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

Kevin Hilman
2016-09-09T17:04:19Z

Martin Blumenstingl <martin.blumenstingl-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> writes:

> On Fri, Sep 9, 2016 at 5:33 PM, Kevin Hilman <khilman-rdvid1DuHRBWk0Htik3J/w@public.gmane.org> wrote:
>> 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
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