On Mon, May 24, 2021 at 01:51:51PM +0800, Chunfeng Yun wrote:

On Fri, 2021-05-21 at 15:20 +0200, Thierry Reding wrote:

quoted

On Wed, May 19, 2021 at 02:39:46PM +0800, Chunfeng Yun wrote:

quoted

Vbus is already an optional supply, if the vbus-supply is not
provided in DTS, will use a dummy regulator,

That statement is not entirely correct. The dummy regulator is
substituted only if the supply is in fact not optional. The idea behind
that is to allow DTS files that don't specify all required regulators to
get away with it, based on the assumption that the supply is one of
those always-on supplies that are often not described in DTS.

Yes, you are right.
But from the point of result, it indeed can help to handle the absent
regulator.

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the warning log is as below:
"supply vbus not found, using dummy regulator"

And the reason why we get that warning is to point out that the DTS has
a bug and that it should be fixed (by adding a proper regulator to take
the place of the dummy).

quoted

This reverts commit 4ddf1ac79e5f082451cd549283d2eb7559ab6ca9.

But if you read the description of that commit, the purpose of that
patch was in fact to make the supply completely optional in the case
where we already have the VBUS supply specified for the USB port that
the connector is parented to.

Could you please give an example you mentioned?

You can find examples of this in these:

	arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi
	arch/arm64/boot/dts/nvidia/tegra210-p3450-0000.dts
	arch/arm64/boot/dts/nvidia/tegra186-p2771-0000.dts

It seems prefer to provide vbus supply in connector instead of port
according to dt-binding

My recollection is that the above (or at least some of them) predate USB
connectors.

It's possible that we could convert the above to have the VBUS supply
listed in the connector instead of the port. However, since we have to
preserve backwards compatibility with older device trees, we can't
revert the commit anyway.

Thierry