Hi,
Michael Grzeschik <mgr@xxxxxxxxxxxxxx> writes:
On Tue, Dec 15, 2020 at 12:24:51PM +0530, Manish Narani wrote:
Add a new driver for supporting Xilinx platforms. This driver is used
for some sequence of operations required for Xilinx USB controllers.
This driver is also used to choose between PIPE clock coming from SerDes
and the Suspend Clock. Before the controller is out of reset, the clock
selection should be changed to PIPE clock in order to make the USB
controller work. There is a register added in Xilinx USB controller
register space for the same.
I tried out this driver with the vanilla kernel on an zynqmp. Without
this patch the USB-Gadget is already acting buggy. In the gadget mode,
some iterations of plug/unplug results to an stalled gadget which will
never come back without a reboot.
With the corresponding code of this driver (reset assert, clk modify,
reset deassert) in the downstream kernels phy driver we found out it is
totaly stable. But using this exact glue driver which should do the same
as the downstream code, the gadget still was buggy the way described
above.
I suspect the difference lays in the different order of operations.
While the downstream code is runing the resets inside the phy driver
which is powered and initialized in the dwc3-core itself. With this glue
layser approach of this patch the whole phy init is done before even
touching dwc3-core in any way. It seems not to have the same effect,
though.
If really the order of operations is limiting us, we probably need
another solution than this glue layer. Any Ideas?
might be a good idea to collect dwc3 trace events. Can you do that?
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