[PATCH] cpufreq: OMAP: instantiate omap-cpufreq as a platform_driver

[Kevin Hilman]

From: Nishanth Menon <nm at ti.com>

As multi-platform build is being adopted by more and more ARM platforms,
initcall function should be used very carefully.  For example, when
CONFIG_ARM_OMAP2PLUS_CPUFREQ is built in the kernel, omap_cpufreq_init()
will be called on all the platforms to initialize omap-cpufreq driver.

Further, on OMAP, we now use Soc generic cpufreq-cpu0 driver using device
tree entries.  To allow cpufreq-cpu0 and omap-cpufreq drivers to co-exist
for OMAP in a single image, we need to ensure the following:
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 device tree nodes, to ensure that omap-cpufreq
and cpufreq-cpu0 don't conflict in managing the frequency of the
same CPU, we should not permit omap-cpufreq to be probed.

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

To eliminate this undesired these effects, we change omap-cpufreq
driver to have it instantiated as a platform_driver and register
"omap-cpufreq" device only when booted without device tree nodes on
OMAP platforms.

This allows the following:
a) Will only run on platforms that create the platform_device
   "omap-cpufreq".
b) Since the platform_device is registered only when device tree nodes
   are *not* populated, omap-cpufreq driver does not conflict with
   the usage of cpufreq-cpu0 driver which is used on OMAP platforms when
   device tree nodes are present.

Inspired by commit 5553f9e26f6f49a93ba732fd222eac6973a4cf35
(cpufreq: instantiate cpufreq-cpu0 as a platform_driver)

Cc: Kevin Hilman <khilman at linaro.org>
Cc: Rajendra Nayak <rnayak at ti.com>
Cc: Paul Walmsley <paul at pwsan.com>
Cc: "Benoît Cousson" <b-cousson at ti.com>
Cc: Jon Hunter <jon-hunter at ti.com>
Cc: Keerthy <j-keerthy at ti.com>
Cc: Santosh Shilimkar <santosh.shilimkar at ti.com>
Cc: Shawn Guo <shawn.guo at linaro.org>
[robherring2 at gmail.com: reported conflict of omap-cpufreq vs other
driver in an non-device tree supported boot]
Reported-by: Rob Herring <robherring2 at gmail.com>
Signed-off-by: Nishanth Menon <nm at ti.com>
Acked-by: Viresh Kumar <viresh.kumar at linaro.org>
Signed-off-by: Kevin Hilman <khilman at linaro.org>
---
Rafael, can you add this one for v3.10?  It applies on top the
rest of your cpufreq changes and I've verified that the OMAP
changes are OK and don't conflict with anything else we have
queued for v3.10 on OMAP.

This patch was previously part of a 2-patch series, but the 
other part is still in discussion, and this part can be merged
independently.

 arch/arm/mach-omap2/pm.c       |  9 +++++++++
 drivers/cpufreq/omap-cpufreq.c | 19 ++++++++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-omap2/pm.c b/arch/arm/mach-omap2/pm.c
index 673a4c1..8d15f9a 100644
--- a/arch/arm/mach-omap2/pm.c
+++ b/arch/arm/mach-omap2/pm.c
@@ -265,6 +265,12 @@ static void __init omap4_init_voltages(void)
 	omap2_set_init_voltage("iva", "dpll_iva_m5x2_ck", "iva");
 }
 
+static inline void omap_init_cpufreq(void)
+{
+	struct platform_device_info devinfo = { .name = "omap-cpufreq", };
+	platform_device_register_full(&devinfo);
+}
+
 static int __init omap2_common_pm_init(void)
 {
 	if (!of_have_populated_dt())
@@ -294,6 +300,9 @@ int __init omap2_common_pm_late_init(void)
 
 		/* Smartreflex device init */
 		omap_devinit_smartreflex();
+
+		/* cpufreq dummy device instantiation */
+		omap_init_cpufreq();
 	}
 
 #ifdef CONFIG_SUSPEND
diff --git a/drivers/cpufreq/omap-cpufreq.c b/drivers/cpufreq/omap-cpufreq.c
index 9128c07..d4f84b8 100644
--- a/drivers/cpufreq/omap-cpufreq.c
+++ b/drivers/cpufreq/omap-cpufreq.c
@@ -25,6 +25,7 @@
 #include <linux/opp.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
+#include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 
 #include <asm/smp_plat.h>
@@ -252,7 +253,7 @@ static struct cpufreq_driver omap_driver = {
 	.attr		= omap_cpufreq_attr,
 };
 
-static int __init omap_cpufreq_init(void)
+static int omap_cpufreq_probe(struct platform_device *pdev)
 {
 	mpu_dev = get_cpu_device(0);
 	if (!mpu_dev) {
@@ -280,12 +281,20 @@ static int __init omap_cpufreq_init(void)
 	return cpufreq_register_driver(&omap_driver);
 }
 
-static void __exit omap_cpufreq_exit(void)
+static int omap_cpufreq_remove(struct platform_device *pdev)
 {
-	cpufreq_unregister_driver(&omap_driver);
+	return cpufreq_unregister_driver(&omap_driver);
 }
 
+static struct platform_driver omap_cpufreq_platdrv = {
+	.driver = {
+		.name	= "omap-cpufreq",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= omap_cpufreq_probe,
+	.remove		= omap_cpufreq_remove,
+};
+module_platform_driver(omap_cpufreq_platdrv);
+
 MODULE_DESCRIPTION("cpufreq driver for OMAP SoCs");
 MODULE_LICENSE("GPL");
-module_init(omap_cpufreq_init);
-module_exit(omap_cpufreq_exit);
-- 
1.8.2