Hi,
On 15-01-15 23:04, Maxime Ripard wrote:
On Fri, Jan 16, 2015 at 12:54:58AM +0800, Chen-Yu Tsai wrote:
Hi,
On Wed, Jan 14, 2015 at 3:42 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Hi,
On 13-01-15 17:46, Maxime Ripard wrote:
On Tue, Jan 13, 2015 at 10:39:01AM +0100, Hans de Goede wrote:
Hi ChenYu, Maxime,
During the review of a few dts files for new boards Maxime asked me to
use
axp209.dtsi to avoid the standard axp209 "boilerplate" present in most
boards using the axp209 pmic.
But axp209.dtsi includes empty regulator nodes, e.g. :
reg_dcdc3: dcdc3 {
regulator-name = "dcdc3";
};
This is a BAD idea, the presence of these empty nodes causes the
axp20x-regulator driver to actually register regulators for them,
and then on late_init the regulator subsys turns them off, since
they have absolutely no constraints set (nor users registered)
and the regulator subsys assumes that when devicetree is used their
is always a compete set of constraints and that thus turning them
off is safe.
So when I switched to using axp209.dtsi for the bananapro.dts,
and booted the bananapro this is the last message I got from the
kernel while booting:
[ 2.314014] dcdc3: disabling
And away went our DRAM power-supply, oops.
So for dcdc2 (CPU) and dcdc3 (DRAM), the boilerplate
should contain reasonable constraints (eg the operating range
from the datasheet)
Indeed.
and an always-on property.
I disagree. The regulator disabling is a feature, and how the board is
wired is, well, up to the board.
And here I was thinking you wanted to reduce the amount of boilerplate
in our dts files ..
IOW I disagree with your disagreeing all boards we know of have dcdc2
wired to Vcpu and dcdc3 wired to Vddr, so not having this in the dtsi
will lead to a lot of extra boilerplate in each dts file. We're not
talking about our main dtsi file here, if we ever encounter a board
which is wired in a different way, then its dts can simply not use
axp209.dtsi and instead define the nodes itself, it needs to do that
anyways if we do include the standard CPU and DDR constrains in the
dtsi since those will not make sense either in that case.
I think Maxime is only disagreeing to the "always-on" part. And I
somewhat agree with him, but on a technical level. It doesn't seem
possible to negate at the board level the "always-on" set in the dtsi,
or it is not obvious to me how to do so. With properties with values
you just set a new value. How do you "unset" a boolean flag?
You don't, but Hans suggestion was to not use the DTSI then and define
the nodes yourself in your DTS.
Another solution would be if this case comes up at some point to just
push the always-on constraints to the boards, but assume for now that
all boards will want it to be always on.
As for the constraints, I think we can agree that everyone will use
the reference design if they choose to include the PMIC on a board.
I'm not sure to get what you mean here. The PMIC has constraints of
its own (the min/max voltage it can deliver), and boards will have
some too (ie the min/max voltage the components can handle). So I
guess we will end up with constraints defined at both levels.
If an always-on property is needed, then it's in the DTS, not in the
AXP DTSI.
The ldo-s are trickier, since we simply do not know how those
are used, I think ldo2 is used for Avcc on most boards, so it
too should be always on, since almost any board will have some
analog parts on it (be it the ir receiver, lradc, rtp, lvds, vga,
or analog audio in/out). Assuming that we're willing to assume
that ldo2 is used this way, we should give it matching constraints
and always mark it always-on.
Ideally, all the drivers that have a analogic component should have a
reference to the regulator they use. But again, at the board
level. And more realistically, putting always-on should also happen at
the board level.
As for ldo3 - 5 I've no idea when / for what these are used, but
if we do not know it is better to just leave them be then to turn
them off IMHO, so we should remove the nodes for these from axp209.dtsi
Anyways sorting this all out is going to take some time, so I'm
not going to use axp209.dtsi in dts files for new boards for now.
I'm afraid it's an "all or nothing" situation.
No it is not, the PMIC is a mfd, and we can use some of its functions
fine without actually loading the regulator bits. This is already
done on most boards with the axp209, even without touching the regulators
it is nice to have the axp209 mfd driver loaded so that we get support
for the powerbutton, and support for poweroff, esp. the latter is quite
nice to have.
I agree that a) the PMIC is an mfd, and b) we can use other bits without
loading the regulator bits. But if adding the regulator bits results in
some sort of crash or issue, just because some regulator got turned off,
it seems to me that the dt is not accurately describing the hardware.
Yeah, that's kind of the same argument than the one we had with
simplefb clocks. So I guess we can agree that we can allow the MFD
part alone to work, but if regulator support is introduced, then *all*
regulators must be described accurately.
Hmm, I would prefer to have all listed regulators described accurately,
if we do not know how a regulator is used it may be best to just leave it
out (leaving it at whatever setting the bootloader has configured it) AFAIK
there is no technical reason why we must describe all or no regulators.
Regards,
Hans
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