Thread (28 messages) 28 messages, 5 authors, 2016-03-08
STALE3734d

[PATCH 1/4] pwm: omap-dmtimer: fix inaccurate period/duty_cycle calculation

From: Thierry Reding <hidden>
Date: 2016-03-04 15:17:48
Also in: linux-omap, linux-pwm

On Fri, Jan 29, 2016 at 11:26:51PM -0500, David Rivshin (Allworx) wrote:
From: David Rivshin <redacted>

Fix the calculation of load_value and match_value. Currently they
are slightly too low, which produces a noticeably wrong PWM rate with
sufficiently short periods (i.e. when 1/period approaches clk_rate/2).

Example:
 clk_rate=32768Hz, period=122070ns, duty_cycle=61035ns (8192Hz/50% PWM)
 Correct values: load = 0xfffffffc, match = 0xfffffffd
 Current values: load = 0xfffffffa, match = 0xfffffffc
 effective PWM: period=183105ns, duty_cycle=91553ns (5461Hz/50% PWM)

Fixes: 6604c6556db9 ("pwm: Add PWM driver for OMAP using dual-mode timers")
Signed-off-by: David Rivshin <redacted>
---
 drivers/pwm/pwm-omap-dmtimer.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)
Applied, thanks.

Thierry
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