[PATCH v6 1/1] usb: xhci: Add Clear_TT_Buffer

[Jim Lin]

USB 2.0 specification chapter 11.17.5 says "as part of endpoint halt
processing for full-/low-speed endpoints connected via a TT, the host
software must use the Clear_TT_Buffer request to the TT to ensure
that the buffer is not in the busy state".

In our case, a full-speed speaker (ConferenceCam) is behind a high-
speed hub (ConferenceCam Connect), sometimes once we get STALL on a
request we may continue to get STALL with the folllowing requests,
like Set_Interface.

Solution is for XHCI driver to invoke usb_hub_clear_tt_buffer() to
send Clear_TT_Buffer request to the hub of the device for the
following Set_Interface requests to the device to get ACK
successfully.

The Clear_TT_Buffer request sent to the hub includes the address of
the LS/FS child device in wValue field. usb_hub_clear_tt_buffer()
uses udev->devnum to set the address wValue. This won't work for
devices connected to xHC.

For other host controllers udev->devnum is the same as the address of
the usb device, chosen and set by usb core. With xHC the controller
hardware assigns the address, and won't be the same as devnum.

In the fix we get that address from slot context if it's XHC.

Signed-off-by: Jim Lin <jilin@xxxxxxxxxx>
---
v2: xhci_clear_tt_buffer_complete: add static, shorter indentation
    , remove its claiming in xhci.h
v3: Add description for clearing_tt (xhci.h)
v4: Remove clearing_tt flag because hub_tt_work has hub->tt.lock
    to protect for Clear_TT_Buffer to be run serially.
    Remove xhci_clear_tt_buffer_complete as it's not necessary.
    Same reason as the above.
    Extend usb_hub_clear_tt_buffer parameter
v5: Not extending usb_hub_clear_tt_buffer parameter
    Add description.
v6: Remove unused parameter slot_id from xhci_clear_hub_tt_buffer

 drivers/usb/core/hub.c       | 17 ++++++++++++++++-
 drivers/usb/host/xhci-ring.c | 12 ++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 15a2934dc29d..00d994908217 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -35,6 +35,7 @@
 
 #include "hub.h"
 #include "otg_whitelist.h"
+#include "../host/xhci.h"
 
 #define USB_VENDOR_GENESYS_LOGIC		0x05e3
 #define HUB_QUIRK_CHECK_PORT_AUTOSUSPEND	0x01
@@ -858,6 +859,10 @@ int usb_hub_clear_tt_buffer(struct urb *urb)
 	struct usb_tt		*tt = udev->tt;
 	unsigned long		flags;
 	struct usb_tt_clear	*clear;
+	struct xhci_hcd *xhci;
+	struct xhci_virt_device *dev;
+	struct xhci_slot_ctx *slot_ctx;
+	int devnum;
 
 	/* we've got to cope with an arbitrary number of pending TT clears,
 	 * since each TT has "at least two" buffers that can need it (and
@@ -873,7 +878,17 @@ int usb_hub_clear_tt_buffer(struct urb *urb)
 	/* info that CLEAR_TT_BUFFER needs */
 	clear->tt = tt->multi ? udev->ttport : 1;
 	clear->devinfo = usb_pipeendpoint (pipe);
-	clear->devinfo |= udev->devnum << 4;
+	/* If slot_id is nonzero, then it's XHCI */
+	if (udev->slot_id) {
+		xhci = hcd_to_xhci(bus_to_hcd(udev->bus));
+		dev = xhci->devs[udev->slot_id];
+		slot_ctx = xhci_get_slot_ctx(xhci, dev->out_ctx);
+		/* Device address is assigned by XHC */
+		devnum = (int) le32_to_cpu(slot_ctx->dev_state) &
+			DEV_ADDR_MASK;
+		clear->devinfo |= devnum << 4;
+	} else
+		clear->devinfo |= udev->devnum << 4;
 	clear->devinfo |= usb_pipecontrol(pipe)
 			? (USB_ENDPOINT_XFER_CONTROL << 11)
 			: (USB_ENDPOINT_XFER_BULK << 11);
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9215a28dad40..739737faf752 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1786,6 +1786,17 @@ struct xhci_segment *trb_in_td(struct xhci_hcd *xhci,
 	return NULL;
 }
 
+static void xhci_clear_hub_tt_buffer(struct xhci_hcd *xhci, struct xhci_td *td)
+{
+	/*
+	 * As part of low/full-speed endpoint-halt processing
+	 * we must clear the TT buffer (USB 2.0 specification 11.17.5).
+	 */
+	if (td->urb->dev->tt && !usb_pipeint(td->urb->pipe) &&
+	    (td->urb->dev->tt->hub != xhci_to_hcd(xhci)->self.root_hub))
+		usb_hub_clear_tt_buffer(td->urb);
+}
+
 static void xhci_cleanup_halted_endpoint(struct xhci_hcd *xhci,
 		unsigned int slot_id, unsigned int ep_index,
 		unsigned int stream_id, struct xhci_td *td,
@@ -1804,6 +1815,7 @@ static void xhci_cleanup_halted_endpoint(struct xhci_hcd *xhci,
 	if (reset_type == EP_HARD_RESET) {
 		ep->ep_state |= EP_HARD_CLEAR_TOGGLE;
 		xhci_cleanup_stalled_ring(xhci, ep_index, stream_id, td);
+		xhci_clear_hub_tt_buffer(xhci, td);
 	}
 	xhci_ring_cmd_db(xhci);
 }
-- 
2.1.4