From: Thierry Reding <thierry.reding@gmail.com>
To: "David Rivshin (Allworx)" <drivshin.allworx@gmail.com>
Cc: linux-pwm@vger.kernel.org,
Neil Armstrong <narmstrong@baylibre.com>,
linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
Tony Lindgren <tony@atomide.com>,
Grant Erickson <marathon96@gmail.com>, NeilBrown <neilb@suse.de>,
Joachim Eastwood <manabian@gmail.com>
Subject: Re: [PATCH 1/4] pwm: omap-dmtimer: fix inaccurate period/duty_cycle calculation
Date: Fri, 4 Mar 2016 16:17:48 +0100 [thread overview]
Message-ID: <20160304151748.GD26400@ulmo.nvidia.com> (raw)
In-Reply-To: <1454128014-22866-2-git-send-email-drivshin.allworx@gmail.com>
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On Fri, Jan 29, 2016 at 11:26:51PM -0500, David Rivshin (Allworx) wrote:
> From: David Rivshin <drivshin@allworx.com>
>
> 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 <drivshin@allworx.com>
> ---
> drivers/pwm/pwm-omap-dmtimer.c | 27 ++++++++++++++++++++-------
> 1 file changed, 20 insertions(+), 7 deletions(-)
Applied, thanks.
Thierry
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WARNING: multiple messages have this Message-ID (diff)
From: thierry.reding@gmail.com (Thierry Reding)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/4] pwm: omap-dmtimer: fix inaccurate period/duty_cycle calculation
Date: Fri, 4 Mar 2016 16:17:48 +0100 [thread overview]
Message-ID: <20160304151748.GD26400@ulmo.nvidia.com> (raw)
In-Reply-To: <1454128014-22866-2-git-send-email-drivshin.allworx@gmail.com>
On Fri, Jan 29, 2016 at 11:26:51PM -0500, David Rivshin (Allworx) wrote:
> From: David Rivshin <drivshin@allworx.com>
>
> 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 <drivshin@allworx.com>
> ---
> drivers/pwm/pwm-omap-dmtimer.c | 27 ++++++++++++++++++++-------
> 1 file changed, 20 insertions(+), 7 deletions(-)
Applied, thanks.
Thierry
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next prev parent reply other threads:[~2016-03-04 15:17 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-30 4:26 [PATCH 0/4] pwm: omap-dmtimer: fix period/duty_cycle calculation David Rivshin (Allworx)
2016-01-30 4:26 ` David Rivshin (Allworx)
2016-01-30 4:26 ` [PATCH 1/4] pwm: omap-dmtimer: fix inaccurate " David Rivshin (Allworx)
2016-01-30 4:26 ` David Rivshin (Allworx)
2016-02-03 10:23 ` Neil Armstrong
2016-02-03 10:23 ` Neil Armstrong
2016-02-15 20:24 ` Adam Ford
2016-02-15 20:24 ` Adam Ford
2016-03-04 15:17 ` Thierry Reding [this message]
2016-03-04 15:17 ` Thierry Reding
2016-01-30 4:26 ` [PATCH 2/4] pwm: omap-dmtimer: add sanity checking for load and match values David Rivshin (Allworx)
2016-01-30 4:26 ` David Rivshin (Allworx)
2016-02-01 18:35 ` David Rivshin (Allworx)
2016-02-01 18:35 ` David Rivshin (Allworx)
2016-02-03 10:24 ` Neil Armstrong
2016-02-03 10:24 ` Neil Armstrong
2016-01-30 4:26 ` [PATCH 3/4] pwm: omap-dmtimer: round load and match values rather than truncate David Rivshin (Allworx)
2016-01-30 4:26 ` David Rivshin (Allworx)
2016-02-03 10:24 ` Neil Armstrong
2016-02-03 10:24 ` Neil Armstrong
2016-03-04 15:18 ` Thierry Reding
2016-03-04 15:18 ` Thierry Reding
2016-01-30 4:26 ` [PATCH 4/4] pwm: omap-dmtimer: add dev_dbg() message for effective period and duty cycle David Rivshin (Allworx)
2016-01-30 4:26 ` David Rivshin (Allworx)
2016-01-30 14:51 ` Neil Armstrong
2016-01-30 14:51 ` Neil Armstrong
2016-02-01 18:22 ` David Rivshin (Allworx)
2016-02-01 18:22 ` David Rivshin (Allworx)
2016-02-01 18:59 ` Tony Lindgren
2016-02-01 18:59 ` Tony Lindgren
2016-02-02 16:23 ` Thierry Reding
2016-02-02 16:23 ` Thierry Reding
2016-02-02 23:44 ` David Rivshin (Allworx)
2016-02-02 23:44 ` David Rivshin (Allworx)
2016-02-03 14:14 ` Thierry Reding
2016-02-03 14:14 ` Thierry Reding
2016-02-05 19:51 ` David Rivshin (Allworx)
2016-02-05 19:51 ` David Rivshin (Allworx)
2016-02-05 19:51 ` David Rivshin (Allworx)
2016-02-09 12:49 ` Neil Armstrong
2016-02-09 12:49 ` Neil Armstrong
2016-01-30 14:52 ` [PATCH 0/4] pwm: omap-dmtimer: fix period/duty_cycle calculation Neil Armstrong
2016-01-30 14:52 ` Neil Armstrong
2016-02-01 20:14 ` David Rivshin (Allworx)
2016-02-01 20:14 ` David Rivshin (Allworx)
2016-02-27 1:31 ` David Rivshin (Allworx)
2016-02-27 1:31 ` David Rivshin (Allworx)
2016-03-04 15:19 ` Thierry Reding
2016-03-04 15:19 ` Thierry Reding
2016-03-04 16:27 ` David Rivshin (Allworx)
2016-03-04 16:27 ` David Rivshin (Allworx)
2016-03-04 16:29 ` Adam Ford
2016-03-04 20:01 ` David Rivshin (Allworx)
2016-03-04 20:01 ` David Rivshin (Allworx)
2016-03-04 20:03 ` Adam Ford
2016-03-04 20:03 ` Adam Ford
2016-03-04 21:18 ` Thierry Reding
2016-03-04 21:18 ` Thierry Reding
2016-03-04 23:20 ` David Rivshin (Allworx)
2016-03-04 23:20 ` David Rivshin (Allworx)
2016-03-08 23:23 ` Adam Ford
2016-03-08 23:23 ` Adam Ford
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