Messages in this thread | | | Subject | Re: [PATCH v1 2/2] usb: tegra: Move UTMI-pads reset from ehci-tegra to tegra-phy | From | Dmitry Osipenko <> | Date | Mon, 11 Dec 2017 16:31:39 +0300 |
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On 11.12.2017 13:25, Thierry Reding wrote: > On Mon, Dec 11, 2017 at 02:07:38AM +0300, Dmitry Osipenko wrote: >> UTMI pads are shared by USB controllers and reset of UTMI pads is shared >> with the reset of USB1 controller. Currently reset of UTMI pads is done by >> the EHCI driver and ChipIdea UDC works because EHCI driver always happen >> to be probed first. Move reset controls from ehci-tegra to tegra-phy in >> order to resolve the problem. >> >> Signed-off-by: Dmitry Osipenko <digetx@gmail.com> >> --- >> drivers/usb/host/ehci-tegra.c | 87 ++++++++++++++++++--------------------- >> drivers/usb/phy/phy-tegra-usb.c | 46 +++++++++++++++++++++ >> include/linux/usb/tegra_usb_phy.h | 2 + >> 3 files changed, 87 insertions(+), 48 deletions(-) > > I don't think we can do this. For one I don't think shared resets are > going to work here because you really won't ever be able to reset after > two devices have requested the same reset.
Ah, indeed. Originally I had the reset being done in the probe, but then changed it in the last minute without proper testing. Good catch! I'll revert back patch to the origin.
Second, utmip_pad_close() > could be called at any point and it will have the side-effect of either > not doing a reset at all (because it is shared) or resetting the USBD > controller at the same time.
utmip_pad_close() is only called on tegra-phy driver removal, so it is absolutely fine.
> We've been over this code a great deal over the years. I'd love it to be > simpler, but every time we tried to simplify it, things broke.
Well, the current code is already broken quite severely because now we have two users of the tegra-phy: ehci-tegra and chipidea-tegra. Things brake if host driver is loaded after the UDC because host would reset the UDC. And also pads won't be reset if ehci-tegra isn't loaded at all.
Shared reset seems to be a perfect solution for us and of course it requires extra carefulness.
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