On Fri, May 21, 2021 at 03:20:23PM +0200, Thierry Reding wrote:

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.

quoted

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.

So in that case the DTS doesn't have the bug because the VBUS supply is
already specified for the USB port and therefore it doesn't have to be
specified in the USB connector again. In fact, specifying it twice can
lead to a situation where the USB port may not be able to switch the
VBUS supply on or off because the setting might conflict with that of
the USB connector.

So unless there's a real reason why this is needed, I don't think this
should be applied.

I've dropped this from my tree now, thanks.

greg k-h

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