[v2,2/2] regulator: add QCOM RPMh regulator driver

Commit Message

David Collins April 25, 2018, 9:04 p.m. UTC

>>> I think that's probably only OK if we have a specific error code for the
>>> regulator being limited in this way otherwise our error handling for I/O
>>> problems involves us trying to reconfigure supplies which seems like it
>>> would be risky.  

>> Would you be ok with -EAGAIN being used for this purpose?

> Using -EAGAIN for "I can't ever read the configuration from this
> regulator" doesn't seem right - it's not like any number of retries
> will ever manage to read the value back.

In this case, the _regulator_get_voltage() call can succeed, but only
after a voltage is explicitly requested from the framework side.  The
intention here would then be to call _regulator_do_set_voltage() with the
constraint min_uV to max_uV range.  After that, subsequent
_regulator_get_voltage() calls will be successful.

Here is the general idea:

 				 "failed to get the current voltage(%d)\n",

Do you still have reservations about using -EAGAIN for this purpose?  If
so, which error code would you suggest using?

Thanks,
David

Comments

Mark Brown May 1, 2018, 9:02 p.m. UTC | #1

On Wed, Apr 25, 2018 at 02:04:56PM -0700, David Collins wrote:

> > Using -EAGAIN for "I can't ever read the configuration from this
> > regulator" doesn't seem right - it's not like any number of retries
> > will ever manage to read the value back.

> In this case, the _regulator_get_voltage() call can succeed, but only
> after a voltage is explicitly requested from the framework side.  The

...

> Do you still have reservations about using -EAGAIN for this purpose?  If
> so, which error code would you suggest using?

Yes, that's clearly a problem - -EAGAIN is more for situations where you
can just immediately retry like signal interruptions.  If the caller
repetedly sits and tries to read the voltage it'll never succeed unless
something else comes along and sets something.

Patch

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 65f9b7c..e61983d 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -910,6 +910,19 @@  static int machine_constraints_voltage(struct
regulator_dev *rdev,
 	    rdev->constraints->min_uV && rdev->constraints->max_uV) {
 		int target_min, target_max;
 		int current_uV = _regulator_get_voltage(rdev);
+		if (current_uV == -EAGAIN) {
+			/*
+			 * Regulator voltage cannot be read until after
+			 * configuration; try setting constraint range.
+			 */
+			rdev_info(rdev, "Setting %d-%duV\n",
+				  rdev->constraints->min_uV,
+				  rdev->constraints->max_uV);
+			_regulator_do_set_voltage(rdev,
+						  rdev->constraints->min_uV,
+						  rdev->constraints->max_uV);
+			current_uV = _regulator_get_voltage(rdev);
+		}
 		if (current_uV < 0) {
 			rdev_err(rdev,