From: Jerome Brunet <jbrunet@baylibre.com>
To: "Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Thierry Reding <thierry.reding@gmail.com>,
Neil Armstrong <neil.armstrong@linaro.org>,
Kevin Hilman <khilman@baylibre.com>,
linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-amlogic@lists.infradead.org,
Munehisa Kamata <kamatam@amazon.com>,
kernel@pengutronix.de
Subject: Re: [PATCH] pwm: meson: Explicitly set .polarity in .get_state()
Date: Mon, 13 Mar 2023 10:07:48 +0100 [thread overview]
Message-ID: <1ja60h106q.fsf@starbuckisacylon.baylibre.com> (raw)
In-Reply-To: <CAFBinCCfqgBkHq2fFy=d+8C6nwq=wehu9nzePfwuY5ndfLMWoQ@mail.gmail.com>
On Sat 11 Mar 2023 at 22:00, Martin Blumenstingl <martin.blumenstingl@googlemail.com> wrote:
> Hi Uwe,
>
> On Fri, Mar 10, 2023 at 8:14 PM Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> [...]
>> There is a complicating fact, that the .apply() callback fakes support
>> for inversed polarity. This is not (and cannot) be matched by
>> .get_state(). As fixing this isn't easy, only point it out in a comment
>> to prevent authors of other drivers from copying that approach.
> If you have any suggestions on how to fix this then please let us know.
> I don't recall any board needing support for inverted PWM - but they
> may be out there somewhere...
AFAIK, PWM are essentially used for the SDIO 32k clock and voltage
regulators. I don't recall seeing anything else.
It should be safe to change polarity if necessary, except for the DVFS
PWM regulators maybe ? I fear that if we change the PWM setting it might
trigger a glitch on the supply and possibly stall the CPU.
That being said, I don't think there is any particular care regarding
that right now, so maybe it is fine.
>
>> Fixes: c375bcbaabdb ("pwm: meson: Read the full hardware state in meson_pwm_get_state()")
>> Reported-by: Munehisa Kamata <kamatam@amazon.com>
>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
>
>
> Best regards,
> Martin
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next prev parent reply other threads:[~2023-03-13 9:16 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-10 19:14 Uwe Kleine-König
2023-03-11 21:00 ` Martin Blumenstingl
2023-03-11 21:44 ` Uwe Kleine-König
2023-03-12 20:22 ` Martin Blumenstingl
2023-03-13 9:07 ` Jerome Brunet [this message]
2023-03-13 9:51 ` Uwe Kleine-König
2023-03-13 19:54 ` Martin Blumenstingl
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