Re: [PATCH v10 2/2] leds: Add driver for Qualcomm LPG

Marijn Suijten
2022-02-02T10:17:12Z

On 2022-01-28 18:53:24, Bjorn Andersson wrote:
> On Wed 27 Oct 16:27 CDT 2021, Marijn Suijten wrote:
>
> > On 2021-10-27 23:19:30, Marijn Suijten wrote:
> > > Hi Bjorn,
> > >
> > > On 2021-10-22 10:25:35, Bjorn Andersson wrote:
> > > > On Sat 09 Oct 21:39 PDT 2021, 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 support 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.
> > > > >
> > > > > Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> > > > > ---
> > > >
> > > > Any feedback on this?
> > >
> > > I asked in #linux-msm whether anything is wrong with the patterns,
> > > since my Sony Discovery (sdm630 with a pm660l) blinks way quicker on a
> > > pattern that's supposed to stay on for 1s and off for 1s:
> > >
> > > echo "0 1000 255 1000" > /sys/class/leds/rgb\:status/hw_pattern
> > >
> > > It however seems to be broken in the same way on an older version now
> > > (this might be v9 or v8) which I don't remember to be the case. Can you
> > > double-check if this is all working fine on your side? If so, I'll have
> > > to find some time to debug it on my end.
> > >
> > > Thanks!
> > > - Marijn
> >
> > Another thing I just ran into: on both patch revisions the colors are
> > flipped. multi_index reports "red green glue", but the values written
> > to multi_intensity correspond to "blue green red" instead. Is it the
> > same on your side?
> >
>
> I booted one of my 8974 devices with RGB LED and the colors matches my
> expectations. Can you confirm that your mapping in the DT node is
> correct?
>
> E.g. with pm8941 the mapping should be "backwards":
> [snip]

Thanks, this was indeed a mistake on my side: downstream pm660l sets
blue to the first channel too, whereas I set it to red. Let's blame it
on downstream mixing zero-based and one-based indices and my inability
to read that :)

- Marijn