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authorGabe Black <gabeblack@google.com>2013-03-28 04:32:18 +0000
committerMinkyu Kang <mk7.kang@samsung.com>2013-04-01 14:02:08 +0900
commitc059f274ade1a5f7d1f39927d8b31a41cba9034c (patch)
treef1b87289d425e6b2696bbd5aebe0e5048537b914 /arch
parentf24869d3a8f6646c2d207057719e6fa0a8f31eb0 (diff)
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Exynos: pwm: Fix two bugs in the exynos pwm configuration code
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> Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/cpu/armv7/s5p-common/pwm.c24
1 files 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))