clk: add clk_round_rate()

It returns the rate which will be set if you ask clk_set_rate() to set
that rate. It provides a way to query exactly what rate you'll get if
you call clk_set_rate() with that same argument.
So essentially, clk_round_rate() and clk_set_rate() are equivalent
except the former does not modify the clock hardware in any way.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Sean Anderson <seanga2@gmail.com>

arch/sandbox/include/asm/clk.h

@@ -105,6 +105,15 @@ int sandbox_clk_test_get_bulk(struct udevice *dev);
  * @return:	The rate of the clock.
  */
 ulong sandbox_clk_test_get_rate(struct udevice *dev, int id);
+/**
+ * sandbox_clk_test_round_rate - Ask the sandbox clock test device to round a
+ * clock's rate.
+ *
+ * @dev:	The sandbox clock test (client) device.
+ * @id:		The test device's clock ID to configure.
+ * @return:	The rounded rate of the clock.
+ */
+ulong sandbox_clk_test_round_rate(struct udevice *dev, int id, ulong rate);
 /**
  * sandbox_clk_test_set_rate - Ask the sandbox clock test device to set a
  * clock's rate.

drivers/clk/clk-uclass.c

@@ -523,6 +523,21 @@ long long clk_get_parent_rate(struct clk *clk)
 	return pclk->rate;
 }
 
+ulong clk_round_rate(struct clk *clk, ulong rate)
+{
+	const struct clk_ops *ops;
+
+	debug("%s(clk=%p, rate=%lu)\n", __func__, clk, rate);
+	if (!clk_valid(clk))
+		return 0;
+
+	ops = clk_dev_ops(clk->dev);
+	if (!ops->round_rate)
+		return -ENOSYS;
+
+	return ops->round_rate(clk, rate);
+}
+
 ulong clk_set_rate(struct clk *clk, ulong rate)
 {
 	const struct clk_ops *ops;

drivers/clk/clk_sandbox.c

@@ -30,6 +30,22 @@ static ulong sandbox_clk_get_rate(struct clk *clk)
 	return priv->rate[clk->id];
 }
 
+static ulong sandbox_clk_round_rate(struct clk *clk, ulong rate)
+{
+	struct sandbox_clk_priv *priv = dev_get_priv(clk->dev);
+
+	if (!priv->probed)
+		return -ENODEV;
+
+	if (clk->id >= SANDBOX_CLK_ID_COUNT)
+		return -EINVAL;
+
+	if (!rate)
+		return -EINVAL;
+
+	return rate;
+}
+
 static ulong sandbox_clk_set_rate(struct clk *clk, ulong rate)
 {
 	struct sandbox_clk_priv *priv = dev_get_priv(clk->dev);
@@ -103,6 +119,7 @@ static int sandbox_clk_free(struct clk *clk)
 }
 
 static struct clk_ops sandbox_clk_ops = {
+	.round_rate	= sandbox_clk_round_rate,
 	.get_rate	= sandbox_clk_get_rate,
 	.set_rate	= sandbox_clk_set_rate,
 	.enable		= sandbox_clk_enable,

drivers/clk/clk_sandbox_test.c

@@ -86,6 +86,16 @@ ulong sandbox_clk_test_get_rate(struct udevice *dev, int id)
 	return clk_get_rate(sbct->clkps[id]);
 }
 
+ulong sandbox_clk_test_round_rate(struct udevice *dev, int id, ulong rate)
+{
+	struct sandbox_clk_test *sbct = dev_get_priv(dev);
+
+	if (id < 0 || id >= SANDBOX_CLK_TEST_ID_COUNT)
+		return -EINVAL;
+
+	return clk_round_rate(sbct->clkps[id], rate);
+}
+
 ulong sandbox_clk_test_set_rate(struct udevice *dev, int id, ulong rate)
 {
 	struct sandbox_clk_test *sbct = dev_get_priv(dev);

include/clk-uclass.h

@@ -61,6 +61,14 @@ struct clk_ops {
 	 * @return 0 if OK, or a negative error code.
 	 */
 	int (*rfree)(struct clk *clock);
+	/**
+	 * round_rate() - Adjust a rate to the exact rate a clock can provide.
+	 *
+	 * @clk:	The clock to manipulate.
+	 * @rate:	Desidered clock rate in Hz.
+	 * @return rounded rate in Hz, or -ve error code.
+	 */
+	ulong (*round_rate)(struct clk *clk, ulong rate);
 	/**
 	 * get_rate() - Get current clock rate.
 	 *

include/clk.h

@@ -366,6 +366,29 @@ struct clk *clk_get_parent(struct clk *clk);
  */
 long long clk_get_parent_rate(struct clk *clk);
 
+/**
+ * clk_round_rate() - Adjust a rate to the exact rate a clock can provide
+ *
+ * This answers the question "if I were to pass @rate to clk_set_rate(),
+ * what clock rate would I end up with?" without changing the hardware
+ * in any way.  In other words:
+ *
+ *   rate = clk_round_rate(clk, r);
+ *
+ * and:
+ *
+ *   rate = clk_set_rate(clk, r);
+ *
+ * are equivalent except the former does not modify the clock hardware
+ * in any way.
+ *
+ * @clk: A clock struct that was previously successfully requested by
+ *       clk_request/get_by_*().
+ * @rate: desired clock rate in Hz.
+ * @return rounded rate in Hz, or -ve error code.
+ */
+ulong clk_round_rate(struct clk *clk, ulong rate);
+
 /**
  * clk_set_rate() - Set current clock rate.
  *
@@ -482,6 +505,11 @@ static inline long long clk_get_parent_rate(struct clk *clk)
 	return -ENOSYS;
 }
 
+static inline ulong clk_round_rate(struct clk *clk, ulong rate)
+{
+	return -ENOSYS;
+}
+
 static inline ulong clk_set_rate(struct clk *clk, ulong rate)
 {
 	return -ENOSYS;

test/dm/clk.c

@@ -112,6 +112,28 @@ static int dm_test_clk(struct unit_test_state *uts)
 	rate = sandbox_clk_test_set_rate(dev_test, SANDBOX_CLK_TEST_ID_I2C, 0);
 	ut_assert(IS_ERR_VALUE(rate));
 
+	ut_asserteq(10000, sandbox_clk_test_get_rate(dev_test,
+						     SANDBOX_CLK_TEST_ID_SPI));
+	ut_asserteq(20000, sandbox_clk_test_get_rate(dev_test,
+						     SANDBOX_CLK_TEST_ID_I2C));
+
+	ut_asserteq(5000, sandbox_clk_test_round_rate(dev_test,
+						      SANDBOX_CLK_TEST_ID_SPI,
+						      5000));
+	ut_asserteq(7000, sandbox_clk_test_round_rate(dev_test,
+						      SANDBOX_CLK_TEST_ID_I2C,
+						      7000));
+
+	ut_asserteq(10000, sandbox_clk_test_get_rate(dev_test,
+						     SANDBOX_CLK_TEST_ID_SPI));
+	ut_asserteq(20000, sandbox_clk_test_get_rate(dev_test,
+						     SANDBOX_CLK_TEST_ID_I2C));
+
+	rate = sandbox_clk_test_round_rate(dev_test, SANDBOX_CLK_TEST_ID_SPI, 0);
+	ut_assert(IS_ERR_VALUE(rate));
+	rate = sandbox_clk_test_round_rate(dev_test, SANDBOX_CLK_TEST_ID_I2C, 0);
+	ut_assert(IS_ERR_VALUE(rate));
+
 	ut_asserteq(10000, sandbox_clk_test_get_rate(dev_test,
 						     SANDBOX_CLK_TEST_ID_SPI));
 	ut_asserteq(20000, sandbox_clk_test_get_rate(dev_test,