linux-kernel - [PATCH v4 0/2] iio: light: veml6070: add integration time

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Message-Id: <20241031-veml6070-integration-time-v4-0-c66da6788256@gmail.com>
Date: Thu, 31 Oct 2024 00:09:56 +0100
From: Javier Carrasco <javier.carrasco.cruz@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 devicetree@...r.kernel.org, 
 Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: [PATCH v4 0/2] iio: light: veml6070: add integration time

This series adds a missing feature in the veml6070 driver to select the
integration time, which also depends on an external restistor that has
been added to the corresponding bindings.

The datasheet provides a Refresh time vs Rset graph (figure 7), which
does not clearly specify the minimum and maximum values for Rset. The
manufacuter has confirmed that no values under 75 kohms should be used
to keep linearity, and the graph does not go beyond 1200 kohms, which is
also the biggest Rset used in the application note. The default value of
270 kohms is the one currently used in the driver to calculate the UVI.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
---
Changes in v4:
- Add vendor prefix to rset-ohms property (bindings and driver).
- Drop default values for out-of-range rset and fail the probe instead.
- Link to v3: https://lore.kernel.org/r/20241028-veml6070-integration-time-v3-0-dd7ace62f480@gmail.com

Changes in v3:
- veml6075.yaml: simplify property handling (describe it completely at
  the top and add block for the devices that do not support it).
- veml6070.c: use int instead of u32 for the integration times.
- veml6070.c: refactor default rset value assignment.
- veml6070.c: drop comment about default Rset and IT.
- veml6070.c: use units from units.h
- Link to v2: https://lore.kernel.org/r/20241024-veml6070-integration-time-v2-0-d53272ec0feb@gmail.com

Changes in v2:
- Rebase onto iio/testing and drop applied patches.
- veml6075.yaml: use documented -ohms, top-level definition and
  per-device restriction.
- veml6075.yaml: add default value.
- veml6075.yaml: fix typo in commit message.
- veml6070.c: adjust rset property name and convert from ohms to kohms
  to avoid overflows and work with the same units as in the datasheet.
- veml6070.c: change default to 270 kohms (already used as default
  value to calculate UVI).
- veml6070.c: calculate UVI according to the current integration time.
- veml6070.c: re-calculate measurement time (i.e. msleep()) with the
  current integration time.
- Link to v1: https://lore.kernel.org/r/20241017-veml6070-integration-time-v1-0-3507d17d562a@gmail.com

---
Javier Carrasco (2):
      dt-bindings: iio: light: veml6075: document vishay,rset-ohms
      iio: light: veml6070: add support for integration time

 .../bindings/iio/light/vishay,veml6075.yaml        |  18 +++
 drivers/iio/light/veml6070.c                       | 131 +++++++++++++++++++--
 2 files changed, 141 insertions(+), 8 deletions(-)
---
base-commit: e2687d0723257db5025a4cf8cefbd80bed1e2681
change-id: 20241014-veml6070-integration-time-78daf4eaad2f

Best regards,
-- 
Javier Carrasco <javier.carrasco.cruz@...il.com>