/* * Copyright (C) 2011-2013 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #ifndef DRM_PLANE_HELPER_H #define DRM_PLANE_HELPER_H #include #include #include #include /* * Drivers that don't allow primary plane scaling may pass this macro in place * of the min/max scale parameters of the update checker function. * * Due to src being in 16.16 fixed point and dest being in integer pixels, * 1<<16 represents no scaling. */ #define DRM_PLANE_HELPER_NO_SCALING (1<<16) int drm_plane_helper_check_state(struct drm_plane_state *state, const struct drm_rect *clip, int min_scale, int max_scale, bool can_position, bool can_update_disabled); int drm_plane_helper_check_update(struct drm_plane *plane, struct drm_crtc *crtc, struct drm_framebuffer *fb, struct drm_rect *src, struct drm_rect *dest, const struct drm_rect *clip, unsigned int rotation, int min_scale, int max_scale, bool can_position, bool can_update_disabled, bool *visible); int drm_primary_helper_update(struct drm_plane *plane, struct drm_crtc *crtc, struct drm_framebuffer *fb, int crtc_x, int crtc_y, unsigned int crtc_w, unsigned int crtc_h, uint32_t src_x, uint32_t src_y, uint32_t src_w, uint32_t src_h); int drm_primary_helper_disable(struct drm_plane *plane); void drm_primary_helper_destroy(struct drm_plane *plane); extern const struct drm_plane_funcs drm_primary_helper_funcs; int drm_plane_helper_update(struct drm_plane *plane, struct drm_crtc *crtc, struct drm_framebuffer *fb, int crtc_x, int crtc_y, unsigned int crtc_w, unsigned int crtc_h, uint32_t src_x, uint32_t src_y, uint32_t src_w, uint32_t src_h); int drm_plane_helper_disable(struct drm_plane *plane); /* For use by drm_crtc_helper.c */ int drm_plane_helper_commit(struct drm_plane *plane, struct drm_plane_state *plane_state, struct drm_framebuffer *old_fb); #endif ted'>3space:mode:
authorJohn Brooks <john@fastquake.com>2017-01-18 21:50:39 +0000
committerJonathan Cameron <jic23@kernel.org>2017-01-22 13:35:40 +0000
commit5c113b5e0082e90d2e1c7b12e96a7b8cf0623e27 (patch)
treecaf374a799c6c5f8bdf865d7fc0e936e9685f4ca
parentd1aaf20ee655888c227d5137b7a63551f8d15416 (diff)
iio: dht11: Use usleep_range instead of msleep for start signal
The DHT22 (AM2302) datasheet specifies that the LOW start pulse should not exceed 20ms. However, observations with an oscilloscope of an RPi Model 2B (rev 1.1) communicating with a DHT22 sensor showed that the driver was consistently sending start pulses longer than 20ms: Kernel 4.7.10-v7+ (n=132): Minimum pulse length: 20.20ms Maximum: 29.84ms Mean: 24.96ms StDev: 2.82ms Sensor response rate: 100% Read success rate: 76% On kernel 4.8, the start pulse was so long that the sensor would not even respond 97% of the time: Kernel 4.8.16-v7+ (n=100): Minimum pulse length: 30.4ms Maximum: 74.4ms Mean: 39.3ms StDev: 10.2ms Sensor response rate: 3% Read success rate: 3% The driver would return ETIMEDOUT and write log messages like this: [ 51.430987] dht11 dht11@0: Only 1 signal edges detected [ 66.311019] dht11 dht11@0: Only 0 signal edges detected Replacing msleep(18) with usleep_range(18000, 20000) made the pulse length sane again and restored responsiveness: Kernel 4.8.16-v7+ with usleep_range (n=123): Minimum pulse length: 18.16ms Maximum: 20.20ms Mean: 19.85ms StDev: 0.51ms Sensor response rate: 100% Read success rate: 84% Cc: stable@vger.kernel.org Signed-off-by: John Brooks <john@fastquake.com> Reviewed-by: Harald Geyer <harald@ccbib.org> Signed-off-by: Jonathan Cameron <jic23@kernel.org>