+/*
+ * Calculates Frame ID field of the isochronous TRB identifies the
+ * target frame that the Interval associated with this Isochronous
+ * Transfer Descriptor will start on. Refer to 4.11.2.5 in 1.1 spec.
+ *
+ * Returns actual frame id on success, negative value on error.
+ */
+static int xhci_get_isoc_frame_id(struct xhci_hcd *xhci,
+ struct urb *urb, int index)
+{
+ int start_frame, ist, ret = 0;
+ int start_frame_id, end_frame_id, current_frame_id;
+
+ if (urb->dev->speed == USB_SPEED_LOW ||
+ urb->dev->speed == USB_SPEED_FULL)
+ start_frame = urb->start_frame + index * urb->interval;
+ else
+ start_frame = (urb->start_frame + index * urb->interval) >> 3;
+
+ /* Isochronous Scheduling Threshold (IST, bits 0~3 in HCSPARAMS2):
+ *
+ * If bit [3] of IST is cleared to '0', software can add a TRB no
+ * later than IST[2:0] Microframes before that TRB is scheduled to
+ * be executed.
+ * If bit [3] of IST is set to '1', software can add a TRB no later
+ * than IST[2:0] Frames before that TRB is scheduled to be executed.
+ */
+ ist = HCS_IST(xhci->hcs_params2) & 0x7;
+ if (HCS_IST(xhci->hcs_params2) & (1 << 3))
+ ist <<= 3;
+
+ /* Software shall not schedule an Isoch TD with a Frame ID value that
+ * is less than the Start Frame ID or greater than the End Frame ID,
+ * where:
+ *
+ * End Frame ID = (Current MFINDEX register value + 895 ms.) MOD 2048
+ * Start Frame ID = (Current MFINDEX register value + IST + 1) MOD 2048
+ *
+ * Both the End Frame ID and Start Frame ID values are calculated
+ * in microframes. When software determines the valid Frame ID value;
+ * The End Frame ID value should be rounded down to the nearest Frame
+ * boundary, and the Start Frame ID value should be rounded up to the
+ * nearest Frame boundary.
+ */
+ current_frame_id = readl(&xhci->run_regs->microframe_index);
+ start_frame_id = roundup(current_frame_id + ist + 1, 8);
+ end_frame_id = rounddown(current_frame_id + 895 * 8, 8);
+
+ start_frame &= 0x7ff;
+ start_frame_id = (start_frame_id >> 3) & 0x7ff;
+ end_frame_id = (end_frame_id >> 3) & 0x7ff;
+
+ xhci_dbg(xhci, "%s: index %d, reg 0x%x start_frame_id 0x%x, end_frame_id 0x%x, start_frame 0x%x\n",
+ __func__, index, readl(&xhci->run_regs->microframe_index),
+ start_frame_id, end_frame_id, start_frame);
+
+ if (start_frame_id < end_frame_id) {
+ if (start_frame > end_frame_id ||
+ start_frame < start_frame_id)
+ ret = -EINVAL;
+ } else if (start_frame_id > end_frame_id) {
+ if ((start_frame > end_frame_id &&
+ start_frame < start_frame_id))
+ ret = -EINVAL;
+ } else {
+ ret = -EINVAL;
+ }
+
+ if (index == 0) {
+ if (ret == -EINVAL || start_frame == start_frame_id) {
+ start_frame = start_frame_id + 1;
+ if (urb->dev->speed == USB_SPEED_LOW ||
+ urb->dev->speed == USB_SPEED_FULL)
+ urb->start_frame = start_frame;
+ else
+ urb->start_frame = start_frame << 3;
+ ret = 0;
+ }
+ }
+
+ if (ret) {
+ xhci_warn(xhci, "Frame ID %d (reg %d, index %d) beyond range (%d, %d)\n",
+ start_frame, current_frame_id, index,
+ start_frame_id, end_frame_id);
+ xhci_warn(xhci, "Ignore frame ID field, use SIA bit instead\n");
+ return ret;
+ }
+
+ return start_frame;
+}
+