- } while (ptimer->read(ptimer) - start < 250000000);
-
- /* interpolate to get rpm */
- return cycles / 4 * 4 * 60;
+ } while (cycles < 5 && ptimer->read(ptimer) - start < 250000000);
+ end = ptimer->read(ptimer);
+
+ if (cycles == 5) {
+ tach = (u64)60000000000;
+ do_div(tach, (end - start));
+ return tach;
+ } else
+ return 0;
}
static void