The RWE bit of the USB 2.0 PORTPMSC register is supposed to enable
remote wakeup for devices in the lower power link state L1. It has
nothing to do with the device suspend remote wakeup from L2. The RWE
bit is designed to be set once (when USB 2.0 LPM is enabled for the
port) and cleared only when USB 2.0 LPM is disabled for the port.
The xHCI bus suspend method was setting the RWE bit erroneously, and the
bus resume method was clearing it. The xHCI 1.0 specification with
errata up to Aug 12, 2012 says in section 4.23.5.1.1.1 "Hardware
Controlled LPM":
"While Hardware USB2 LPM is enabled, software shall not modify the
HIRDBESL or RWE fields of the USB2 PORTPMSC register..."
If we have previously enabled USB 2.0 LPM for a device, that means when
the USB 2.0 bus is resumed, we violate the xHCI specification by
clearing RWE. It also means that after a bus resume, the host would
think remote wakeup is disabled from L1 for ports with USB 2.0 Link PM
enabled, which is not what we want.
This patch isn't necessary for kernels without USB 2.0 Link PM support,
even through the code to set the RWE bit has been in the kernel since
2.6.37 (commit 9777e3ce907d4cb5a513902a87ecd03b52499569 "USB: xHCI: bus
power management implementation" introduced it). Setting RWE when USB
2.0 Link PM is disabled for the port will have no effect on the xHCI
host controller behavior.
This patch should be backported to kernels as old as 3.2, that contain
support for USB 2.0 Link PM, starting with commit
9574323c39d1f8359a04843075d89c9f32d8b7e6 "xHCI: test USB2 software LPM".
Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/usb/host/xhci-hub.c | 26 --------------------------
1 file changed, 26 deletions(-)
diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 1d35459..eff8f26 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -1092,18 +1092,6 @@ int xhci_bus_suspend(struct usb_hcd *hcd)
t1 = xhci_port_state_to_neutral(t1);
if (t1 != t2)
xhci_writel(xhci, t2, port_array[port_index]);
-
- if (hcd->speed != HCD_USB3) {
- /* enable remote wake up for USB 2.0 */
- __le32 __iomem *addr;
- u32 tmp;
-
- /* Get the port power control register address. */
- addr = port_array[port_index] + PORTPMSC;
- tmp = xhci_readl(xhci, addr);
- tmp |= PORT_RWE;
- xhci_writel(xhci, tmp, addr);
- }
}
hcd->state = HC_STATE_SUSPENDED;
bus_state->next_statechange = jiffies + msecs_to_jiffies(10);
@@ -1182,20 +1170,6 @@ int xhci_bus_resume(struct usb_hcd *hcd)
xhci_ring_device(xhci, slot_id);
} else
xhci_writel(xhci, temp, port_array[port_index]);
-
- if (hcd->speed != HCD_USB3) {
- /* disable remote wake up for USB 2.0 */
- __le32 __iomem *addr;
- u32 tmp;
-
- /* Add one to the port status register address to get
- * the port power control register address.
- */
- addr = port_array[port_index] + PORTPMSC;
- tmp = xhci_readl(xhci, addr);
- tmp &= ~PORT_RWE;
- xhci_writel(xhci, tmp, addr);
- }
}
(void) xhci_readl(xhci, &xhci->op_regs->command);
--
1.8.3.3
--
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