[PATCH 4/7] phy: meson: add USB2 PHY support for Meson8b and GXBB

Martin Blumenstingl [off-list ref] writes:

On Fri, Sep 9, 2016 at 5:33 PM, Kevin Hilman [off-list ref] wrote:

quoted

However, the problem with all of the solutions proposed (runtime PM ones
included) is that we're forcing a board-specific design issue (2 devices
sharing a reset line) into a driver that should not have any
board-specific assumptions in it.

For example, if this driver is used on another platform where different
PHYs have different reset lines, then one of them (the unlucky one who
is not probed first) will never get reset.  So any form of per-device
ref-counting is not a portable solution.

maybe we should also consider Ben's solution: he played with the USB
PHY on his Meson8b board. His approach was to have only one USB PHY
driver instance which exposes two PHYs.
The downside of this: the driver would have to know the offset of the
PHYs (0x0 for the first PHY, 0x20 for the second), but we could handle
the reset using runtime PM without any hacks.

I checked the USB PHY reference driver: it seems that there will be a
new USB PHY with the GXL/GXM SoCs.
So maybe we could live with the assumption that the PHYs are at
consecutive addresses.

But isn't that also forcing us to make board-specific assumptions inside
the driver.

Kevin