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 v2 4/6] pwm: atmel: document known weaknesses of both hardware and software
Date: Sat, 24 Aug 2019 02:10:39 +0200 [thread overview]
Message-ID: <20190824001041.11007-5-uwe@kleine-koenig.org> (raw)
In-Reply-To: <20190824001041.11007-1-uwe@kleine-koenig.org>
This documents the my findings while reading through the driver and the
reference manual.
Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
Changes since (implicit) v1 sent with Message-Id:
20190816093748.11769-1-uwe@kleine-koenig.org:
- Add some prosa to commit log
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 3786ab9db5cf..89f3a62f7541 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -7,6 +7,16 @@
*
* Links to reference manuals for the supported PWM chips can be found in
* Documentation/arm/microchip.rst.
+ *
+ * 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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next prev parent reply other threads:[~2019-08-24 0:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-24 0:10 [PATCH v2 0/6] Updates for the atmel PWM driver Uwe Kleine-König
2019-08-24 0:10 ` [PATCH v2 1/6] pwm: atmel: Add a hint where to find hardware documentation Uwe Kleine-König
2019-08-26 8:19 ` Nicolas.Ferre
2019-08-24 0:10 ` [PATCH v2 2/6] pwm: atmel: use a constant for maximum prescale value Uwe Kleine-König
2019-08-24 0:10 ` [PATCH v2 3/6] pwm: atmel: replace loop in prescale calculation by ad-hoc calculation Uwe Kleine-König
2019-08-24 0:10 ` Uwe Kleine-König [this message]
2019-08-24 0:10 ` [PATCH v2 5/6] pwm: atmel: use atmel_pwm_writel in atmel_pwm_ch_writel; ditto for readl Uwe Kleine-König
2019-08-24 0:10 ` [PATCH v2 6/6] pwm: atmel: implement .get_state() Uwe Kleine-König
2019-08-28 10:26 ` Claudiu.Beznea
2019-09-02 20:06 ` Uwe Kleine-König
2019-10-24 7:30 ` [PATCH v2 0/6] Updates for the atmel PWM driver Uwe Kleine-König
2020-01-08 13:00 ` Thierry Reding
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