diff options
author | Gabe Black <gabeblack@google.com> | 2013-03-28 08:32:18 +0400 |
---|---|---|
committer | Minkyu Kang <mk7.kang@samsung.com> | 2013-04-01 09:02:08 +0400 |
commit | c059f274ade1a5f7d1f39927d8b31a41cba9034c (patch) | |
tree | f1b87289d425e6b2696bbd5aebe0e5048537b914 /arch/arm/cpu/armv7/s5p-common | |
parent | f24869d3a8f6646c2d207057719e6fa0a8f31eb0 (diff) | |
download | u-boot-c059f274ade1a5f7d1f39927d8b31a41cba9034c.tar.xz |
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/arm/cpu/armv7/s5p-common')
-rw-r--r-- | arch/arm/cpu/armv7/s5p-common/pwm.c | 24 |
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 3147f59e57..02156d184e 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)) |