On 2/23/2023 4:31 AM, Mark Brown wrote:
On Wed, Feb 22, 2023 at 11:11:42PM +0100, Konrad Dybcio wrote:
Thinking about it again, this seems like something that could be
generalized and introduced into regulator core.. Hardcoding this
will not end well.. Not to mention it'll affect all mp5496-using
boards that are already upstream.
WDYT about regulator-init-microvolts Mark?
The overwhelming majority of devices that have variable voltages
support readback, these Qualcomm firmware devices are pretty much
unique in this regard. We don't want a general property to set a
specific voltage since normally we should be using the
constraints and don't normally need to adjust things immediately
since we can tell what the current voltage is.
This is pretty much just going to be a device specific bodge,
ideally something that does know what the voltage is would be
able to tell us at runtime but if that's not possible then
there's no good options. If the initial voltage might vary based
on board then a device specific DT property might be less
terrible, if it's determined by the regulator the current code
seems fine. Or just leave the current behavour, if the
constraints are accurate then hopefully a temporary dip in
voltage is just inelegant rather than an issue. Indeed the
current behaviour might well save power if you've got a voltage
range configured and nothing actually ever gets round to setting
the voltage (which is depressingly common, people seem keen on
setting voltage ranges even when the voltage is never varied in
practice).
Hi Mark, The initial bootup voltage is actually blown into the OTP
register of the PMIC and it remains the same across boards for IPQ9574
SoC. Initially the SoC runs at 800MHz with a voltage of 875mV set by the
bootloaders. As kernel does not know the initial voltage, during
regulator registration the framework considers the current voltage to be
zero and tries to bring up the regulator to minimum supported voltage of
600mV. This causes the dip which might be of concern in SS parts where
the voltage might be insufficient leading to silent reboots.
Best Regards,
Devi Priya
