[PATCH V3] 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.

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.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
---
 arch/arm/mach-imx/clk-imx51-imx53.c |   76 ++++++++++++++++++-----------------
 1 files changed, 40 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..606c679 100644
--- a/arch/arm/mach-imx/clk-imx51-imx53.c
+++ b/arch/arm/mach-imx/clk-imx51-imx53.c
@@ -117,17 +117,51 @@ enum imx5_clks {
 static struct clk *clk[clk_max];
 static struct clk_onecell_data clk_data;
 
+
+static struct clk * __init mx5_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;
+}
+
+static struct clk * __init mx5_obtain_fixed_clock(
+			const char *name, unsigned long rate)
+{
+	struct clk *clk;
+
+	clk = mx5_obtain_fixed_clock_from_dt(name);
+	if (IS_ERR(clk))
+		clk = imx_clk_fixed(name, rate);
+	return clk;
+}
+
 static void __init mx5_clocks_common_init(unsigned long rate_ckil,
 		unsigned long rate_osc, unsigned long rate_ckih1,
 		unsigned long rate_ckih2)
 {
 	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] = mx5_obtain_fixed_clock("ckil", rate_ckil);
+	clk[osc] = mx5_obtain_fixed_clock("osc", rate_osc);
+	clk[ckih1] = mx5_obtain_fixed_clock("ckih1", rate_ckih1);
+	clk[ckih2] = mx5_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 +573,12 @@ 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