kern: usb: Poll USBSTS.CNR after reset

The host needs to wait for the controller to be ready by polling the CNR
bit as per section 4.2 of the spec

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 17 insertions, 0 deletions

diff --git a/src/sys/include/io/usb/xhciregs.h b/src/sys/include/io/usb/xhciregs.h
index ebaf5d7..85a8630 100644
--- a/src/sys/include/io/usb/xhciregs.h
+++ b/src/sys/include/io/usb/xhciregs.h
@@ -77,6 +77,12 @@ struct __packed xhci_opregs {
  */
 #define USBCMD_HCRST BIT(1)     /* Host controller reset */
 
+/*
+ * USB status register bits
+ *
+ * See section 5.4.2 of the xHCI spec
+ */
+#define USBSTS_CNR  BIT(11)     /* Controller not ready */
 
 /*
  * Macros to get various register spaces
diff --git a/src/sys/io/usb/hcd/xhci.c b/src/sys/io/usb/hcd/xhci.c
index 8d3b0a0..f363bcf 100644
--- a/src/sys/io/usb/hcd/xhci.c
+++ b/src/sys/io/usb/hcd/xhci.c
@@ -116,6 +116,17 @@ xhci_reset_hc(struct xhci_hcd *hcd)
         return error;
     }
 
+    /*
+     * Section 4.2 of the XHCI spec states that we also
+     * need to wait for the controller to be ready via
+     * the USBSTS.CNR (controller not ready) bit
+     */
+    error = xhci_poll32(&opregs->usbcmd, USBSTS_CNR, false);
+    if (error < 0) {
+        pr_trace("hang waiting for controller ready\n");
+        return error;
+    }
+
     return 0;
 }