Date: Tue, 4 Oct 2016 09:48:05 +0200
From: Lukasz Majewski <l.majewski@majess.pl>
To: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>
Cc: <shawnguo@kernel.org>, <thierry.reding@gmail.com>,
        mark.rutland@arm.com, linux-pwm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        stefan@agner.ch, robh+dt@kernel.org, kernel@pengutronix.de,
        fabio.estevam@nxp.com, linux-arm-kernel@lists.infradead.org,
        l.majewski@samsung.com
Subject: Re: [PATCH v2 0/6] Support PWM polarity control
Message-ID: <20161004094805.466ebc6d@jawa>
In-Reply-To: <20161001101235.24598-1-bhuvanchandra.dv@toradex.com>
References: <20161001101235.24598-1-bhuvanchandra.dv@toradex.com>
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Dear Bhuvanchandra,

Thank you for your effort to send those patches to ML.

> Changes since v2:
>=20
> - Picked the stalled patchset[1] from Lothar Wassmann which adds the
> basic support for polarity control on imx-pwm driver and adds
> backward compatibility support for devices which does not have
> polarity control feature.
>=20
> Changes since Lothars v6:
>=20
> - Squash Lukasz patch[2].
>=20
> [1] http://thread.gmane.org/gmane.linux.pwm/1621
> [2] https://www.spinics.net/lists/arm-kernel/msg530818.html
>=20
> Bhuvanchandra DV (3):
>   arm: dts: imx7: Update #pwm-cells for PWM polarity control
>   arm: dts: imx7-colibri: Use pwm polarity control
>   arm: dts: imx7-colibri: Use enable-gpios for BL_ON
>=20
> Lothar Wassmann (3):
>   pwm: print error messages with pr_err() instead of pr_debug()
>   pwm: core: make the PWM_POLARITY flag in DTB optional
>   pwm: imx: support output polarity inversion

For some reason this patchset works differently than the one developed
by Lothar.

The difference is with the brightness level control.

My brightness definition in DTS:

           pwms =3D <&pwm2 0 5000000 PWM_POLARITY_INVERTED>;

 		brightness-levels =3D <  0   1   2   3   4   5   6   7   8   9

					 ..  ............
				    250 251 252 253 254 255>;
		default-brightness-level =3D <50>;
		enable-gpios =3D <&gpio1 2 GPIO_ACTIVE_LOW>;

When I go to the backlight sysfs entry:

cd /sys/devices/soc0/backlight/backlight/backlight

It seems like the brightness level control is inverted - i.e.=20
'echo 20 > brightness" makes picture on the screen very bright, and=20
'echo 200 > brightness' makes the picture diminish.

With my "internal" patches the situation is opposite (and I've checked it w=
ith
my HW connections).

Could you check on your setup if similar situation takes place? I mean
if the brightness control works as expected?

Thanks in advance,
=C5=81ukasz Majewski

>=20
>  Documentation/devicetree/bindings/pwm/imx-pwm.txt |  6 +--
>  arch/arm/boot/dts/imx7-colibri.dtsi               | 12 +++++-
>  arch/arm/boot/dts/imx7s.dtsi                      |  8 ++--
>  drivers/pwm/core.c                                | 31 ++++++++------
>  drivers/pwm/pwm-imx.c                             | 51
> +++++++++++++++++++++-- 5 files changed, 83 insertions(+), 25
> deletions(-)
>=20


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