On 4/16/2021 3:47 AM, Felipe Balbi wrote:

Hi,

Thinh Nguyen [off-list ref] writes:

quoted

From: Yu Chen <chenyu56@huawei.com>
From: John Stultz <redacted>

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
switching from host to device. John Stult reported a lockup issue seen
with HiKey960 platform without these steps[1]. Similar issue is observed
with Ferry's testing platform[2].

So, apply the required steps along with some fixes to Yu Chen's and John
Stultz's version. The main fixes to their versions are the missing wait
for clocks synchronization before clearing GCTL.CoreSoftReset and only
apply DCTL.CSftRst when switching from host to device.

[1] https://lore.kernel.org/linux-usb/20210108015115.27920-1-john.stultz@linaro.org/ (local)
[2] https://lore.kernel.org/linux-usb/0ba7a6ba-e6a7-9cd4-0695-64fc927e01f1@gmail.com/ (local)

Cc: Andy Shevchenko <redacted>
Cc: Ferry Toth <redacted>
Cc: Wesley Cheng <redacted>
Cc: <redacted>
Fixes: 41ce1456e1db ("usb: dwc3: core: make dwc3_set_mode() work properly")
Signed-off-by: Yu Chen <chenyu56@huawei.com>
Signed-off-by: John Stultz <redacted>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

I still have concerns about the soft reset, but I won't block you guys
from fixing Hikey's problem :-)

The only thing I would like to confirm is that this has been verified
with hundreds of swaps happening as quickly as possible. DWC3 should
still be functional after several hundred swaps.

Can someone confirm this is the case? (I'm assuming this can be
scripted)

Hi Thinh/Felipe,

Thanks Thinh for this change.  Will verify this on our platform as well
with a mode switch loop over the weekend.

Thanks
Wesley Cheng
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