sandbox: cros-ec: Add tests for the Chromium OS EC PWM driver

This patch adds a limited pulse-width modulator to sandbox's Chromium OS
Embedded Controller emulation. The emulated PWM device supports multiple
channels but can only set a duty cycle for each, as the actual EC
doesn't expose any functionality or information other than that. Though
the EC supports specifying the PWM channel by its type (e.g. display
backlight, keyboard backlight), this is not implemented in the emulation
as nothing in U-Boot uses this type specification.

This emulated PWM device is then used to test the Chromium OS PWM driver
in sandbox. Adding the required device node to the sandbox test
device-tree unfortunately makes it the first PWM device, so this also
touches some other tests to make sure they still use the sandbox PWM.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 8e7eaf2..d85bb46 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -139,6 +139,12 @@
 				size = <0x10000>;
 			};
 		};
+
+		cros_ec_pwm: cros-ec-pwm {
+			compatible = "google,cros-ec-pwm";
+			#pwm-cells = <1>;
+		};
+
 	};
 
 	dsi_host: dsi_host {
diff --git a/arch/sandbox/include/asm/test.h b/arch/sandbox/include/asm/test.h
index 1cb960a..dab1a4e 100644
--- a/arch/sandbox/include/asm/test.h
+++ b/arch/sandbox/include/asm/test.h
@@ -275,4 +275,14 @@
  */
 void sandbox_cros_ec_set_test_flags(struct udevice *dev, uint flags);
 
+/**
+ * sandbox_cros_ec_get_pwm_duty() - Get EC PWM config for testing purposes
+ *
+ * @dev: Device to check
+ * @index: PWM channel index
+ * @duty: Current duty cycle in 0..EC_PWM_MAX_DUTY range.
+ * @return 0 if OK, -ENOSPC if the PWM number is invalid
+ */
+int sandbox_cros_ec_get_pwm_duty(struct udevice *dev, uint index, uint *duty);
+
 #endif