linux-kernel - Re: [PATCH v13 2/2] leds: Add driver for Qualcomm LPG

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Message-ID: <1645594134-16082-1-git-send-email-quic_c_skakit@quicinc.com>
Date:   Wed, 23 Feb 2022 10:58:54 +0530
From:   Satya Priya <quic_c_skakit@...cinc.com>
To:     <bjorn.andersson@...aro.org>
CC:     <corbet@....net>, <devicetree@...r.kernel.org>,
        <dianders@...omium.org>, <lee.jones@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-leds@...r.kernel.org>,
        <linux-pwm@...r.kernel.org>, <luca@...tu.xyz>, <pavel@....cz>,
        <robh+dt@...nel.org>, <thierry.reding@...il.com>,
        <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v13 2/2] leds: Add driver for Qualcomm LPG

From: Bjorn Andersson <bjorn.andersson@...aro.org>

The Light Pulse Generator (LPG) is a PWM-block found in a wide range of
PMICs from Qualcomm. These PMICs typically comes with 1-8 LPG instances,
with their output being routed to various other components, such as
current sinks or GPIOs.

Each LPG instance can operate on fixed parameters or based on a shared
lookup-table, altering the duty cycle over time. This provides the means
for hardware assisted transitions of LED brightness.

A typical use case for the fixed parameter mode is to drive a PWM
backlight control signal, the driver therefor allows each LPG instance
to be exposed to the kernel either through the LED framework or the PWM
framework.

A typical use case for the LED configuration is to drive RGB LEDs in
smartphones etc, for which the driver supports multiple channels to be
ganged up to a MULTICOLOR LED. In this configuration the pattern
generators will be synchronized, to allow for multi-color patterns.

The idea of modelling this as a LED driver ontop of a PWM driver was
considered, but setting the properties related to patterns does not fit
in the PWM API. Similarly the idea of just duplicating the lower bits in
a PWM and LED driver separately was considered, but this would not allow
the PWM channels and LEDs to be configured on a per-board basis. The
driver implements the more complex LED interface, and provides a PWM
interface on the side of that, in the same driver.

Tested-by: Luca Weiss <luca@...tu.xyz>
Tested-by: Doug Anderson <dianders@...omium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
---

Tested-by: Satya Priya <quic_c_skakit@...cinc.com>

 Documentation/leds/leds-qcom-lpg.rst |   76 ++
 drivers/leds/Kconfig                 |    3 +
 drivers/leds/Makefile                |    3 +
 drivers/leds/rgb/Kconfig             |   18 +
 drivers/leds/rgb/Makefile            |    3 +
 drivers/leds/rgb/leds-qcom-lpg.c     | 1401 ++++++++++++++++++++++++++++++++++
 6 files changed, 1504 insertions(+)
 create mode 100644 Documentation/leds/leds-qcom-lpg.rst
 create mode 100644 drivers/leds/rgb/Kconfig
 create mode 100644 drivers/leds/rgb/Makefile
 create mode 100644 drivers/leds/rgb/leds-qcom-lpg.c