[PATCH v3 1/3] usb: xhci: add quirk flag for broken PED bits

[Roger Quadros <rogerq@ti.com>]

From: Felipe Balbi <balbi@ti.com>

Some devices from Texas Instruments [1] suffer from
a silicon bug where Port Enabled/Disabled bit
should not be used to silence an erroneous device.

The bug is so that if port is disabled with PED
bit, an IRQ for device removal (or attachment)
will never fire.

Just for the sake of completeness, the actual
problem lies with SNPS USB IP and this affects
all known versions up to 3.00a. A separate
patch will be added to dwc3 to enabled this
quirk flag if version is <= 3.00a.

[1] - AM572x Silicon Errata http://www.ti.com/lit/er/sprz429j/sprz429j.pdf
Section i896— USB xHCI Port Disable Feature Does Not Work

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
---
 drivers/usb/host/xhci-hub.c | 6 ++++++
 drivers/usb/host/xhci.h     | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 0ef1690..1d41637 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -458,6 +458,12 @@ static void xhci_disable_port(struct usb_hcd *hcd, struct xhci_hcd *xhci,
 		return;
 	}
 
+	if (xhci->quirks & XHCI_BROKEN_PORT_PED) {
+		xhci_dbg(xhci,
+			 "Broken Port Enabled/Disabled, ignoring port disable request.\n");
+		return;
+	}
+
 	/* Write 1 to disable the port */
 	writel(port_status | PORT_PE, addr);
 	port_status = readl(addr);
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index f945380..585af71 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1656,6 +1656,9 @@ struct xhci_hcd {
 #define XHCI_SSIC_PORT_UNUSED	(1 << 22)
 #define XHCI_NO_64BIT_SUPPORT	(1 << 23)
 #define XHCI_MISSING_CAS	(1 << 24)
+/* For controller with a broken Port Disable implementation */
+#define XHCI_BROKEN_PORT_PED	(1 << 25)
+
 	unsigned int		num_active_eps;
 	unsigned int		limit_active_eps;
 	/* There are two roothubs to keep track of bus suspend info for */
-- 
2.7.4