The get_optimum_mode() for regulator drivers is passed the input
voltage and output voltage as well as the current. This is because, in
theory, the optimum mode can depend on all three things.
It turns out that for all regulator drivers in mainline only the
current is looked at when implementing get_optimum_mode(). None of the
drivers take the input or output voltage into account. Despite the
fact that none of the drivers take the input or output voltage into
account, though, the regulator framework will error out before calling
into get_optimum_mode() if it doesn't know the input or output
voltage.
The above behavior turned out to be a probelm for some boards when we
landed commit efb0cb50c427 ("regulator: qcom-rpmh: Implement
get_optimum_mode(), not set_load()"). Before that change we'd have no
problems running drms_uA_update() for RPMH regulators even if a
regulator's input or output voltage was unknown. After that change
drms_uA_update() started to fail. This is because typically boards
using RPMH regulators don't model the input supplies of RPMH
regulators. Input supplies for RPMH regulators nearly always come from
the output of other RPMH regulators (or always-on regulators) and RPMH
firmware is initialized with this knowledge and handles enabling (and
adjusting the voltage of) input supplies. While we could model the
parent/child relationship of the regulators in Linux, many boards
don't bother since it adds extra overhead.
Let's change the regulator core to make things work again. Now if we
fail to get the input or output voltage we'll still call into
get_optimum_mode() and we'll just pass error codes in for input_uV
and/or output_uV parameters.
Since no existing regulator drivers even look at input_uV and
output_uV we don't need to add this error handling anywhere right
now. We'll add some comments in the core so that it's obvious that (if
regulator drivers care) it's up to them to add the checks.
Reported-by: Andrew Halaney <[email protected]>
Fixes: efb0cb50c427 ("regulator: qcom-rpmh: Implement get_optimum_mode(), not set_load()")
Signed-off-by: Douglas Anderson <[email protected]>
---
(no changes since v1)
drivers/regulator/core.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 5b5da14976c2..0bc4b9b0a885 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -979,10 +979,13 @@ static int drms_uA_update(struct regulator_dev *rdev)
} else {
/* get output voltage */
output_uV = regulator_get_voltage_rdev(rdev);
- if (output_uV <= 0) {
- rdev_err(rdev, "invalid output voltage found\n");
- return -EINVAL;
- }
+
+ /*
+ * Don't return an error; if regulator driver cares about
+ * output_uV then it's up to the driver to validate.
+ */
+ if (output_uV <= 0)
+ rdev_dbg(rdev, "invalid output voltage found\n");
/* get input voltage */
input_uV = 0;
@@ -990,10 +993,13 @@ static int drms_uA_update(struct regulator_dev *rdev)
input_uV = regulator_get_voltage(rdev->supply);
if (input_uV <= 0)
input_uV = rdev->constraints->input_uV;
- if (input_uV <= 0) {
- rdev_err(rdev, "invalid input voltage found\n");
- return -EINVAL;
- }
+
+ /*
+ * Don't return an error; if regulator driver cares about
+ * input_uV then it's up to the driver to validate.
+ */
+ if (input_uV <= 0)
+ rdev_dbg(rdev, "invalid input voltage found\n");
/* now get the optimum mode for our new total regulator load */
mode = rdev->desc->ops->get_optimum_mode(rdev, input_uV,
--
2.37.2.672.g94769d06f0-goog
On Wed, Aug 24, 2022 at 02:22:56PM -0700, Douglas Anderson wrote:
> The get_optimum_mode() for regulator drivers is passed the input
> voltage and output voltage as well as the current. This is because, in
> theory, the optimum mode can depend on all three things.
>
> It turns out that for all regulator drivers in mainline only the
> current is looked at when implementing get_optimum_mode(). None of the
> drivers take the input or output voltage into account. Despite the
> fact that none of the drivers take the input or output voltage into
> account, though, the regulator framework will error out before calling
> into get_optimum_mode() if it doesn't know the input or output
> voltage.
>
> The above behavior turned out to be a probelm for some boards when we
> landed commit efb0cb50c427 ("regulator: qcom-rpmh: Implement
> get_optimum_mode(), not set_load()"). Before that change we'd have no
> problems running drms_uA_update() for RPMH regulators even if a
> regulator's input or output voltage was unknown. After that change
> drms_uA_update() started to fail. This is because typically boards
> using RPMH regulators don't model the input supplies of RPMH
> regulators. Input supplies for RPMH regulators nearly always come from
> the output of other RPMH regulators (or always-on regulators) and RPMH
> firmware is initialized with this knowledge and handles enabling (and
> adjusting the voltage of) input supplies. While we could model the
> parent/child relationship of the regulators in Linux, many boards
> don't bother since it adds extra overhead.
>
> Let's change the regulator core to make things work again. Now if we
> fail to get the input or output voltage we'll still call into
> get_optimum_mode() and we'll just pass error codes in for input_uV
> and/or output_uV parameters.
>
> Since no existing regulator drivers even look at input_uV and
> output_uV we don't need to add this error handling anywhere right
> now. We'll add some comments in the core so that it's obvious that (if
> regulator drivers care) it's up to them to add the checks.
>
> Reported-by: Andrew Halaney <[email protected]>
> Fixes: efb0cb50c427 ("regulator: qcom-rpmh: Implement get_optimum_mode(), not set_load()")
> Signed-off-by: Douglas Anderson <[email protected]>
Tested-by: Andrew Halaney <[email protected]>
Thanks again for the quick patches!
- Andrew
On Wed, 24 Aug 2022 14:22:56 -0700, Douglas Anderson wrote:
> The get_optimum_mode() for regulator drivers is passed the input
> voltage and output voltage as well as the current. This is because, in
> theory, the optimum mode can depend on all three things.
>
> It turns out that for all regulator drivers in mainline only the
> current is looked at when implementing get_optimum_mode(). None of the
> drivers take the input or output voltage into account. Despite the
> fact that none of the drivers take the input or output voltage into
> account, though, the regulator framework will error out before calling
> into get_optimum_mode() if it doesn't know the input or output
> voltage.
>
> [...]
Applied to
broonie/regulator.git for-next
Thanks!
[1/2] regulator: core: Require regulator drivers to check uV for get_optimum_mode()
commit: 55841199050d0c6c44eb7f24717816e6e372599f
[2/2] regulator: core: Don't err if allow-set-load but no allowed-modes
commit: 57919f4a2ea47f75ac6117f7d99831f7fbd89bc7
All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.
You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.
If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.
Please add any relevant lists and maintainers to the CCs when replying
to this mail.
Thanks,
Mark