diff options
| author | Martin Peres <martin.peres@labri.fr> | 2012-09-02 01:20:45 (GMT) |
|---|---|---|
| committer | Ben Skeggs <bskeggs@redhat.com> | 2012-10-03 03:13:14 (GMT) |
| commit | bf6546b4219d2b188529f3242efda4048f5b1b41 (patch) | |
| tree | 36c1d3d3c3becdcda11bfdda002dde40b8b2f4aa /drivers/gpu/drm/nouveau/core | |
| parent | aa1b9b4836a8ab093ec06b0780553566a5430da7 (diff) | |
| download | linux-fsl-qoriq-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/drm/nouveau/core')
| -rw-r--r-- | drivers/gpu/drm/nouveau/core/subdev/therm/fan.c | 25 |
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 |