USB: EHCI: EHCI 1.1 addendum: Enable Per-port change detect bits

This patch will enable Per-port event feature defined in EHCI 1.1
addendum. This feature addresses an issue where HCD is currently
required to read and parse PORTSC for all enabled root hub ports. With
this patch, the overhead will be reduced.

Signed-off-by: Alek Du <alek.du@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 17 insertions, 2 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index baf9b648bb1..8697ad19f31 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -584,6 +584,11 @@ static int ehci_init(struct usb_hcd *hcd)
         if (log2_irq_thresh < 0 || log2_irq_thresh > 6)
                 log2_irq_thresh = 0;
         temp = 1 << (16 + log2_irq_thresh);
+        if (HCC_PER_PORT_CHANGE_EVENT(hcc_params)) {
+                ehci->has_ppcd = 1;
+                ehci_dbg(ehci, "enable per-port change event\n");
+                temp |= CMD_PPCEE;
+        }
         if (HCC_CANPARK(hcc_params)) {
                 /* HW default park == 3, on hardware that supports it (like
                  * NVidia and ALI silicon), maximizes throughput on the async
@@ -782,6 +787,7 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
         /* remote wakeup [4.3.1] */
         if (status & STS_PCD) {
                 unsigned        i = HCS_N_PORTS (ehci->hcs_params);
+                u32             ppcd = 0;
 
                 /* kick root hub later */
                 pcd_status = status;
@@ -790,9 +796,18 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
                 if (!(cmd & CMD_RUN))
                         usb_hcd_resume_root_hub(hcd);
 
+                /* get per-port change detect bits */
+                if (ehci->has_ppcd)
+                        ppcd = status >> 16;
+
                 while (i--) {
-                        int pstatus = ehci_readl(ehci,
-                                                 &ehci->regs->port_status [i]);
+                        int pstatus;
+
+                        /* leverage per-port change bits feature */
+                        if (ehci->has_ppcd && !(ppcd & (1 << i)))
+                                continue;
+                        pstatus = ehci_readl(ehci,
+                                         &ehci->regs->port_status[i]);
 
                         if (pstatus & PORT_OWNER)
                                 continue;