[PATCH V4] ARM: i.MX5: Allow DT clock providers

[mfuzzey@parkeon.com (Martin Fuzzey)]

Currently clock providers defined in the DT are not registered
on i.MX5 platforms since of_clk_init() is not called.

This is not a problem for the SOC's own clocks, which are registered
in code,  but prevents the DT being used to define clocks for external
hardware.

Fix this by calling of_clk_init() and actually using the DT to obtain
the 4 SOC fixed clocks.
These are already defined in the DT but were previously just used to
manually obtain the rate.

Fall back to the old scheme for non DT platforms.

Since the same method may be useful for other i.MX platforms
implement the imx_obtain_fixed_clock() function in common code.

Actually changing other i.MX platforms to use this should be done
later by someone with access to the appropriate hardware.

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>

---
Changelog:
V2: Applied comments from Sascha Hauer:
	* Use kasprintf instead of scnprintf to avoid length limit
	* Avoid use of IS_ERR_OR_NULL

V3: Applied comments from Shawn Guo:
	* Find clocks by path rather than compatible string
	* Remove unnecessary #ifdef CONFIG_OF

V4:
	* Moved clock obtention function to mach-imx/clk.c to allow use by
		other imx platforms (request from Sascha)
	* Added Tested-by from Fabio Estevam
---
 arch/arm/mach-imx/clk-imx51-imx53.c |   44 ++++++-----------------------------
 arch/arm/mach-imx/clk.c             |   37 +++++++++++++++++++++++++++++
 arch/arm/mach-imx/clk.h             |    3 ++
 3 files changed, 48 insertions(+), 36 deletions(-)

diff --git a/arch/arm/mach-imx/clk-imx51-imx53.c b/arch/arm/mach-imx/clk-imx51-imx53.c
index 3228b4e..debd76d 100644
--- a/arch/arm/mach-imx/clk-imx51-imx53.c
+++ b/arch/arm/mach-imx/clk-imx51-imx53.c
@@ -123,11 +123,13 @@ static void __init mx5_clocks_common_init(unsigned long rate_ckil,
 {
 	int i;
 
+	of_clk_init(NULL);
+
 	clk[dummy] = imx_clk_fixed("dummy", 0);
-	clk[ckil] = imx_clk_fixed("ckil", rate_ckil);
-	clk[osc] = imx_clk_fixed("osc", rate_osc);
-	clk[ckih1] = imx_clk_fixed("ckih1", rate_ckih1);
-	clk[ckih2] = imx_clk_fixed("ckih2", rate_ckih2);
+	clk[ckil] = imx_obtain_fixed_clock("ckil", rate_ckil);
+	clk[osc] = imx_obtain_fixed_clock("osc", rate_osc);
+	clk[ckih1] = imx_obtain_fixed_clock("ckih1", rate_ckih1);
+	clk[ckih2] = imx_obtain_fixed_clock("ckih2", rate_ckih2);
 
 	clk[lp_apm] = imx_clk_mux("lp_apm", MXC_CCM_CCSR, 9, 1,
 				lp_apm_sel, ARRAY_SIZE(lp_apm_sel));
@@ -539,42 +541,12 @@ int __init mx53_clocks_init(unsigned long rate_ckil, unsigned long rate_osc,
 	return of_clk_configure();
 }
 
-#ifdef CONFIG_OF
-static void __init clk_get_freq_dt(unsigned long *ckil, unsigned long *osc,
-				   unsigned long *ckih1, unsigned long *ckih2)
-{
-	struct device_node *np;
-
-	/* retrieve the freqency of fixed clocks from device tree */
-	for_each_compatible_node(np, NULL, "fixed-clock") {
-		u32 rate;
-		if (of_property_read_u32(np, "clock-frequency", &rate))
-			continue;
-
-		if (of_device_is_compatible(np, "fsl,imx-ckil"))
-			*ckil = rate;
-		else if (of_device_is_compatible(np, "fsl,imx-osc"))
-			*osc = rate;
-		else if (of_device_is_compatible(np, "fsl,imx-ckih1"))
-			*ckih1 = rate;
-		else if (of_device_is_compatible(np, "fsl,imx-ckih2"))
-			*ckih2 = rate;
-	}
-}
-
 int __init mx51_clocks_init_dt(void)
 {
-	unsigned long ckil, osc, ckih1, ckih2;
-
-	clk_get_freq_dt(&ckil, &osc, &ckih1, &ckih2);
-	return mx51_clocks_init(ckil, osc, ckih1, ckih2);
+	return mx51_clocks_init(0, 0, 0, 0);
 }
 
 int __init mx53_clocks_init_dt(void)
 {
-	unsigned long ckil, osc, ckih1, ckih2;
-
-	clk_get_freq_dt(&ckil, &osc, &ckih1, &ckih2);
-	return mx53_clocks_init(ckil, osc, ckih1, ckih2);
+	return mx53_clocks_init(0, 0, 0, 0);
 }
-#endif
diff --git a/arch/arm/mach-imx/clk.c b/arch/arm/mach-imx/clk.c
index f5e8be8..f2c73f2 100644
--- a/arch/arm/mach-imx/clk.c
+++ b/arch/arm/mach-imx/clk.c
@@ -1,3 +1,40 @@
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/slab.h>
 #include <linux/spinlock.h>
 
+#include "clk.h"
+
 DEFINE_SPINLOCK(imx_ccm_lock);
+
+static struct clk * __init imx_obtain_fixed_clock_from_dt(const char *name)
+{
+	struct of_phandle_args phandle = {0};
+	struct clk *clk = ERR_PTR(-ENODEV);
+	char *path;
+
+	path = kasprintf(GFP_KERNEL, "/clocks/%s", name);
+	if (!path)
+		return ERR_PTR(-ENOMEM);
+
+	phandle.np = of_find_node_by_path(path);
+	kfree(path);
+
+	if (phandle.np) {
+		clk = of_clk_get_from_provider(&phandle);
+		of_node_put(phandle.np);
+	}
+	return clk;
+}
+
+struct clk * __init imx_obtain_fixed_clock(
+			const char *name, unsigned long rate)
+{
+	struct clk *clk;
+
+	clk = imx_obtain_fixed_clock_from_dt(name);
+	if (IS_ERR(clk))
+		clk = imx_clk_fixed(name, rate);
+	return clk;
+}
diff --git a/arch/arm/mach-imx/clk.h b/arch/arm/mach-imx/clk.h
index d9d9d9c..780fd67 100644
--- a/arch/arm/mach-imx/clk.h
+++ b/arch/arm/mach-imx/clk.h
@@ -29,6 +29,9 @@ struct clk *clk_register_gate2(struct device *dev, const char *name,
 		void __iomem *reg, u8 bit_idx,
 		u8 clk_gate_flags, spinlock_t *lock);
 
+struct clk * __init imx_obtain_fixed_clock(
+			const char *name, unsigned long rate);
+
 static inline struct clk *imx_clk_gate2(const char *name, const char *parent,
 		void __iomem *reg, u8 shift)
 {