Hi Rob and all,

On Fri, 2019-03-15 at 00:44 +0800, Rob Herring wrote:

On Thu, Mar 14, 2019 at 3:46 AM Marc Gonzalez [off-list ref] wrote:

quoted

On 13/03/2019 20:48, Rob Herring wrote:

Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt mentions:
- <name>-fixed-regulator : boolean property specifying that <name>-supply is a fixed regulator.

quoted

There are no users of that property in tree and doesn't look like
adding it was ever reviewed. We have standard ways to handle this and
don't need a custom property.

FWIW, it seems to come from downstream:

The question would be is downstream compliant with the upstream
binding. If so, then we shouldn't really break things as that's just
out of tree which is fine.

Or we just need a better explanation of why it is needed. MMC has some
properties related to card voltages for example. Maybe the need is
similar.

For short-term, could this patch series be merged without "vcc" related
property defined in dt-bindings (like PATCH V5 does)? Or using
"vcc-supply" along with "vcc-fixed-regulator" with a detailed
explanation can be accepted?

ufs-mediatek can work fine without "vcc" related property but with a
limitation that driver cannot control "vcc" power which is enabled
by-default on MediaTek chipsets.

For long-term, it seems to me that "<name>-fixed-regulator" can be
removed from both dt-bindings and UFS driver without impact, even for
downstream usage found by Marc.

If "<name>-fixed-regulator" property is defined in device tree, such
regulator will skip "current limit" assignment from
"<name>-max-microamp" property, and voltage range assignment from
"vcc-supply-lp8" property (for vcc, vccq, and vccq2 only). If driver can
handle above both cases correctly, "<name>-fixed-regulator" can be
removed.

In MediaTek chipsets, "vcc-supply" can ignore above two properties.
However if "vcc-fixed-regulator" is not added, driver will get fail
during device tree probing due to undefined "vcc-max-microamp".

If our target is removing "<name>-fixed-regulator", we could try to fix
and resolve above all. And if we do not merge "vcc" related property
this time, after that we can add "vcc-supply" back to dt-bindings to
provide vcc control capability in ufs-mediatek driver.

Would you please provide any suggestions?

Rob