[v2,4/6] pwm: atmel: document known weaknesses of both hardware and software
diff mbox series

Message ID 20190824001041.11007-5-uwe@kleine-koenig.org
State New
Headers show
Series
  • Updates for the atmel PWM driver
Related show

Commit Message

Uwe Kleine-König Aug. 24, 2019, 12:10 a.m. UTC
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(+)

Patch
diff mbox series

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>