UHCI: Eliminate asynchronous skeleton Queue Headers

This patch (as856) attempts to improve the performance of uhci-hcd by
removing the asynchronous skeleton Queue Headers.  They don't contain
any useful information but the controller has to read through them at
least once every millisecond, incurring a non-zero DMA overhead.

Now all the asynchronous queues are combined, along with the period-1
interrupt queue, into a single list with a single skeleton QH.  The
start of the low-speed control, full-speed control, and bulk sublists
is determined by linear search.  Since there should rarely be more
than a couple of QHs in the list, the searches should incur a much
smaller total load than keeping the skeleton QHs.

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

1 files changed, 28 insertions, 22 deletions

diff --git a/drivers/usb/host/uhci-debug.c b/drivers/usb/host/uhci-debug.c
index a0677133577b..8d24d3dc0a61 100644
--- a/drivers/usb/host/uhci-debug.c
+++ b/drivers/usb/host/uhci-debug.c
@@ -220,16 +220,6 @@ static int uhci_show_qh(struct uhci_qh *qh, char *buf, int len, int space)
         return out - buf;
 }
 
-static const char * const qh_names[] = {
-  "skel_unlink_qh", "skel_iso_qh",
-  "skel_int128_qh", "skel_int64_qh",
-  "skel_int32_qh", "skel_int16_qh",
-  "skel_int8_qh", "skel_int4_qh",
-  "skel_int2_qh", "skel_int1_qh",
-  "skel_ls_control_qh", "skel_fs_control_qh",
-  "skel_bulk_qh", "skel_term_qh"
-};
-
 static int uhci_show_sc(int port, unsigned short status, char *buf, int len)
 {
         char *out = buf;
@@ -352,6 +342,12 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
         struct uhci_td *td;
         struct list_head *tmp, *head;
         int nframes, nerrs;
+        __le32 link;
+
+        static const char * const qh_names[] = {
+                "unlink", "iso", "int128", "int64", "int32", "int16",
+                "int8", "int4", "int2", "async", "term"
+        };
 
         out += uhci_show_root_hub_state(uhci, out, len - (out - buf));
         out += sprintf(out, "HC status\n");
@@ -374,7 +370,7 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
         nframes = 10;
         nerrs = 0;
         for (i = 0; i < UHCI_NUMFRAMES; ++i) {
-                __le32 link, qh_dma;
+                __le32 qh_dma;
 
                 j = 0;
                 td = uhci->frame_cpu[i];
@@ -430,23 +426,21 @@ check_link:
 
         for (i = 0; i < UHCI_NUM_SKELQH; ++i) {
                 int cnt = 0;
+                __le32 fsbr_link = 0;
 
                 qh = uhci->skelqh[i];
-                out += sprintf(out, "- %s\n", qh_names[i]); \
+                out += sprintf(out, "- skel_%s_qh\n", qh_names[i]); \
                 out += uhci_show_qh(qh, out, len - (out - buf), 4);
 
                 /* Last QH is the Terminating QH, it's different */
-                if (i == UHCI_NUM_SKELQH - 1) {
-                        if (qh->link != UHCI_PTR_TERM)
-                                out += sprintf(out, "    bandwidth reclamation on!\n");
-
+                if (i == SKEL_TERM) {
                         if (qh_element(qh) != LINK_TO_TD(uhci->term_td))
                                 out += sprintf(out, "    skel_term_qh element is not set to term_td!\n");
-
+                        if (link == LINK_TO_QH(uhci->skel_term_qh))
+                                goto check_qh_link;
                         continue;
                 }
 
-                j = (i < 9) ? 9 : i+1;          /* Next skeleton */
                 head = &qh->node;
                 tmp = head->next;
 
@@ -456,14 +450,26 @@ check_link:
                         if (++cnt <= 10)
                                 out += uhci_show_qh(qh, out,
                                                 len - (out - buf), 4);
+                        if (!fsbr_link && qh->skel >= SKEL_FSBR)
+                                fsbr_link = LINK_TO_QH(qh);
                 }
                 if ((cnt -= 10) > 0)
                         out += sprintf(out, "    Skipped %d QHs\n", cnt);
 
-                if (i > 1 && i < UHCI_NUM_SKELQH - 1) {
-                        if (qh->link != LINK_TO_QH(uhci->skelqh[j]))
-                                out += sprintf(out, "    last QH not linked to next skeleton!\n");
-                }
+                link = UHCI_PTR_TERM;
+                if (i <= SKEL_ISO)
+                        ;
+                else if (i < SKEL_ASYNC)
+                        link = LINK_TO_QH(uhci->skel_async_qh);
+                else if (!uhci->fsbr_is_on)
+                        ;
+                else if (fsbr_link)
+                        link = fsbr_link;
+                else
+                        link = LINK_TO_QH(uhci->skel_term_qh);
+check_qh_link:
+                if (qh->link != link)
+                        out += sprintf(out, "    last QH not linked to next skeleton!\n");
         }
 
         return out - buf;