[PATCH V2 8/8] cpufreq: OMAP: donot allow to be used with device tree

[Nishanth Menon <nm@ti.com>]

We now use Soc generic cpufreq-cpu0 driver using DT entries.
However to allow cpufreq-cpu0 and omap-cpufreq drivers to co-exist,
we need to ensure the following using the same image:
1. With device tree boot, we use cpufreq-cpu0
2. With non device tree boot, we use omap-cpufreq

In the case of (1), we will have cpu OPPs and regulator registered
as part of the DT, to ensure that omap-cpufreq and cpufreq-cpu0 don't
conflict in managing the frequency of the same cpu, we should not
permit init to pass in omap-cpufreq.

In the case of (2), we will not have the cpufreq-cpu0 device, hence
only omap-cpufreq will be active.

So, to acommodate both these usage conditions, we fail init of
omap-cpufreq when we boot with device tree.

Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Jon Hunter <jon-hunter@ti.com>
Cc: "Benoît Cousson" <b-cousson@ti.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Keerthy <j-keerthy@ti.com>
Cc: linux-omap@vger.kernel.org
Cc: devicetree-discuss@lists.ozlabs.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: cpufreq@vger.kernel.org
Cc: linux-pm@vger.kernel.org

Signed-off-by: Nishanth Menon <nm@ti.com>
---
Changes in V2:
	- donot remove support for omap-cpufreq in non-DT boot
	- little more verbose commit log
V1: https://patchwork.kernel.org/patch/2273641/

 drivers/cpufreq/omap-cpufreq.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/cpufreq/omap-cpufreq.c b/drivers/cpufreq/omap-cpufreq.c
index 9128c07..9382ed0 100644
--- a/drivers/cpufreq/omap-cpufreq.c
+++ b/drivers/cpufreq/omap-cpufreq.c
@@ -22,6 +22,7 @@
 #include <linux/err.h>
 #include <linux/clk.h>
 #include <linux/io.h>
+#include <linux/of.h>
 #include <linux/opp.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
@@ -174,6 +175,19 @@ static inline void freq_table_free(void)
 static int __cpuinit omap_cpu_init(struct cpufreq_policy *policy)
 {
 	int result = 0;
+	struct device_node *np;
+
+	/*
+	 * If we have a device tree node describing OPPs,
+	 * we will NOT permit usage of omap-cpufreq driver.
+	 * use cpufreq-cpu0 driver to manage.
+	 */
+	if (of_have_populated_dt()) {
+		for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
+			if (of_get_property(np, "operating-points", NULL))
+				return -EPERM;
+		}
+	}
 
 	mpu_clk = clk_get(NULL, "cpufreq_ck");
 	if (IS_ERR(mpu_clk))
-- 
1.7.9.5