On Intel platforms, if the debug target is connected with debug
host, enabling DCE bit in command register leads to a port hung
state. In the hung state, the host system will not see a port
connected status bit set. Hence debug target fails to be probed.
The state could be resolved by performing a port reset to the
debug port from the host xHCI. This patch introduces this work
around.
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/usb/early/xhci-dbc.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/usb/xhci-dbc.h | 2 ++
2 files changed, 54 insertions(+)
diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 22a1de9..6b23f09 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -255,6 +255,8 @@ static void __iomem *xdbc_map_pci_mmio(u32 bus,
xdbcp->bar = bar;
xdbcp->xhci_base = base;
xdbcp->xhci_length = sz64;
+ xdbcp->vendor = read_pci_config_16(bus, dev, func, PCI_VENDOR_ID);
+ xdbcp->device = read_pci_config_16(bus, dev, func, PCI_DEVICE_ID);
if (length)
*length = sz64;
@@ -651,6 +653,52 @@ static int xdbc_mem_init(void)
return 0;
}
+static void xdbc_reset_debug_port_callback(int cap_offset, void *data)
+{
+ u8 major;
+ u32 val, port_offset, port_count;
+ u32 cap_length;
+ void __iomem *ops_reg;
+ void __iomem *portsc;
+ int i;
+
+ val = readl(xdbcp->xhci_base + cap_offset);
+ major = (u8) XHCI_EXT_PORT_MAJOR(val);
+
+ /* only reset super-speed port */
+ if (major != 0x3)
+ return;
+
+ val = readl(xdbcp->xhci_base + cap_offset + 8);
+ port_offset = XHCI_EXT_PORT_OFF(val);
+ port_count = XHCI_EXT_PORT_COUNT(val);
+ xdbc_trace("Extcap Port offset %d count %d\n",
+ port_offset, port_count);
+
+ cap_length = readl(xdbcp->xhci_base) & 0xff;
+ ops_reg = xdbcp->xhci_base + cap_length;
+
+ port_offset--;
+ for (i = port_offset; i < (port_offset + port_count); i++) {
+ portsc = ops_reg + 0x400 + i * 0x10;
+ val = readl(portsc);
+ /* reset the port if CCS bit is cleared */
+ if (!(val & 0x1))
+ writel(val | (1 << 4), portsc);
+ }
+}
+
+static void xdbc_reset_debug_port(void)
+{
+ xdbc_walk_excap(xdbcp->bus,
+ xdbcp->dev,
+ xdbcp->func,
+ XHCI_EXT_CAPS_PROTOCOL,
+ false,
+ xdbc_reset_debug_port_callback,
+ NULL);
+}
+
/*
* xdbc_start: start DbC
*
@@ -669,6 +717,10 @@ static int xdbc_start(void)
return -ENODEV;
}
+ /* reset port to avoid bus hang */
+ if (xdbcp->vendor == PCI_VENDOR_ID_INTEL)
+ xdbc_reset_debug_port();
+
/* wait for port connection */
if (handshake(&xdbcp->xdbc_reg->portsc, PORTSC_CCS,
PORTSC_CCS, 5000000, 100) < 0) {
diff --git a/include/linux/usb/xhci-dbc.h b/include/linux/usb/xhci-dbc.h
index 153fb87..fc0ef9a 100644
--- a/include/linux/usb/xhci-dbc.h
+++ b/include/linux/usb/xhci-dbc.h
@@ -128,6 +128,8 @@ struct xdbc_state {
u32 dev;
u32 func;
u8 bar;
+ u16 vendor;
+ u16 device;
void __iomem *xhci_base;
size_t xhci_length;
#define XDBC_PCI_MAX_BUSES 256
--
2.1.4
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