linux-kernel - [PATCH v3 2/5] pwm: omap-dmtimer: Update description for pwm omap dm timer

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Message-ID: <20200312042210.17344-3-lokeshvutla@ti.com>
Date:   Thu, 12 Mar 2020 09:52:07 +0530
From:   Lokesh Vutla <lokeshvutla@...com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
CC:     Tony Lindgren <tony@...mide.com>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pwm@...r.kernel.org>,
        Sekhar Nori <nsekhar@...com>, Vignesh R <vigneshr@...com>,
        Lokesh Vutla <lokeshvutla@...com>
Subject: [PATCH v3 2/5] pwm: omap-dmtimer: Update description for pwm omap dm timer

Update the description with a brief about how pwm is generated
using OMAP DM timer and add Limitations for the pwm generations.
Also add link to the Reference Manual.

Suggested-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Acked-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@...com>
---
 drivers/pwm/pwm-omap-dmtimer.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
index e4f5f710bfaa..92aac6c86b95 100644
--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/drivers/pwm/pwm-omap-dmtimer.c
@@ -10,7 +10,15 @@
  *
  * Description:
  *   This file is the core OMAP support for the generic, Linux
- *   PWM driver / controller, using the OMAP's dual-mode timers.
+ *   PWM driver / controller, using the OMAP's dual-mode timers
+ *   with a timer counter that goes up. When it overflows it gets
+ *   reloaded with the load value and the pwm output goes up.
+ *   When counter matches with match register, the output goes down.
+ *   Reference Manual: http://www.ti.com/lit/ug/spruh73q/spruh73q.pdf
+ *
+ * Limitations:
+ * - When PWM is stopped, timer counter gets stopped immediately. This
+ *   doesn't allow the current PWM period to complete and stops abruptly.
  */
 
 #include <linux/clk.h>
-- 
2.23.0