[PATCH v7 4/7] pwm: ntxec: Add driver for PWM function in Netronix EC

[Lee Jones]

On Mon, 11 Jan 2021, Thierry Reding wrote:

> On Sat, Jan 09, 2021 at 07:02:17PM +0100, Jonathan Neuschäfer wrote:
> > The Netronix EC provides a PWM output which is used for the backlight
> > on some ebook readers. This patches adds a driver for the PWM output.
> > 
> > The .get_state callback is not implemented, because the PWM state can't
> > be read back from the hardware.
> > 
> > Signed-off-by: Jonathan Neuschäfer <j.neuschaefer at gmx.net>
> > ---
> > v7:
> > - no changes
> > 
> > v6:
> > - https://lore.kernel.org/lkml/20201208011000.3060239-5-j.neuschaefer@gmx.net/
> > - Move period / duty cycle setting code to a function
> > - Rename pwmchip_to_priv to ntxec_pwm_from_chip
> > - Set period and duty cycle only before enabling the output
> > - Mention that duty=0, enable=1 is assumed not to happen
> > - Interleave writes to the period and duty cycle registers, to minimize the
> >   window of time that an inconsistent state is configured
> > 
> > v5:
> > - https://lore.kernel.org/lkml/20201201011513.1627028-5-j.neuschaefer@gmx.net/
> > - Avoid truncation of period and duty cycle to 32 bits
> > - Make ntxec_pwm_ops const
> > - Use regmap_multi_reg_write
> > - Add comment about get_state to ntxec_pwm_ops
> > - Add comments about non-atomicity of (period, duty cycle) update
> > 
> > v4:
> > - https://lore.kernel.org/lkml/20201122222739.1455132-5-j.neuschaefer@gmx.net/
> > - Document hardware/driver limitations
> > - Only accept normal polarity
> > - Fix a typo ("zone" -> "zero")
> > - change MAX_PERIOD_NS to 0xffff * 125
> > - Clamp period to the maximum rather than returning an error
> > - Rename private struct pointer to priv
> > - Rearrage control flow in _probe to save a few lines and a temporary variable
> > - Add missing MODULE_ALIAS line
> > - Spell out ODM
> > 
> > v3:
> > - https://lore.kernel.org/lkml/20200924192455.2484005-5-j.neuschaefer@gmx.net/
> > - Relicense as GPLv2 or later
> > - Add email address to copyright line
> > - Remove OF compatible string and don't include linux/of_device.h
> > - Fix bogus ?: in return line
> > - Don't use a comma after sentinels
> > - Avoid ret |= ... pattern
> > - Move 8-bit register conversion to ntxec.h
> > 
> > v2:
> > - https://lore.kernel.org/lkml/20200905133230.1014581-6-j.neuschaefer@gmx.net/
> > - Various grammar and style improvements, as suggested by Uwe Kleine-König,
> >   Lee Jones, and Alexandre Belloni
> > - Switch to regmap
> > - Prefix registers with NTXEC_REG_
> > - Add help text to the Kconfig option
> > - Use the .apply callback instead of the old API
> > - Add a #define for the time base (125ns)
> > - Don't change device state in .probe; this avoids multiple problems
> > - Rework division and overflow check logic to perform divisions in 32 bits
> > - Avoid setting duty cycle to zero, to work around a hardware quirk
> > ---
> >  drivers/pwm/Kconfig     |   8 ++
> >  drivers/pwm/Makefile    |   1 +
> >  drivers/pwm/pwm-ntxec.c | 182 ++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 191 insertions(+)
> >  create mode 100644 drivers/pwm/pwm-ntxec.c
> 
> Lee, I assume you'll want to pick the whole set up into the MFD tree? If
> so:

Yes, I'll pick this up once we have all the Acks.

The Arm parts usually go in separately.

> Acked-by: Thierry Reding <thierry.reding at gmail.com>

Thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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