X-Git-Url: http://git.cascardo.eti.br/?a=blobdiff_plain;f=drivers%2Fpwm%2Fpwm-omap-dmtimer.c;h=b7e6ecba7d5c23422323acb4dfa6c6fe432a3a29;hb=2edeb8540bc21247906e13ad2a08317d6fa410e7;hp=826634ec0d5c0ca26d4b09b18247ed25860dea68;hpb=1c3d770043583d99118d52cad309f586ef8e7d4a;p=cascardo%2Flinux.git

diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
index 826634ec0d5c..b7e6ecba7d5c 100644
--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/drivers/pwm/pwm-omap-dmtimer.c
@@ -31,6 +31,7 @@
 #include <linux/time.h>
 
 #define DM_TIMER_LOAD_MIN 0xfffffffe
+#define DM_TIMER_MAX      0xffffffff
 
 struct pwm_omap_dmtimer_chip {
 	struct pwm_chip chip;
@@ -46,13 +47,9 @@ to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
 	return container_of(chip, struct pwm_omap_dmtimer_chip, chip);
 }
 
-static int pwm_omap_dmtimer_calc_value(unsigned long clk_rate, int ns)
+static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
 {
-	u64 c = (u64)clk_rate * ns;
-
-	do_div(c, NSEC_PER_SEC);
-
-	return DM_TIMER_LOAD_MIN - c;
+	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
 }
 
 static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
@@ -99,12 +96,14 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
 				   int duty_ns, int period_ns)
 {
 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
-	int load_value, match_value;
+	u32 period_cycles, duty_cycles;
+	u32 load_value, match_value;
 	struct clk *fclk;
 	unsigned long clk_rate;
 	bool timer_active;
 
-	dev_dbg(chip->dev, "duty cycle: %d, period %d\n", duty_ns, period_ns);
+	dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n",
+		duty_ns, period_ns);
 
 	mutex_lock(&omap->mutex);
 	if (duty_ns == pwm_get_duty_cycle(pwm) &&
@@ -117,15 +116,13 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
 	fclk = omap->pdata->get_fclk(omap->dm_timer);
 	if (!fclk) {
 		dev_err(chip->dev, "invalid pmtimer fclk\n");
-		mutex_unlock(&omap->mutex);
-		return -EINVAL;
+		goto err_einval;
 	}
 
 	clk_rate = clk_get_rate(fclk);
 	if (!clk_rate) {
 		dev_err(chip->dev, "invalid pmtimer fclk rate\n");
-		mutex_unlock(&omap->mutex);
-		return -EINVAL;
+		goto err_einval;
 	}
 
 	dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);
@@ -133,11 +130,51 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
 	/*
 	 * Calculate the appropriate load and match values based on the
 	 * specified period and duty cycle. The load value determines the
-	 * cycle time and the match value determines the duty cycle.
+	 * period time and the match value determines the duty time.
+	 *
+	 * The period lasts for (DM_TIMER_MAX-load_value+1) clock cycles.
+	 * Similarly, the active time lasts (match_value-load_value+1) cycles.
+	 * The non-active time is the remainder: (DM_TIMER_MAX-match_value)
+	 * clock cycles.
+	 *
+	 * NOTE: It is required that: load_value <= match_value < DM_TIMER_MAX
+	 *
+	 * References:
+	 *   OMAP4430/60/70 TRM sections 22.2.4.10 and 22.2.4.11
+	 *   AM335x Sitara TRM sections 20.1.3.5 and 20.1.3.6
 	 */
-	load_value = pwm_omap_dmtimer_calc_value(clk_rate, period_ns);
-	match_value = pwm_omap_dmtimer_calc_value(clk_rate,
-						  period_ns - duty_ns);
+	period_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, period_ns);
+	duty_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, duty_ns);
+
+	if (period_cycles < 2) {
+		dev_info(chip->dev,
+			 "period %d ns too short for clock rate %lu Hz\n",
+			 period_ns, clk_rate);
+		goto err_einval;
+	}
+
+	if (duty_cycles < 1) {
+		dev_dbg(chip->dev,
+			"duty cycle %d ns is too short for clock rate %lu Hz\n",
+			duty_ns, clk_rate);
+		dev_dbg(chip->dev, "using minimum of 1 clock cycle\n");
+		duty_cycles = 1;
+	} else if (duty_cycles >= period_cycles) {
+		dev_dbg(chip->dev,
+			"duty cycle %d ns is too long for period %d ns at clock rate %lu Hz\n",
+			duty_ns, period_ns, clk_rate);
+		dev_dbg(chip->dev, "using maximum of 1 clock cycle less than period\n");
+		duty_cycles = period_cycles - 1;
+	}
+
+	dev_dbg(chip->dev, "effective duty cycle: %lld ns, period: %lld ns\n",
+		DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * duty_cycles,
+				      clk_rate),
+		DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * period_cycles,
+				      clk_rate));
+
+	load_value = (DM_TIMER_MAX - period_cycles) + 1;
+	match_value = load_value + duty_cycles - 1;
 
 	/*
 	 * We MUST stop the associated dual-mode timer before attempting to
@@ -166,6 +203,11 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
 	mutex_unlock(&omap->mutex);
 
 	return 0;
+
+err_einval:
+	mutex_unlock(&omap->mutex);
+
+	return -EINVAL;
 }
 
 static int pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip,