USB: EHCI: create per-TT bandwidth tables

This patch continues the scheduling changes in ehci-hcd by adding a
table to store the bandwidth allocation below each TT.  This will
speed up the scheduling code, as it will no longer need to read
through the entire schedule to compute the bandwidth currently in use.

Properly speaking, the FS/LS budget calculations should be done in
terms of full-speed bytes per microframe, as described in the USB-2
spec.  However the driver currently uses microseconds per microframe,
and the scheduling code isn't robust enough at this point to change
over.  For the time being, we leave the calculations as they are.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 12504fbded56..e8f41c5e771b 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -61,6 +61,7 @@ struct ehci_stats {
 struct ehci_per_sched {
 	struct usb_device	*udev;		/* access to the TT */
 	struct usb_host_endpoint *ep;
+	struct list_head	ps_list;	/* node on ehci_tt's ps_list */
 	u16			tt_usecs;	/* time on the FS/LS bus */
 	u16			cs_mask;	/* C-mask and S-mask bytes */
 	u16			period;		/* actual period in frames */
@@ -256,6 +257,9 @@ struct ehci_hcd {			/* one per controller */
 #define EHCI_BANDWIDTH_FRAMES	(EHCI_BANDWIDTH_SIZE >> 3)
 	u8			bandwidth[EHCI_BANDWIDTH_SIZE];
 						/* us allocated per uframe */
+	u8			tt_budget[EHCI_BANDWIDTH_SIZE];
+						/* us budgeted per uframe */
+	struct list_head	tt_list;
 
 	/* platform-specific data -- must come last */
 	unsigned long		priv[0] __aligned(sizeof(s64));
@@ -595,6 +599,35 @@ struct ehci_fstn {
 
 /*-------------------------------------------------------------------------*/
 
+/*
+ * USB-2.0 Specification Sections 11.14 and 11.18
+ * Scheduling and budgeting split transactions using TTs
+ *
+ * A hub can have a single TT for all its ports, or multiple TTs (one for each
+ * port).  The bandwidth and budgeting information for the full/low-speed bus
+ * below each TT is self-contained and independent of the other TTs or the
+ * high-speed bus.
+ *
+ * "Bandwidth" refers to the number of microseconds on the FS/LS bus allocated
+ * to an interrupt or isochronous endpoint for each frame.  "Budget" refers to
+ * the best-case estimate of the number of full-speed bytes allocated to an
+ * endpoint for each microframe within an allocated frame.
+ *
+ * Removal of an endpoint invalidates a TT's budget.  Instead of trying to
+ * keep an up-to-date record, we recompute the budget when it is needed.
+ */
+
+struct ehci_tt {
+	u16			bandwidth[EHCI_BANDWIDTH_FRAMES];
+
+	struct list_head	tt_list;	/* List of all ehci_tt's */
+	struct list_head	ps_list;	/* Items using this TT */
+	struct usb_tt		*usb_tt;
+	int			tt_port;	/* TT port number */
+};
+
+/*-------------------------------------------------------------------------*/
+
 /* Prepare the PORTSC wakeup flags during controller suspend/resume */
 
 #define ehci_prepare_ports_for_controller_suspend(ehci, do_wakeup)	\