From: Gabe Black gabeblack@google.com
First, the "div" value was being used incorrectly to compute the frequency of the PWM timer. The value passed in is a constant which reflects the value that would be found in a configuration register, 0 to 4. That should correspond to a scaling factor of 1, 2, 4, 8, or 16, 1 << div, but div + 1 was being used instead.
Second, the reset value of the timers were being calculated to give an overall frequency, thrown out, and set to a maximum value. This was done so that PWM 4 could be used as the system clock by counting down from a high value, but it was applied indiscriminantly. It should at most be applied only to PWM 4.
This change also takes the opportunity to tidy up the pwm_init function.
Test with command "sf probe 1:0; time sf read 40008000 0 1000". Try with different numbers of bytes and see that sane values are obtained Build and boot U-boot with this patch, backlight works properly.
Signed-off-by: Gabe Black gabeblack@google.com Signed-off-by: Akshay Saraswat akshay.s@samsung.com Acked-by: Simon Glass sjg@chromium.org --- Changes since v2: - None.
Changes since v1: - Added "Acked-by: Simon Glass".
arch/arm/cpu/armv7/s5p-common/pwm.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/arch/arm/cpu/armv7/s5p-common/pwm.c b/arch/arm/cpu/armv7/s5p-common/pwm.c index 3147f59..02156d1 100644 --- a/arch/arm/cpu/armv7/s5p-common/pwm.c +++ b/arch/arm/cpu/armv7/s5p-common/pwm.c @@ -143,7 +143,7 @@ int pwm_init(int pwm_id, int div, int invert) u32 val; const struct s5p_timer *pwm = (struct s5p_timer *)samsung_get_base_timer(); - unsigned long timer_rate_hz; + unsigned long ticks_per_period; unsigned int offset, prescaler;
/* @@ -167,20 +167,24 @@ int pwm_init(int pwm_id, int div, int invert) val |= (div & 0xf) << MUX_DIV_SHIFT(pwm_id); writel(val, &pwm->tcfg1);
- timer_rate_hz = get_pwm_clk() / ((prescaler + 1) * - (div + 1)); + if (pwm_id == 4) { + /* + * TODO(sjg): Use this as a countdown timer for now. We count + * down from the maximum value to 0, then reset. + */ + ticks_per_period = -1UL; + } else { + const unsigned long pwm_hz = 1000; + unsigned long timer_rate_hz = get_pwm_clk() / + ((prescaler + 1) * (1 << div));
- timer_rate_hz = timer_rate_hz / CONFIG_SYS_HZ; + ticks_per_period = timer_rate_hz / pwm_hz; + }
/* set count value */ offset = pwm_id * 3;
- /* - * TODO(sjg): Use this as a countdown timer for now. We count down - * from the maximum value to 0, then reset. - */ - timer_rate_hz = -1; - writel(timer_rate_hz, &pwm->tcntb0 + offset); + writel(ticks_per_period, &pwm->tcntb0 + offset);
val = readl(&pwm->tcon) & ~(0xf << TCON_OFFSET(pwm_id)); if (invert && (pwm_id < 4))