gpio: Add a way to read 3-way strapping pins
Using the internal vs. external pull resistors it is possible to get
27 different combinations from 3 strapping pins. Add an implementation
of this.
This involves updating the sandbox GPIO driver to model external and
(weaker) internal pull resistors. The get_value() method now takes account
of what is driving a pin:
sandbox: GPIOD_EXT_DRIVEN - in which case GPIO_EXT_HIGH provides the
value
outside source - in which case GPIO_EXT_PULL_UP/DOWN indicates the
external state and we work the final state using those flags and
the internal GPIOD_PULL_UP/DOWN flags
Of course the outside source does not really exist in sandbox. We are just
modelling it for test purpose.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/include/asm/gpio.h b/arch/sandbox/include/asm/gpio.h
index 33b83ea..9e10052 100644
--- a/arch/sandbox/include/asm/gpio.h
+++ b/arch/sandbox/include/asm/gpio.h
@@ -26,8 +26,11 @@
/* Our own private GPIO flags, which musn't conflict with GPIOD_... */
#define GPIOD_EXT_HIGH BIT(31) /* external source is high (else low) */
#define GPIOD_EXT_DRIVEN BIT(30) /* external source is driven */
+#define GPIOD_EXT_PULL_UP BIT(29) /* GPIO has external pull-up */
+#define GPIOD_EXT_PULL_DOWN BIT(28) /* GPIO has external pull-down */
-#define GPIOD_SANDBOX_MASK GENMASK(31, 30)
+#define GPIOD_EXT_PULL (BIT(28) | BIT(29))
+#define GPIOD_SANDBOX_MASK GENMASK(31, 28)
/**
* Return the simulated value of a GPIO (used only in sandbox test code)