On Fri, Feb 18, 2022 at 10:31:16AM -0800, Bjorn Andersson wrote: > 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@xxxxxxxxx> > Tested-by: Doug Anderson <dianders@xxxxxxxxxxxx> > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> > --- > Changes since v12: > - Initialize ret in lpg_pwm_apply() > > Changes since v11: > - Extended commit message to cover decision to put pwm_chip in the LED driver > - Added Documentation, in particular for the hw_pattern format > - Added a lock to synchronize requests from LED and PWM frameworks > - Turned out that the 9bit selector differs per channel in some PMICs, so > replaced bitmask in lpg_data with lookup based on QPNP SUBTYPE > - Fixed kerneldoc for the struct device pointer in struct lpg > - Rewrote conditional in lut_free() to make it easier to read > - Corrected and deduplicated max_period expression in lpg_calc_freq() > - Extended nom/dom to numerator/denominator in lpg_calc_freq() > - Replaced 1 << 9 with LPG_RESOLUTION in one more place in lpg_calc_freq() > - Use FIELD_PREP() in lpg_apply_freq() as masks was introduced for reading the > same in get_state() > - Cleaned up the pattern format, to allow specifying both low and high pause > with and without pingpong mode. > - Only update frequency and pwm_value if PWM channel is enabled in lpg_pwm_apply > - Make lpg_pwm_get_state() read the hardware state, in order to pick up e.g. > bootloader backlight configuration > - Use devm_bitmap_zalloc() to allocate the lut_bitmap > - Use dev_err_probe() in lpg_probe() > - Extended Kconfig help text to mention module name and satisfy checkpatch > > 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 > > diff --git a/Documentation/leds/leds-qcom-lpg.rst b/Documentation/leds/leds-qcom-lpg.rst > new file mode 100644 > index 000000000000..d4825a289888 > --- /dev/null > +++ b/Documentation/leds/leds-qcom-lpg.rst > @@ -0,0 +1,76 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +============================== > +Kernel driver for Qualcomm LPG > +============================== > + > +Description > +----------- > + > +The Qualcomm LPG can be found in a variety of Qualcomm PMICs and consists of a > +number of PWM channels, a programmable pattern lookup table and a RGB LED > +current sink. > + > +To facilitate the various use cases, the LPG channels can be exposed as > +individual LEDs, grouped together as RGB LEDs or otherwise be accessed as PWM > +channels. The output of each PWM channel is routed to other hardware > +blocks, such as the RGB current sink, GPIO pins etc. > + > +The each PWM channel can operate with a period between 27us and 384 seconds and > +has a 9 bit resolution of the duty cycle. > + > +In order to provide support for status notifications with the CPU subsystem in > +deeper idle states the LPG provides pattern support. This consists of a shared > +lookup table of brightness values and per channel properties to select the > +range within the table to use, the rate and if the pattern should repeat. > + > +The pattern for a channel can be programmed using the "pattern" trigger, using > +the hw_pattern attribute. > + > +/sys/class/leds/<led>/hw_pattern > +-------------------------------- > + > +Specify a hardware pattern for a Qualcomm LPG LED. > + > +The pattern is a series of brightness and hold-time pairs, with the hold-time > +expressed in milliseconds. The hold time is a property of the pattern and must > +therefor be identical for each element in the pattern (except for the pauses > +described below). > + > +Simple pattern:: > + > + "255 500 0 500" > + > + ^ > + | > + 255 +----+ +----+ > + | | | | ... > + 0 | +----+ +---- > + +----------------------> > + 0 5 10 15 time (100ms) you're mixing tabs and spaces here, I suggest to use spaces only. Not sure you want to respin for that. (I didn't look into the rest of the driver, but assume it's fine.) Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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