Hi, Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> writes: >> Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> writes: >>> From: Yu Chen <chenyu56@xxxxxxxxxx> >>> From: John Stultz <john.stultz@xxxxxxxxxx> >>> >>> According to the programming guide, to switch mode for DRD controller, >>> the driver needs to do the following. >>> >>> To switch from device to host: >>> 1. Reset controller with GCTL.CoreSoftReset >>> 2. Set GCTL.PrtCapDir(host mode) >>> 3. Reset the host with USBCMD.HCRESET >>> 4. Then follow up with the initializing host registers sequence >>> >>> To switch from host to device: >>> 1. Reset controller with GCTL.CoreSoftReset >>> 2. Set GCTL.PrtCapDir(device mode) >>> 3. Reset the device with DCTL.CSftRst >>> 4. Then follow up with the initializing registers sequence >>> >>> Currently we're missing step 1) to do GCTL.CoreSoftReset and step 3) of >> >> we're not really missing, it was a deliberate choice :-) The only reason >> why we need the soft reset is because host and gadget registers map to >> the same physical space within dwc3 core. If we cache and restore the >> affected registers, we're good ;-) > > It's part of the programming model. I've already discussed with internal > RTL designers. This is needed, and I've provided the discussion we had > prior also. We have several different devices in the wild that need > this. What is the concern? Timing :-) If anyone wants to support OTG spec, it'll be super hard to guarantee the timing mandated by the spec if we have to go through full reset. >> IMHO, that's a better compromise than doing a full soft reset. >> >>> @@ -40,6 +41,8 @@ >>> >>> #define DWC3_DEFAULT_AUTOSUSPEND_DELAY 5000 /* ms */ >>> >>> +static DEFINE_MUTEX(mode_switch_lock); >> >> there are several platforms which more than one DWC3 instance. Sure this >> won't break on such systems? >> > > How? Am I missing something? Please let me know so I can make the change. Again timing :-) Instance 0 swaps role and instance 1 swaps right after. Instance 1 will be waiting for the mutex held by instance 0. -- balbi
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