[PATCH 00/13] Add Mobileye EyeQ5 support to the Nomadik I2C controller & use hrtimers for timeouts

Théo Lebrun
2024-02-15T16:52:34Z

Hi,

This series adds two tangent features to the Nomadik I2C controller:

- Add a new compatible to support Mobileye EyeQ5 which uses the same IP
block as Nomadik.

It has two quirks to be handled:
- The memory bus only supports 32-bit accesses. A writeb() is used
which we avoid.
- We must write a value into a shared register region (OLB, "Other
Logic Block") depending on the I2C bus speed.

- Allow xfer timeouts below one jiffy by using a workqueue and hrtimers
instead of a completion.

The situation to be addressed is:
- Many devices on the same I2C bus.
- One xfer to each device is sent at regular interval.
- One device gets stuck and does not answer.
- With long timeouts, following devices won't get their message. A
shorter timeout ensures we can still talk to the following
devices.

This clashes a bit with the current i2c_adapter timeout field that
stores a jiffies amount. We cannot rely on it and therefore we take
a value from devicetree as a µs value. If the timeout is less than a
jiffy duration, we switch from standard jiffies timeout to
hrtimers.

There is one patch targeting a hwmon dt-bindings file:
Documentation/devicetree/bindings/hwmon/lm75.yaml. The rest is touching
the I2C bus driver, its bindings and platform devicetrees.

About dependencies:
- The series is based upon v6.8-rc4.
- For testing on EyeQ5 hardware and devicetree patches, we need the
base platform series from Grégory [0].
- The last commit (adding DT phandles for resets), we need the syscon
series [1] that provides the reset controller node.

I think there are discussions to be had about:

- The handling of timeouts. Having a non-jiffy value is not driver
specific. Should this change be done at the subsystem layer? The
subsystem could even fetch the value from devicetree and auto-fill
timeout, with a default given by the driver. Not many drivers seem
to use the i2c_adapter timeout field from my quick grepping.

- The DT prop for timeout. I've picked "timeout-usecs". Some drivers
use vendor prefixes, but this is not vendor-specific and only a
software implementation detail.

- The shape of this series. Initially it was split in two. However I
brought them together as they cannot be applied independently.
Please tell me if a better approach is to be preferred.

Those are thoughts, I'm sure people will have feedback on this.

Have a nice day,
Théo Lebrun

[0]: https://lore.kernel.org/lkml/20240205153503.574468-1-gregory.clement@bootlin.com/
[1]: https://lore.kernel.org/lkml/20240212-mbly-clk-v6-0-c46fa1f93839@bootlin.com/

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
Théo Lebrun (13):
dt-bindings: i2c: nomadik: add timeout-usecs property bindings
dt-bindings: i2c: nomadik: add mobileye,eyeq5-i2c bindings and example
dt-bindings: hwmon: lm75: add label property
i2c: nomadik: rename private struct pointers from dev to priv
i2c: nomadik: simplify IRQ masking logic
i2c: nomadik: use bitops helpers
i2c: nomadik: support short xfer timeouts using waitqueue & hrtimer
i2c: nomadik: replace jiffies by ktime for FIFO flushing timeout
i2c: nomadik: fetch timeout-usecs property from devicetree
i2c: nomadik: support Mobileye EyeQ5 I2C controller
MIPS: mobileye: eyeq5: add 5 I2C controller nodes
MIPS: mobileye: eyeq5: add evaluation board I2C temp sensor
MIPS: mobileye: eyeq5: add resets to I2C controllers

Documentation/devicetree/bindings/hwmon/lm75.yaml | 4 +
.../devicetree/bindings/i2c/st,nomadik-i2c.yaml | 49 +-
arch/mips/boot/dts/mobileye/eyeq5-epm5.dts | 8 +
arch/mips/boot/dts/mobileye/eyeq5.dtsi | 75 +++
drivers/i2c/busses/i2c-nomadik.c | 710 ++++++++++++---------
5 files changed, 534 insertions(+), 312 deletions(-)
---
base-commit: d55aa725e32849f709b61eab3b7a50b810a71a84
change-id: 20231023-mbly-i2c-7c2fbbb1299f

Best regards,
--
Théo Lebrun <theo.lebrun@bootlin.com>