diff options
| author | Duncan Laurie <dlaurie@chromium.org> | 2015-11-12 16:33:03 -0800 |
|---|---|---|
| committer | chrome-bot <chrome-bot@chromium.org> | 2015-11-13 15:28:23 -0800 |
| commit | 43a4578a9b1b2f21a91c3747a29cca33bd27698c (patch) | |
| tree | 4f10823e51c89595e2947bacffc2e6f979599e46 | |
| parent | 467fe2836e0d37bda6c216c40ced6456313468f2 (diff) | |
| download | chrome-ec-43a4578a9b1b2f21a91c3747a29cca33bd27698c.tar.gz | |
pwm: Add option for alternate clock source
The PWM clock on some chips can be configured to use different
sources, which will have a dramatic effect on the actual PWM
frequency. In order to support a variety of devices attached
to PWM outputs add an option to select an alternate source.
This is then implemented on the mec1322 chip to use the 100kHz
clock source for PWM which will allow it to drive a keyboard
backlight at appropriate frequencies.
BUG=chrome-os-partner:47435
BRANCH=none
TEST=verify that kblight brightness can be changed on chell
Change-Id: Ibe93a8e029baae5a2d5f520d590b0cc4ab9a7f93
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/312509
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>
| -rw-r--r-- | chip/mec1322/pwm.c | 11 | ||||
| -rw-r--r-- | include/pwm.h | 5 |
2 files changed, 13 insertions, 3 deletions
diff --git a/chip/mec1322/pwm.c b/chip/mec1322/pwm.c index d66c03da05..1643664855 100644 --- a/chip/mec1322/pwm.c +++ b/chip/mec1322/pwm.c @@ -44,11 +44,15 @@ int pwm_get_duty(enum pwm_channel ch) return MEC1322_PWM_ON(pwm_channels[ch].channel); } -static void pwm_configure(int ch, int active_low) +static void pwm_configure(int ch, int active_low, int clock_low) { + /* + * clock_low=0 selects the 48MHz Ring Oscillator source + * clock_low=1 selects the 100kHz_Clk source + */ MEC1322_PWM_CFG(ch) = (15 << 3) | /* Pre-divider = 16 */ (active_low ? (1 << 2) : 0) | - (0 << 1); /* 48M clock */ + (clock_low ? (1 << 1) : 0); } static void pwm_init(void) @@ -57,7 +61,8 @@ static void pwm_init(void) for (i = 0; i < PWM_CH_COUNT; ++i) { pwm_configure(pwm_channels[i].channel, - pwm_channels[i].flags & PWM_CONFIG_ACTIVE_LOW); + pwm_channels[i].flags & PWM_CONFIG_ACTIVE_LOW, + pwm_channels[i].flags & PWM_CONFIG_ALT_CLOCK); pwm_set_duty(i, 0); } } diff --git a/include/pwm.h b/include/pwm.h index c4ae331b1c..66610b9240 100644 --- a/include/pwm.h +++ b/include/pwm.h @@ -41,5 +41,10 @@ int pwm_get_duty(enum pwm_channel ch); * its duty cycle to produce a given fan RPM. */ #define PWM_CONFIG_HAS_RPM_MODE (1 << 1) +/** + * PWM clock select alternate source. The actual clock and alternate + * source are chip dependent. + */ +#define PWM_CONFIG_ALT_CLOCK (1 << 2) #endif /* __CROS_EC_PWM_H */ |