lkml.org 
[lkml]   [2019]   [May]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 14/14] pwm: meson: add documentation to the driver
    From
    Date
    On 25/05/2019 20:11, Martin Blumenstingl wrote:
    > Add a link to the datasheet and a short summary how the hardware works.
    > The goal is to make it easier for other developers to understand why the
    > pwm-meson driver is implemented the way it is.
    >
    > Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
    > Co-authored-by: Neil Armstrong <narmstrong@baylibre.com>
    > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
    > ---
    > drivers/pwm/pwm-meson.c | 18 ++++++++++++++++++
    > 1 file changed, 18 insertions(+)
    >
    > diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
    > index bb48ba85f756..6a978caba483 100644
    > --- a/drivers/pwm/pwm-meson.c
    > +++ b/drivers/pwm/pwm-meson.c
    > @@ -1,5 +1,23 @@
    > // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
    > /*
    > + * PWM controller driver for Amlogic Meson SoCs.
    > + *
    > + * This PWM is only a set of Gates, Dividers and Counters:
    > + * PWM output is achieved by calculating a clock that permits calculating
    > + * two periods (low and high). The counter then has to be set to switch after
    > + * N cycles for the first half period.
    > + * The hardware has no "polarity" setting. This driver reverses the period
    > + * cycles (the low length is inverted with the high length) for
    > + * PWM_POLARITY_INVERSED. This means that .get_state cannot read the polarity
    > + * from the hardware.
    > + * Setting the duty cycle will disable and re-enable the PWM output.
    > + * Disabling the PWM stops the output immediately (without waiting for the
    > + * current period to complete first).
    > + *
    > + * The public S922X datasheet contains some documentation for this PWM
    > + * controller starting on page 1084:
    > + * https://dl.khadas.com/Hardware/VIM2/Datasheet/S912_Datasheet_V0.220170314publicversion-Wesion.pdf
    > + *
    > * Copyright (c) 2016 BayLibre, SAS.
    > * Author: Neil Armstrong <narmstrong@baylibre.com>
    > * Copyright (C) 2014 Amlogic, Inc.
    >

    Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

    \
     
     \ /
      Last update: 2019-05-27 14:34    [W:4.093 / U:0.172 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site