[PATCH] CLK: ARC: Set initial pll output frequency specified in device tree

[Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>]

Add option to set initial output frequency of plls via
"clock-frequency" property in pll's device tree node.
This frequency will be set while pll driver probed.

The usage example is setting CPU clock frequency on boot
See discussion:
https://www.mail-archive.com/linux-snps-arc@lists.infradead.org/msg02689.html

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
 .../bindings/clock/snps,hsdk-pll-clock.txt         |  5 ++++
 .../devicetree/bindings/clock/snps,pll-clock.txt   |  5 ++++
 drivers/clk/axs10x/pll_clock.c                     | 34 ++++++++++++++++++++--
 drivers/clk/clk-hsdk-pll.c                         | 34 ++++++++++++++++++++--
 4 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt b/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt
index c56c755..5703059 100644
--- a/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt
+++ b/Documentation/devicetree/bindings/clock/snps,hsdk-pll-clock.txt
@@ -13,6 +13,10 @@ Required properties:
 - clocks: shall be the input parent clock phandle for the PLL.
 - #clock-cells: from common clock binding; Should always be set to 0.
 
+Optional properties:
+- clock-frequency: output frequency generated by pll in Hz which will be set
+while probing. Should be a single cell.
+
 Example:
 	input_clk: input-clk {
 		clock-frequency = <33333333>;
@@ -25,4 +29,5 @@ Example:
 		reg = <0x00 0x10>;
 		#clock-cells = <0>;
 		clocks = <&input_clk>;
+		clock-frequency = <1000000000>;
 	};
diff --git a/Documentation/devicetree/bindings/clock/snps,pll-clock.txt b/Documentation/devicetree/bindings/clock/snps,pll-clock.txt
index 11fe487..5908f99 100644
--- a/Documentation/devicetree/bindings/clock/snps,pll-clock.txt
+++ b/Documentation/devicetree/bindings/clock/snps,pll-clock.txt
@@ -13,6 +13,10 @@ registers and second for corresponding LOCK CGU register.
 - clocks: shall be the input parent clock phandle for the PLL.
 - #clock-cells: from common clock binding; Should always be set to 0.
 
+Optional properties:
+- clock-frequency: output frequency generated by pll in Hz which will be set
+while probing. Should be a single cell.
+
 Example:
 	input-clk: input-clk {
 		clock-frequency = <33333333>;
@@ -25,4 +29,5 @@ Example:
 		reg = <0x80 0x10>, <0x100 0x10>;
 		#clock-cells = <0>;
 		clocks = <&input-clk>;
+		clock-frequency = <100000000>;
 	};
diff --git a/drivers/clk/axs10x/pll_clock.c b/drivers/clk/axs10x/pll_clock.c
index 25d8c24..3f4345d 100644
--- a/drivers/clk/axs10x/pll_clock.c
+++ b/drivers/clk/axs10x/pll_clock.c
@@ -11,6 +11,7 @@
 #include <linux/platform_device.h>
 #include <linux/module.h>
 #include <linux/clk-provider.h>
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/device.h>
@@ -215,6 +216,25 @@ static const struct clk_ops axs10x_pll_ops = {
 	.set_rate = axs10x_pll_set_rate,
 };
 
+static void set_pll_rate_from_of(struct clk *clk, struct device_node *node)
+{
+	u32 requested_rate;
+
+	/* If we specify initial pll output frequency try to set it */
+	if (of_property_read_u32(node, "clock-frequency", &requested_rate))
+		return;
+
+	if (clk_prepare_enable(clk)) {
+		pr_err("Cannot enable %s clock.\n", node->name);
+		return;
+	}
+
+	if (clk_set_rate(clk, requested_rate))
+		pr_err("Cannot set %s clock rate.\n", node->name);
+
+	pr_debug("Set %s clock to %u\n", node->name, requested_rate);
+}
+
 static int axs10x_pll_clk_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -258,8 +278,15 @@ static int axs10x_pll_clk_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	return of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
-			&pll_clk->hw);
+	ret =  of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
+				      &pll_clk->hw);
+	if (ret)
+		return ret;
+
+	/* If we specify initial pll output frequency in dts try to set it */
+	set_pll_rate_from_of(pll_clk->hw.clk, dev->of_node);
+
+	return 0;
 }
 
 static int axs10x_pll_clk_remove(struct platform_device *pdev)
@@ -311,6 +338,9 @@ static void __init of_axs10x_pll_clk_setup(struct device_node *node)
 		goto err_unregister_clk;
 	}
 
+	/* If we specify initial pll output frequency in dts try to set it */
+	set_pll_rate_from_of(pll_clk->hw.clk, node);
+
 	return;
 
 err_unregister_clk:
diff --git a/drivers/clk/clk-hsdk-pll.c b/drivers/clk/clk-hsdk-pll.c
index bbf23717..74fd006 100644
--- a/drivers/clk/clk-hsdk-pll.c
+++ b/drivers/clk/clk-hsdk-pll.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/clk-provider.h>
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -295,6 +296,25 @@ static const struct clk_ops hsdk_pll_ops = {
 	.set_rate = hsdk_pll_set_rate,
 };
 
+static void set_pll_rate_from_of(struct clk *clk, struct device_node *node)
+{
+	u32 requested_rate;
+
+	/* If we specify initial pll output frequency try to set it */
+	if (of_property_read_u32(node, "clock-frequency", &requested_rate))
+		return;
+
+	if (clk_prepare_enable(clk)) {
+		pr_err("Cannot enable %s clock.\n", node->name);
+		return;
+	}
+
+	if (clk_set_rate(clk, requested_rate))
+		pr_err("Cannot set %s clock rate.\n", node->name);
+
+	pr_debug("Set %s clock to %u\n", node->name, requested_rate);
+}
+
 static int hsdk_pll_clk_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -340,8 +360,15 @@ static int hsdk_pll_clk_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	return of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
-			&pll_clk->hw);
+	ret =  of_clk_add_hw_provider(dev->of_node, of_clk_hw_simple_get,
+				      &pll_clk->hw);
+	if (ret)
+		return ret;
+
+	/* If we specify initial pll output frequency in dts try to set it */
+	set_pll_rate_from_of(pll_clk->hw.clk, dev->of_node);
+
+	return 0;
 }
 
 static int hsdk_pll_clk_remove(struct platform_device *pdev)
@@ -400,6 +427,9 @@ static void __init of_hsdk_pll_clk_setup(struct device_node *node)
 		goto err_unmap_spec_regs;
 	}
 
+	/* If we specify initial pll output frequency in dts try to set it */
+	set_pll_rate_from_of(pll_clk->hw.clk, node);
+
 	return;
 
 err_unmap_spec_regs:
-- 
2.9.3