On 21 November 2016 at 16:31, Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> wrote: > On 21.11.2016 09:57, Rafał Miłecki wrote: >> >> Hi Mathias, >> >> On 17 October 2016 at 22:30, Rafał Miłecki <zajec5@xxxxxxxxx> wrote: >>> >>> From: Rafał Miłecki <rafal@xxxxxxxxxx> >>> >>> Broadcom's Northstar XHCI controllers seem to need a special start >>> procedure to work correctly. There isn't any official documentation of >>> this, the problem is that controller doesn't detect any connected >>> devices with default setup. Moreover connecting USB device to controller >>> that doesn't run properly can cause SoC's watchdog issues. >>> >>> A workaround that was successfully tested on multiple devices is to >>> perform a fake doorbell. This patch adds code for doing this and enables >>> it on BCM4708 family. >>> >>> Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx> >>> --- >>> V2: Enable quirk for brcm,bcm4708 machines instead of adding separated >>> binding >>> for it. Thanks Rob for your comment on this. >> >> >> Do you think you can pick & push this one? V2 follows Rob's suggestion >> and he has some DT knowledge for sure, so I guess it should be OK. >> -- > > > Is there some more background information on this? > > I don't have any contacts to Broadcom myself, adding the BMC Kernel Feedback > list to CC. > Maybe someone over there has an errata, documentation or just general > feedback. > > How was this workaround even figured out? ringing the doorbell for the first > device doesn't seem like something found by trial and error, especially > when > xhci specs state that: > > "Software shall not write the Doorbell of an endpoint until after it has > issued a > Configure Endpoint Command for the endpoint and received a successful > Command > Completion Event." > > The whole workaround is a bit intrusive, allocating a fake device, ring a > doorbell for a > fake device in the wrong state, clearing off HSE (host system error) which > should only be set > when things really go bad, some random usleeps, and possible calling > xhci_start() twice. > > I can't take this as is without some more info. Hi (ping) Broadcom guys, could you help us with this USB workaround, please? -- Rafał -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
