EHCI: force high-speed devices to run at full speed

This patch (as710) adds a sysfs class-device attribute file named
"companion" for EHCI controllers.  The file contains a list of port
numbers that are dedicated to the companion controller; by writing a
port number to the file the user can force a high-speed device
attached directly to the computer to run at full speed.  (As far as I
know it is not possible to do this for a device attached to an
external hub.)  A port is removed from the file by writing the
negative of its port number.

Several users have asked for this facility and it seems like a useful
thing to have.  Every now and then one runs across a device which
behaves much better at full speed than at high speed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 107 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c
index 076474d95dbf..3cfba69e0767 100644
--- a/drivers/usb/host/ehci-hub.c
+++ b/drivers/usb/host/ehci-hub.c
@@ -190,6 +190,103 @@ static int ehci_bus_resume (struct usb_hcd *hcd)
 
 /*-------------------------------------------------------------------------*/
 
+/* Display the ports dedicated to the companion controller */
+static ssize_t show_companion(struct class_device *class_dev, char *buf)
+{
+        struct ehci_hcd         *ehci;
+        int                     nports, index, n;
+        int                     count = PAGE_SIZE;
+        char                    *ptr = buf;
+
+        ehci = hcd_to_ehci(bus_to_hcd(class_get_devdata(class_dev)));
+        nports = HCS_N_PORTS(ehci->hcs_params);
+
+        for (index = 0; index < nports; ++index) {
+                if (test_bit(index, &ehci->companion_ports)) {
+                        n = scnprintf(ptr, count, "%d\n", index + 1);
+                        ptr += n;
+                        count -= n;
+                }
+        }
+        return ptr - buf;
+}
+
+/*
+ * Dedicate or undedicate a port to the companion controller.
+ * Syntax is "[-]portnum", where a leading '-' sign means
+ * return control of the port to the EHCI controller.
+ */
+static ssize_t store_companion(struct class_device *class_dev,
+                const char *buf, size_t count)
+{
+        struct ehci_hcd         *ehci;
+        int                     portnum, new_owner, try;
+        u32 __iomem             *status_reg;
+        u32                     port_status;
+
+        ehci = hcd_to_ehci(bus_to_hcd(class_get_devdata(class_dev)));
+        new_owner = PORT_OWNER;         /* Owned by companion */
+        if (sscanf(buf, "%d", &portnum) != 1)
+                return -EINVAL;
+        if (portnum < 0) {
+                portnum = - portnum;
+                new_owner = 0;          /* Owned by EHCI */
+        }
+        if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
+                return -ENOENT;
+        status_reg = &ehci->regs->port_status[--portnum];
+        if (new_owner)
+                set_bit(portnum, &ehci->companion_ports);
+        else
+                clear_bit(portnum, &ehci->companion_ports);
+
+        /*
+         * The controller won't set the OWNER bit if the port is
+         * enabled, so this loop will sometimes require at least two
+         * iterations: one to disable the port and one to set OWNER.
+         */
+
+        for (try = 4; try > 0; --try) {
+                spin_lock_irq(&ehci->lock);
+                port_status = ehci_readl(ehci, status_reg);
+                if ((port_status & PORT_OWNER) == new_owner
+                                || (port_status & (PORT_OWNER | PORT_CONNECT))
+                                        == 0)
+                        try = 0;
+                else {
+                        port_status ^= PORT_OWNER;
+                        port_status &= ~(PORT_PE | PORT_RWC_BITS);
+                        ehci_writel(ehci, port_status, status_reg);
+                }
+                spin_unlock_irq(&ehci->lock);
+                if (try > 1)
+                        msleep(5);
+        }
+        return count;
+}
+static CLASS_DEVICE_ATTR(companion, 0644, show_companion, store_companion);
+
+static inline void create_companion_file(struct ehci_hcd *ehci)
+{
+        int     i;
+
+        /* with integrated TT there is no companion! */
+        if (!ehci_is_TDI(ehci))
+                i = class_device_create_file(ehci_to_hcd(ehci)->self.class_dev,
+                                &class_device_attr_companion);
+}
+
+static inline void remove_companion_file(struct ehci_hcd *ehci)
+{
+        /* with integrated TT there is no companion! */
+        if (!ehci_is_TDI(ehci))
+                class_device_remove_file(ehci_to_hcd(ehci)->self.class_dev,
+                                &class_device_attr_companion);
+}
+
+
+/*-------------------------------------------------------------------------*/
+
 static int check_reset_complete (
         struct ehci_hcd *ehci,
         int             index,
@@ -504,6 +601,16 @@ static int ehci_hub_control (
                                         ehci_readl(ehci, status_reg));
                 }
 
+                /* transfer dedicated ports to the companion hc */
+                if ((temp & PORT_CONNECT) &&
+                                test_bit(wIndex, &ehci->companion_ports)) {
+                        temp &= ~PORT_RWC_BITS;
+                        temp |= PORT_OWNER;
+                        ehci_writel(ehci, temp, status_reg);
+                        ehci_dbg(ehci, "port %d --> companion\n", wIndex + 1);
+                        temp = ehci_readl(ehci, status_reg);
+                }
+
                 /*
                  * Even if OWNER is set, there's no harm letting khubd
                  * see the wPortStatus values (they should all be 0 except