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Subject[PATCH] Slight optimisation of the uhci-hcd init code
Hello,

While trying to understand why starting usb on my laptop made the bus master
activity full I came accross a strange code in uhci-hcd: a seven level nested
"if". The same thing can be achieved with a simgle ffz(). The attached patch
should give to the code a bit better looking, on my x86 it even saves 96 bytes,
cool ;-)

hoping you like it,
Eric Piel


PS: still, I'm not sure it's normal to see ffffffff as "bus master activity" in
/proc/acpi/processor/CPU0/power as soon as uhci-hcd is loaded. In particular, it
prevents the processor to go to C3 state. Could you give me your pint of view?--- drivers/usb/host/uhci-hcd.c.orig 2004-02-08 12:30:23.730934744 +0100
+++ drivers/usb/host/uhci-hcd.c 2004-02-08 13:12:11.723661896 +0100
@@ -52,6 +52,7 @@
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/system.h>
+#include <asm/bitops.h>

#include "../core/hcd.h"
#include "uhci-hcd.h"
@@ -2213,10 +2214,11 @@
{
struct uhci_hcd *uhci = hcd_to_uhci(hcd);
int retval = -EBUSY;
- int i, port;
+ int port;
unsigned io_size;
dma_addr_t dma_handle;
struct usb_device *udev;
+ unsigned long i;
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *ent;
#endif
@@ -2321,7 +2323,7 @@
for (i = 0; i < UHCI_NUM_SKELQH; i++) {
uhci->skelqh[i] = uhci_alloc_qh(uhci, udev);
if (!uhci->skelqh[i]) {
- err("unable to allocate QH %d", i);
+ err("unable to allocate QH %lu", i);
goto err_alloc_skelqh;
}
}
@@ -2360,28 +2362,8 @@
* us a reasonable dynamic range for irq latencies.
*/
for (i = 0; i < UHCI_NUMFRAMES; i++) {
- int irq = 0;
-
- if (i & 1) {
- irq++;
- if (i & 2) {
- irq++;
- if (i & 4) {
- irq++;
- if (i & 8) {
- irq++;
- if (i & 16) {
- irq++;
- if (i & 32) {
- irq++;
- if (i & 64)
- irq++;
- }
- }
- }
- }
- }
- }
+ unsigned long irq;
+ irq = ffz(i & ((1<<7) - 1));

/* Only place we don't use the frame list routines */
uhci->fl->frame[i] = cpu_to_le32(uhci->skelqh[7 - irq]->dma_handle);
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