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Date: Sun, 4 Jan 2015 17:33:06 -0800
Message-ID: <CAD7vxxL6ZkuODKgZbGq9osURnA3DC7zjHbWr8owG93SVY1h5Bw@mail.gmail.com>
Subject: Re: [PATCH v4 2/3] pwm: kona: Remove setting default smooth type and
 polarity for all channels
From: Tim Kryger <tim.kryger@gmail.com>
To: Jonathan Richardson <jonathar@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>,
        Arun Ramamurthy <arun.ramamurthy@broadcom.com>,
        Thierry Reding <thierry.reding@gmail.com>, Ray Jui <rjui@broadcom.com>,
        bcm-kernel-feedback-list@broadcom.com,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-pwm@vger.kernel.org
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On Sun, Jan 4, 2015 at 5:12 PM, Tim Kryger <tim.kryger@gmail.com> wrote:
> On Tue, Dec 30, 2014 at 2:43 PM, Jonathan Richardson
> <jonathar@broadcom.com> wrote:
>> Setting the default polarity in probe to normal for all channels caused
>> the speaker pwm channel to click. The polarity does need to be set to
>> normal because the hw default is inversed whereas the pwm framework
>> defaults to normal. If a channel is enabled without setting the polarity
>> then the signal would be inversed while linux reports normal. A check
>> is now done prior to enabling the channel to ensure that the hw polarity
>> matches the desired polarity and is changed if there is a discrepency. This
>> prevents unnecessary settings being applied to unused channels but still
>> ensures the correct polarity to be set.
>
> A more direct solution that avoids the potentially undesirable
> consequences of delaying when polarity changes are written to hardware
> would be to update the PWM framework to allow for the registration of
> chips with inversed default polarity.
>
> I will post a patch for your review.

Please see:  https://lkml.org/lkml/2015/1/4/199