On Mon, 11 Jan 2021, Thierry Reding wrote:

On Sat, Jan 09, 2021 at 07:02:17PM +0100, Jonathan Neuschäfer wrote:

quoted

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@gmx.net>
---
v7:
- no changes

v6:
- https://lore.kernel.org/lkml/20201208011000.3060239-5-j.neuschaefer@gmx.net/ (local)
- 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/ (local)
- 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/ (local)
- 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/ (local)
- 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/ (local)
- 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 <redacted>

Thanks.

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