dm: sandbox: pwm: Add a basic pwm test

Unfortunately a test for the PWM uclass was not included when it was
submitted. This was noticed when trying to add more functionality:

   http://patchwork.ozlabs.org/patch/748172/

Add a simple test to get us started.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pwm/sandbox_pwm.c b/drivers/pwm/sandbox_pwm.c
new file mode 100644
index 0000000..c2ce974
--- /dev/null
+++ b/drivers/pwm/sandbox_pwm.c
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <pwm.h>
+#include <asm/test.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+enum {
+	NUM_CHANNELS	= 3,
+};
+
+struct sandbox_pwm_chan {
+	uint period_ns;
+	uint duty_ns;
+	bool enable;
+};
+
+struct sandbox_pwm_priv {
+	struct sandbox_pwm_chan chan[NUM_CHANNELS];
+};
+
+static int sandbox_pwm_set_config(struct udevice *dev, uint channel,
+				  uint period_ns, uint duty_ns)
+{
+	struct sandbox_pwm_priv *priv = dev_get_priv(dev);
+	struct sandbox_pwm_chan *chan;
+
+	if (channel >= NUM_CHANNELS)
+		return -ENOSPC;
+	chan = &priv->chan[channel];
+	chan->period_ns = period_ns;
+	chan->duty_ns = duty_ns;
+
+	return 0;
+}
+
+static int sandbox_pwm_set_enable(struct udevice *dev, uint channel,
+				  bool enable)
+{
+	struct sandbox_pwm_priv *priv = dev_get_priv(dev);
+	struct sandbox_pwm_chan *chan;
+
+	if (channel >= NUM_CHANNELS)
+		return -ENOSPC;
+	chan = &priv->chan[channel];
+	chan->enable = enable;
+
+	return 0;
+}
+
+static const struct pwm_ops sandbox_pwm_ops = {
+	.set_config	= sandbox_pwm_set_config,
+	.set_enable	= sandbox_pwm_set_enable,
+};
+
+static const struct udevice_id sandbox_pwm_ids[] = {
+	{ .compatible = "sandbox,pwm" },
+	{ }
+};
+
+U_BOOT_DRIVER(warm_pwm_sandbox) = {
+	.name		= "pwm_sandbox",
+	.id		= UCLASS_PWM,
+	.of_match	= sandbox_pwm_ids,
+	.ops		= &sandbox_pwm_ops,
+	.priv_auto_alloc_size	= sizeof(struct sandbox_pwm_priv),
+};