linux-kernel - [PATCH] pwm: meson: compute cnt register value in proper way

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Date:   Fri, 2 Jun 2023 13:32:11 +0300
From:   George Stark <gnstark@...rdevices.ru>
To:     <thierry.reding@...il.com>, <u.kleine-koenig@...gutronix.de>,
        <neil.armstrong@...aro.org>, <khilman@...libre.com>,
        <jbrunet@...libre.com>, <martin.blumenstingl@...glemail.com>,
        <hkallweit1@...il.com>
CC:     <linux-iio@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-amlogic@...ts.infradead.org>, <kernel@...rdevices.ru>,
        George Stark <GNStark@...rdevices.ru>,
        Dmitry Rokosov <ddrokosov@...rdevices.ru>
Subject: [PATCH] pwm: meson: compute cnt register value in proper way

According to the datasheet, the PWM high and low clock count values
should be set to at least one. Therefore, setting the clock count
register to 0 actually means 1 clock count.

Signed-off-by: George Stark <GNStark@...rdevices.ru>
Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
---
This patch is based on currently unmerged patch by Heiner Kallweit
https://lore.kernel.org/linux-amlogic/23fe625e-dc23-4db8-3dce-83167cd3b206@gmail.com
---
diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
index 834acd7..57e7d9c 100644
--- a/drivers/pwm/pwm-meson.c
+++ b/drivers/pwm/pwm-meson.c
@@ -206,6 +206,11 @@
 		channel->pre_div = pre_div;
 		channel->hi = duty_cnt;
 		channel->lo = cnt - duty_cnt;
+
+		if (channel->hi)
+			channel->hi--;
+		if (channel->lo)
+			channel->lo--;
 	}
 
 	return 0;
@@ -340,7 +345,8 @@
 	channel->lo = FIELD_GET(PWM_LOW_MASK, value);
 	channel->hi = FIELD_GET(PWM_HIGH_MASK, value);
 
-	state->period = meson_pwm_cnt_to_ns(chip, pwm, channel->lo + channel->hi);
+	state->period = meson_pwm_cnt_to_ns(chip, pwm,
+					    channel->lo + 1 + channel->hi + 1);
 	state->duty_cycle = meson_pwm_cnt_to_ns(chip, pwm, channel->hi);
 
 	return 0;