From e30a3b780cdec83cdc0bf780e0e0237ee3940d3c Mon Sep 17 00:00:00 2001
From: Young <young.mu@aliyun.com>
Date: Wed, 10 Aug 2016 13:25:43 +0800
Subject: [PATCH] Fix two bugs of tiva pwm lower-half driver impl.
---
arch/arm/src/tiva/tiva_pwm.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/arm/src/tiva/tiva_pwm.c b/arch/arm/src/tiva/tiva_pwm.c
index 8ccaf73837..b5032aeb21 100644
--- a/arch/arm/src/tiva/tiva_pwm.c
+++ b/arch/arm/src/tiva/tiva_pwm.c
@@ -374,9 +374,15 @@ static int tiva_pwm_start(FAR struct pwm_lowerhalf_s *dev,
tiva_pwm_putreg(chan, TIVA_PWMn_LOAD_OFFSET, load - 1);
- /* Configure PWM duty (refer to TM4C1294NC 23.4.8-9) */
+ /* Configure PWM duty (refer to TM4C1294NC 23.4.8-9)
+ *
+ * Workaround:
+ * When comp equals to load, the signal is never pulled down,
+ * so let comp equals to (comp-1)
+ */
uint32_t comp = (uint32_t)((1 - (float)duty / g_pwm_counter) * load);
+ comp = (duty == 0) ? (comp - 1) : (comp);
pwminfo("channel %d: comp = %u (%08x)\n", chan->channel_id, comp, comp);
if (chan->channel_id % 2 == 0)
@@ -394,7 +400,10 @@ static int tiva_pwm_start(FAR struct pwm_lowerhalf_s *dev,
/* Enable PWM channel (refer to TM4C1294NC 23.4.11) */
- putreg32((1 << chan->channel_id), chan->controller_base + TIVA_PWM_ENABLE_OFFSET);
+ uint32_t enable = getreg32(chan->controller_base + TIVA_PWM_ENABLE_OFFSET);
+ enable |= (1 << chan->channel_id);
+ putreg32(enable, chan->controller_base + TIVA_PWM_ENABLE_OFFSET);
+
return OK;
}