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    SubjectRe: [PATCH V3 4/6] usb: ohci-platform: Add support for Broadcom STB SoC's
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    On 11/7/18 12:29 PM, Florian Fainelli wrote:
    > On 11/7/18 8:27 AM, Alan Stern wrote:
    >> On Wed, 7 Nov 2018, Al Cooper wrote:
    >>
    >>> On 11/7/18 10:23 AM, Alan Stern wrote:
    >>>> On Tue, 6 Nov 2018, Florian Fainelli wrote:
    >>>>
    >>>>> On 11/6/18 1:40 PM, Al Cooper wrote:
    >>>>>> On 11/6/18 11:08 AM, Alan Stern wrote:
    >>>>>>> On Mon, 5 Nov 2018, Al Cooper wrote:
    >>>>>>>
    >>>>>>>> Add support for Broadcom STB SoC's to the ohci platform driver.
    >>>>>>>>
    >>>>>>>> Signed-off-by: Al Cooper <alcooperx@gmail.com>
    >>>>>>>> ---
    >>>>>>>
    >>>>>>>> @@ -177,6 +189,8 @@ static int ohci_platform_probe(struct
    >>>>>>>> platform_device *dev)
    >>>>>>>>           ohci->flags |= OHCI_QUIRK_FRAME_NO;
    >>>>>>>>       if (pdata->num_ports)
    >>>>>>>>           ohci->num_ports = pdata->num_ports;
    >>>>>>>> +    if (pdata->suspend_without_phy_exit)
    >>>>>>>> +        hcd->suspend_without_phy_exit = 1;
    >>>>>>>
    >>>>>>> Sorry if I missed this in the earlier discussions...  Is there any
    >>>>>>> possibility of adding a DT binding that could express this requirement,
    >>>>>>> instead of putting it in the platform data?
    >>>>>>>
    >>>>>>> Alan Stern
    >>>>>>>
    >>>>>>
    >>>>>> Alan,
    >>>>>>
    >>>>>> That was my original approach but internal review suggested that I use
    >>>>>> pdata instead. Below is my original patch for:
    >>>>>
    >>>>> And the reason for that suggestion was really because it was percevied
    >>>>> as encoding a driver behavior as a Device Tree property as opposed to
    >>>>> describing something that was inherently and strictly a hardware
    >>>>> behavior (therefore suitable for Device Tree).
    >>>>
    >>>> Right. The best way to approach this problem is to identify and
    >>>> characterize the hardware behavior which makes this override necessary.
    >>>> Then _that_ can be added to DT, since it will be a property of the
    >>>> hardware rather than of the driver.
    >>>>
    >>>>>> Add the ability to skip calling the PHY's exit routine on suspend
    >>>>>> and the PHY's init routine on resume. This is to handle a USB PHY
    >>>>>> that should have it's power_off function called on suspend but cannot
    >>>>>> have it's exit function called because on exit it will disable the
    >>>>>> PHY to the point where register accesses to the Host Controllers
    >>>>>> using the PHY will be disabled and the host drivers will crash.
    >>>>
    >>>> What's special about this PHY? Why does the exit function mess the PHY
    >>>> up? Or to put it another way, why doesn't the exit function mess up
    >>>> other PHYs in the same way?
    >>>>
    >>>> For that matter, can we change the code so that suspend doesn't call
    >>>> the exit function for _any_ PHY? Will just calling the power_off
    >>>> function be good enough? If not, then why not?
    >>>>
    >>>> Alan Stern
    >>>>
    >>>
    >>> In our USB hardware the USB PHY supplies a clock for the EHCI/OHCI and
    >>> XHCI host controllers and if the PHY is totally shut down the EHCI, OHCI
    >>> and XHCI registers will cause an exception if accessed and cause the
    >>> EHCI, OHCI and XHCI drivers to crash. There is always talk of fixing
    >>> this in the hardware by adding an aux clock that will takeover when the
    >>> PHY clock is shut down, but this hasn't happened yet. It seems like
    >>> "exit on suspend" still makes sense on systems that don't have this
    >>> problem (additional power savings?) so removing the exit on suspend for
    >>> all systems is not a good idea.
    >>
    >> Then in theory you should be able to add a Device Tree property which
    >> says that the PHY provides a clock for the USB host controller. That
    >> is strictly a property of the hardware; it has nothing to do with the
    >> driver. Therefore it is appropriate for DT.
    >
    > The very compatible string that is being allocated/defined for this
    > controller carries that information already, that is, if you probe a
    > "brcm,bcm7445-ohci" compatible then that means the controller has a
    > dependency on the PHY to supply its clock.
    >
    > Adding a property vs. keying on the compatible string makes sense if you
    > know there is at least a second consumer of that property (unless we
    > make it a broadcom specific property, in which case, it really is
    > redundant with the compatible string).
    >
    > Anyway, my grudge with that property was the name chosen initially,
    > which included an action to be performed by an implementation as opposed
    > to something purely descriptive. E.g: 'phy-supplies-clock' might be okay.
    >
    >>
    >> Wouldn't this solve your issue?
    >
    > It would not change much except that there is no need to much with
    > ohci-platform.c anymore, but ultimately that property needs to be read
    > by ohci-hcd.c and acted on, which would likely lead to the same amount
    > of changes as those present in patch #2 currently.
    >
    We also need this functionality in the EHCI and XHCI drivers and it's
    not the ohci-hcd.c module that needs to know, it's the core/phy.c module
    called from core/hcd.c.

    Al

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