cros_ec: Support the LDO access method used by spring
Add a driver to support the special LDO access used by spring. This is a
custom method in the cros_ec protocol - it does not use an I2C
pass-through.
There are two implementation choices:
1. Write a special LDO driver which can talk across the EC. Duplicate all
the logic from TPS65090 for retrying when the LDO fails to come up.
2. Write a special I2C bus driver which pretends to be a TPS65090 and
transfers reads and writes using the LDO message.
Either is distasteful. The latter method is chosen since it results in less
code duplication and a fairly simple (30-line) implementation of the core
logic.
The crosec 'ldo' subcommand could be removed (since i2c md/mw will work
instead) but is retained as a convenience.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index e861b53..9a62ddd 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -29,6 +29,19 @@
I2C or LPC). Some Chromebooks use this when the hardware design
does not allow direct access to the main PMIC from the AP.
+config I2C_CROS_EC_LDO
+ bool "Provide access to LDOs on the Chrome OS EC"
+ depends on CROS_EC
+ ---help---
+ On many Chromebooks the main PMIC is inaccessible to the AP. This is
+ often dealt with by using an I2C pass-through interface provided by
+ the EC. On some unfortunate models (e.g. Spring) the pass-through
+ is not available, and an LDO message is available instead. This
+ option enables a driver which provides very basic access to those
+ regulators, via the EC. We implement this as an I2C bus which
+ emulates just the TPS65090 messages we know about. This is done to
+ avoid duplicating the logic in the TPS65090 regulator driver for
+ enabling/disabling an LDO.
config DM_I2C_GPIO
bool "Enable Driver Model for software emulated I2C bus driver"