Enforce limits in regulator framework

[Mark Kettenis]

The regulators defined in the FDT typically have limits associated
with them.  The diff below enforces those limits.

Enforcing the limits also happens when the regulator is registered.
As a consequence regulators will be properly initialized even when the
firmware (i.e. U-Boot) doesn't do that.

ok?


Index: dev/ofw/ofw_regulator.c
===================================================================
RCS file: /cvs/src/sys/dev/ofw/ofw_regulator.c,v
retrieving revision 1.2
diff -u -p -r1.2 ofw_regulator.c
--- dev/ofw/ofw_regulator.c     18 Nov 2017 13:48:50 -0000      1.2
+++ dev/ofw/ofw_regulator.c     16 Dec 2017 16:37:46 -0000
@@ -30,6 +30,18 @@ LIST_HEAD(, regulator_device) regulator_
 void
 regulator_register(struct regulator_device *rd)
 {
+       rd->rd_min = OF_getpropint(rd->rd_node, "regulator-min-microvolt", 0);
+       rd->rd_max = OF_getpropint(rd->rd_node, "regulator-max-microvolt", ~0);
+       KASSERT(rd->rd_min <= rd->rd_max);
+
+       if (rd->rd_get_voltage && rd->rd_set_voltage) {
+               uint32_t voltage = rd->rd_get_voltage(rd->rd_cookie);
+               if (voltage < rd->rd_min)
+                       rd->rd_set_voltage(rd->rd_cookie, rd->rd_min);
+               if (voltage > rd->rd_max)
+                       rd->rd_set_voltage(rd->rd_cookie, rd->rd_max);
+       }
+
        rd->rd_phandle = OF_getpropint(rd->rd_node, "phandle", 0);
        if (rd->rd_phandle == 0)
                return;
@@ -127,8 +139,12 @@ regulator_set_voltage(uint32_t phandle, 
                        break;
        }
 
+       /* Check limits. */
+       if (rd && (voltage < rd->rd_min || voltage > rd->rd_max))
+               return EINVAL;
+
        if (rd && rd->rd_set_voltage)
                return rd->rd_set_voltage(rd->rd_cookie, voltage);
 
-       return -1;
+       return ENODEV;
 }
Index: dev/ofw/ofw_regulator.h
===================================================================
RCS file: /cvs/src/sys/dev/ofw/ofw_regulator.h,v
retrieving revision 1.3
diff -u -p -r1.3 ofw_regulator.h
--- dev/ofw/ofw_regulator.h     18 Nov 2017 21:03:23 -0000      1.3
+++ dev/ofw/ofw_regulator.h     16 Dec 2017 16:37:46 -0000
@@ -24,6 +24,8 @@ struct regulator_device {
        uint32_t (*rd_get_voltage)(void *);
        int     (*rd_set_voltage)(void *, uint32_t);
 
+       uint32_t rd_min, rd_max;
+
        LIST_ENTRY(regulator_device) rd_list;
        uint32_t rd_phandle;
 };