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From: "Uwe Kleine-König" <uwe@kleine-koenig.org>
To: Claudiu Beznea <claudiu.beznea@microchip.com>,
	Thierry Reding <thierry.reding@gmail.com>
Cc: linux-pwm@vger.kernel.org,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Ludovic Desroches <ludovic.desroches@microchip.com>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH 4/3] pwm: atmel: document known weaknesses of both hardware and software
Date: Fri, 16 Aug 2019 11:37:48 +0200
Message-ID: <20190816093748.11769-1-uwe@kleine-koenig.org> (raw)
In-Reply-To: <20190815214133.11134-1-uwe@kleine-koenig.org>

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
 drivers/pwm/pwm-atmel.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index 42fe7bc043a8..1ddb93db9627 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -7,6 +7,16 @@
  *
  * Reference manual for "atmel,at91sam9rl-pwm":
  *   http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-11032-32-bit-ARM926EJ-S-Microcontroller-SAM9G25_Datasheet.pdf
+ *
+ * Limitations:
+ * - Periods start with the inactive level.
+ * - Hardware has to be stopped in general to update settings.
+ *
+ * Software bugs/possible improvements:
+ * - When atmel_pwm_apply() is called with state->enabled=false a change in
+ *   state->polarity isn't honored.
+ * - Instead of sleeping to wait for a completed period, the interrupt
+ *   functionality could be used.
  */
 
 #include <linux/clk.h>
-- 
2.20.1


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  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-15 21:41 [PATCH 1/3] pwm: atmel: Add link to reference manual Uwe Kleine-König
2019-08-15 21:41 ` [PATCH 2/3] pwm: atmel: use a constant for maximum prescale value Uwe Kleine-König
2019-08-19  9:27   ` Claudiu.Beznea
2019-08-15 21:41 ` [PATCH 3/3] pwm: atmel: replace loop in prescale calculation by ad-hoc calculation Uwe Kleine-König
2019-08-19  9:27   ` Claudiu.Beznea
2019-08-16  9:37 ` Uwe Kleine-König [this message]
2019-08-16 20:43   ` [PATCH 4/3] pwm: atmel: document known weaknesses of both hardware and software Alexandre Belloni
2019-08-19  8:10     ` Uwe Kleine-König
2019-08-19  9:26   ` Claudiu.Beznea
2019-08-19 10:46     ` Uwe Kleine-König
2019-08-19 12:28       ` Claudiu.Beznea
2019-08-19 15:20         ` Uwe Kleine-König
2019-08-19  9:26 ` [PATCH 1/3] pwm: atmel: Add link to reference manual Claudiu.Beznea
2019-08-19  9:46   ` Nicolas.Ferre

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