Messages in this thread | | | Subject | Re: [PATCH V3 4/6] usb: ohci-platform: Add support for Broadcom STB SoC's | From | Al Cooper <> | Date | Wed, 7 Nov 2018 12:40:57 -0500 |
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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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