On Mon, Oct 17, 2016 at 06:56:16PM -0700, Stephen Boyd wrote: > The qcom HSIC ULPI phy doesn't have any bits set in the vendor or > product ID registers. This makes it impossible to make a ULPI > driver match against the ID registers. Add support to discover > the ULPI phys via DT help alleviate this problem. In the DT case, > we'll look for a ULPI bus node underneath the device registering > the ULPI viewport (or the parent of that device to support > chipidea's device layout) and then match up the phy node > underneath that with the ULPI device that's created. > > The side benefit of this is that we can use standard properties > in the phy node like clks, regulators, gpios, etc. because we > don't have firmware like ACPI to turn these things on for us. And > we can use the DT phy binding to point our phy consumer to the > phy provider. > > The ULPI bus code supports native enumeration by reading the > vendor ID and product ID registers at device creation time, but > we can't be certain that those register reads will succeed if the > phy is not powered up. To avoid any problems with reading the ID > registers before the phy is powered we fallback to DT matching > when the ID reads fail. > > If the ULPI spec had some generic power sequencing for these > registers we could put that into the ULPI bus layer and power up > the device before reading the ID registers. Unfortunately this > doesn't exist and the power sequence is usually device specific. > By having the device matched up with DT we can avoid this > problem. > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx> > Cc: <devicetree@xxxxxxxxxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > Signed-off-by: Stephen Boyd <stephen.boyd@xxxxxxxxxx> Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx> -- heikki -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
