ARM: OMAP2+: Powerdomain: Remove the need to always have a voltdm associated to a pwrdm

The powerdomain framework currently expects all powerdomains to be associated with
a corresponding voltagedomain. For some SoCs' (like the already existing AM33xx
family, or for the upcoming AM437x and DRA7 SoCs') which
do not have a Voltage controller/Voltage Processor (neither the SR I2C
bus to communicate with the PMIC) there is no need for a Powerdomain to have
a voltage domain association since there is no auto-scaling of voltages possible
using the voltage FSM.

Extend the arch operations to add an api which the powerdomain core can
then use to identify if a voltdm lookup and association for a powerdomain
is really needed.

Acked-by: Nishanth Menon <nm@ti.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Afzal Mohammed <afzal@ti.com> # am335x evm
Signed-off-by: Kevin Hilman <khilman@linaro.org>

arch/arm/mach-omap2/powerdomain.c

@@ -102,6 +102,10 @@ static int _pwrdm_register(struct powerdomain *pwrdm)
 	if (_pwrdm_lookup(pwrdm->name))
 		return -EEXIST;
 
+	if (arch_pwrdm && arch_pwrdm->pwrdm_has_voltdm)
+		if (!arch_pwrdm->pwrdm_has_voltdm())
+			goto skip_voltdm;
+
 	voltdm = voltdm_lookup(pwrdm->voltdm.name);
 	if (!voltdm) {
 		pr_err("powerdomain: %s: voltagedomain %s does not exist\n",
@@ -111,6 +115,7 @@ static int _pwrdm_register(struct powerdomain *pwrdm)
 	pwrdm->voltdm.ptr = voltdm;
 	INIT_LIST_HEAD(&pwrdm->voltdm_node);
 	voltdm_add_pwrdm(voltdm, pwrdm);
+skip_voltdm:
 	spin_lock_init(&pwrdm->_lock);
 
 	list_add(&pwrdm->node, &pwrdm_list);

arch/arm/mach-omap2/powerdomain.h

@@ -166,6 +166,7 @@ struct powerdomain {
  * @pwrdm_disable_hdwr_sar: Disable Hardware Save-Restore feature for a pd
  * @pwrdm_set_lowpwrstchange: Enable pd transitions from a shallow to deep sleep
  * @pwrdm_wait_transition: Wait for a pd state transition to complete
+ * @pwrdm_has_voltdm: Check if a voltdm association is needed
  *
  * Regarding @pwrdm_set_lowpwrstchange: On the OMAP2 and 3-family
  * chips, a powerdomain's power state is not allowed to directly
@@ -196,6 +197,7 @@ struct pwrdm_ops {
 	int	(*pwrdm_disable_hdwr_sar)(struct powerdomain *pwrdm);
 	int	(*pwrdm_set_lowpwrstchange)(struct powerdomain *pwrdm);
 	int	(*pwrdm_wait_transition)(struct powerdomain *pwrdm);
+	int	(*pwrdm_has_voltdm)(void);
 };
 
 int pwrdm_register_platform_funcs(struct pwrdm_ops *custom_funcs);