Merge tag 'usb-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb

Pull USB / PHY updates from Greg KH:
 "Here is the big USB and PHY driver pull request for 5.3-rc1.

  Lots of stuff here, all of which has been in linux-next for a while
  with no reported issues. Nothing is earth-shattering, just constant
  forward progress for more devices supported and cleanups and small
  fixes:

   - USB gadget driver updates and fixes

   - new USB gadget driver for some hardware, followed by a quick revert
     of those patches as they were not ready to be merged...

   - PHY driver updates

   - Lots of new driver additions and cleanups with a few fixes mixed
     in"

* tag 'usb-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (145 commits)
  Revert "usb: gadget: storage: Remove warning message"
  Revert "dt-bindings: add binding for USBSS-DRD controller."
  Revert "usb:gadget Separated decoding functions from dwc3 driver."
  Revert "usb:gadget Patch simplify usb_decode_set_clear_feature function."
  Revert "usb:gadget Simplify usb_decode_get_set_descriptor function."
  Revert "usb:cdns3 Add Cadence USB3 DRD Driver"
  Revert "usb:cdns3 Fix for stuck packets in on-chip OUT buffer."
  usb :fsl: Change string format for errata property
  usb: host: Stops USB controller init if PLL fails to lock
  usb: linux/fsl_device: Add platform member has_fsl_erratum_a006918
  usb: phy: Workaround for USB erratum-A005728
  usb: fsl: Set USB_EN bit to select ULPI phy
  usb: Handle USB3 remote wakeup for LPM enabled devices correctly
  drivers/usb/typec/tps6598x.c: fix 4CC cmd write
  drivers/usb/typec/tps6598x.c: fix portinfo width
  usb: storage: scsiglue: Do not skip VPD if try_vpd_pages is set
  usb: renesas_usbhs: add a workaround for a race condition of workqueue
  usb: gadget: udc: renesas_usb3: remove redundant assignment to ret
  usb: dwc2: use a longer AHB idle timeout in dwc2_core_reset()
  USB: gadget: function: fix issue Unneeded variable: "value"
  ...

1 files changed, 53 insertions, 0 deletions

diff --git a/Documentation/usb/dwc3.rst b/Documentation/usb/dwc3.rst
new file mode 100644
index 000000000000..f94a7ba16573
--- /dev/null
+++ b/Documentation/usb/dwc3.rst
@@ -0,0 +1,53 @@
+===========
+DWC3 driver
+===========
+
+
+TODO
+~~~~
+
+Please pick something while reading :)
+
+- Convert interrupt handler to per-ep-thread-irq
+
+  As it turns out some DWC3-commands ~1ms to complete. Currently we spin
+  until the command completes which is bad.
+
+  Implementation idea:
+
+  - dwc core implements a demultiplexing irq chip for interrupts per
+    endpoint. The interrupt numbers are allocated during probe and belong
+    to the device. If MSI provides per-endpoint interrupt this dummy
+    interrupt chip can be replaced with "real" interrupts.
+  - interrupts are requested / allocated on usb_ep_enable() and removed on
+    usb_ep_disable(). Worst case are 32 interrupts, the lower limit is two
+    for ep0/1.
+  - dwc3_send_gadget_ep_cmd() will sleep in wait_for_completion_timeout()
+    until the command completes.
+  - the interrupt handler is split into the following pieces:
+
+    - primary handler of the device
+      goes through every event and calls generic_handle_irq() for event
+      it. On return from generic_handle_irq() in acknowledges the event
+      counter so interrupt goes away (eventually).
+
+    - threaded handler of the device
+      none
+
+    - primary handler of the EP-interrupt
+      reads the event and tries to process it. Everything that requires
+      sleeping is handed over to the Thread. The event is saved in an
+      per-endpoint data-structure.
+      We probably have to pay attention not to process events once we
+      handed something to thread so we don't process event X prio Y
+      where X > Y.
+
+    - threaded handler of the EP-interrupt
+      handles the remaining EP work which might sleep such as waiting
+      for command completion.
+
+  Latency:
+
+   There should be no increase in latency since the interrupt-thread has a
+   high priority and will be run before an average task in user land
+   (except the user changed priorities).