Date:   Thu, 28 Apr 2022 09:42:22 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        Luca Weiss <luca@...tu.xyz>, Rob Herring <robh+dt@...nel.org>,
        Jonathan Corbet <corbet@....net>, linux-leds@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-pwm <linux-pwm@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v14 2/2] leds: Add driver for Qualcomm LPG

Hi Pavel,

On Wed, Apr 6, 2022 at 8:18 AM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi Pavel,
>
> On Thu, Mar 3, 2022 at 2:10 PM Doug Anderson <dianders@...omium.org> wrote:
> >
> > Hi,
> >
> > On Thu, Mar 3, 2022 at 1:41 PM Bjorn Andersson
> > <bjorn.andersson@...aro.org> 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.
> > >
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > ---
> > >
> > > Changes since v13:
> > > - Fixed mixed space/tab indentation in documentation
> > > - Added 0 as to lpg_clk_rates[] to match the hardware state, to avoid + 1 in
> > >   lpg_apply_freq() and - 1 in lpg_pwm_get_state()
> > > - Don't divide with 0 if current clock is 0 in lpg_pwm_get_state(), just return
> > >   period = duty = 0 in this case
> > > - Renamed "clk" in struct lpg_channel to clk_sel
> > > - Renamed "pre_div" in struct lpg_channel to pre_div_sel
> > >
> > > 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     | 1405 ++++++++++++++++++++++++++
> > >  6 files changed, 1508 insertions(+)
> >
> > Gets rid of the KASAN error and PWM still works for me, so happy to add back:
> >
> > Tested-by: Douglas Anderson <dianders@...omium.org>
> >
> > I haven't done a full review of the driver but I did a once-over of
> > the changes between v12 and v13 and they look good to me.
>
> With v5.18-rc1 released, this seems like it would be an ideal time to
> land this driver and its bindings in a for-next branch for the leds
> subsystem. Is there anything blocking it? Are you the right person to
> land them? Ideally the bindings / driver (patch #1 and #2) from
> Satya's series [1] could land right atop it since it's ready too?
>
> [1] https://lore.kernel.org/r/1645509309-16142-1-git-send-email-quic_c_skakit@quicinc.com/

I don't mean to be a huge pest, but we're already at v5.18-rc4 (almost
at -rc5) and these two series are still pending. I'm worried that
we're going to miss the window to land them again. Can you give any
update about them?

Thanks!

-Doug

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