Hi Felipe,
Thinh Nguyen wrote:
Felipe Balbi wrote:
Hi,
Thinh Nguyen Thinh.Nguyen@synopsys.com writes:
Thinh Nguyen Thinh.Nguyen@synopsys.com writes:
From: Yu Chen chenyu56@huawei.com From: John Stultz john.stultz@linaro.org
According to the programming guide, to switch mode for DRD controller, the driver needs to do the following.
To switch from device to host:
- Reset controller with GCTL.CoreSoftReset
- Set GCTL.PrtCapDir(host mode)
- Reset the host with USBCMD.HCRESET
- Then follow up with the initializing host registers sequence
To switch from host to device:
- Reset controller with GCTL.CoreSoftReset
- Set GCTL.PrtCapDir(device mode)
- Reset the device with DCTL.CSftRst
- 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.
This is for DRD only. It should not impact the old OTG flow. We already have the check in place.
I thought I checked for OTG, but I missed it. I think v3 should cover it.
Thanks, Thinh