[PATCH] ehci: add think_time
This adds think_time to the usb_tt struct and sets it appropriately
(measured in ns); this can help us implement better split transaction
scheduling.
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 9f54e83..758c7f0 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -627,19 +627,33 @@
break;
}
+ /* Note 8 FS bit times == (8 bits / 12000000 bps) ~= 666ns */
switch (hub->descriptor->wHubCharacteristics & HUB_CHAR_TTTT) {
- case 0x00:
- if (hdev->descriptor.bDeviceProtocol != 0)
- dev_dbg(hub_dev, "TT requires at most 8 FS bit times\n");
+ case HUB_TTTT_8_BITS:
+ if (hdev->descriptor.bDeviceProtocol != 0) {
+ hub->tt.think_time = 666;
+ dev_dbg(hub_dev, "TT requires at most %d "
+ "FS bit times (%d ns)\n",
+ 8, hub->tt.think_time);
+ }
break;
- case 0x20:
- dev_dbg(hub_dev, "TT requires at most 16 FS bit times\n");
+ case HUB_TTTT_16_BITS:
+ hub->tt.think_time = 666 * 2;
+ dev_dbg(hub_dev, "TT requires at most %d "
+ "FS bit times (%d ns)\n",
+ 16, hub->tt.think_time);
break;
- case 0x40:
- dev_dbg(hub_dev, "TT requires at most 24 FS bit times\n");
+ case HUB_TTTT_24_BITS:
+ hub->tt.think_time = 666 * 3;
+ dev_dbg(hub_dev, "TT requires at most %d "
+ "FS bit times (%d ns)\n",
+ 24, hub->tt.think_time);
break;
- case 0x60:
- dev_dbg(hub_dev, "TT requires at most 32 FS bit times\n");
+ case HUB_TTTT_32_BITS:
+ hub->tt.think_time = 666 * 4;
+ dev_dbg(hub_dev, "TT requires at most %d "
+ "FS bit times (%d ns)\n",
+ 32, hub->tt.think_time);
break;
}
diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 53bf564..e7fa9b5 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -157,6 +157,12 @@
struct usb_device;
+/* Transaction Translator Think Times, in bits */
+#define HUB_TTTT_8_BITS 0x00
+#define HUB_TTTT_16_BITS 0x20
+#define HUB_TTTT_24_BITS 0x40
+#define HUB_TTTT_32_BITS 0x60
+
/*
* As of USB 2.0, full/low speed devices are segregated into trees.
* One type grows from USB 1.1 host controllers (OHCI, UHCI etc).
@@ -170,6 +176,7 @@
struct usb_tt {
struct usb_device *hub; /* upstream highspeed hub */
int multi; /* true means one TT per port */
+ unsigned think_time; /* think time in ns */
/* for control/bulk error recovery (CLEAR_TT_BUFFER) */
spinlock_t lock;
