diff options
Diffstat (limited to 'cdc-acm.patch')
| -rw-r--r-- | cdc-acm.patch | 115 |
1 files changed, 0 insertions, 115 deletions
diff --git a/cdc-acm.patch b/cdc-acm.patch deleted file mode 100644 index 80573ccb2ea33e..00000000000000 --- a/cdc-acm.patch +++ /dev/null @@ -1,115 +0,0 @@ -From foo@baz Fri Jun 7 11:21:41 PDT 2013 -Date: Fri, 07 Jun 2013 11:21:41 -0700 -To: Greg KH <gregkh@linuxfoundation.org> -From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> -Subject: [PATCH] USB: cdc-acm: remove unneeded spinlock call on write path - -When writing data we were: - lock - do some work - unlock - call function - lock - do some work - unlock - return - return - -It turns out, that "function" was only ever called in the one place, so -instead of locking/unlocking for no good reason, just inline the -function and only grab the lock once. - -This has sped up the pathological case of sending 1 byte packets to a -loop-back cdc-acm device from 49600 bytes per second to 50100 bytes a -second on my workstation. A tiny increase yes, but noticable, and now -the spinlock isn't the hottest thing on the perf graph anymore. Yes, we -are still waiting for the hardware for the most part, but getting rid of -a spinlock_irq_save() call for every packet is still a good thing. - -And we end up deleting lines of code, always a win overall. - -This was found by using a Teensy 3.0 device and the test program and -firmware located at: - http://www.pjrc.com/teensy/benchmark_usb_serial_receive.html - -Reported-by: Paul Stoffregen <paul@pjrc.com> -Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> - ---- - drivers/usb/class/cdc-acm.c | 52 ++++++++++++++++---------------------------- - 1 file changed, 19 insertions(+), 33 deletions(-) - ---- a/drivers/usb/class/cdc-acm.c -+++ b/drivers/usb/class/cdc-acm.c -@@ -216,38 +216,6 @@ static int acm_start_wb(struct acm *acm, - return rc; - } - --static int acm_write_start(struct acm *acm, int wbn) --{ -- unsigned long flags; -- struct acm_wb *wb = &acm->wb[wbn]; -- int rc; -- -- spin_lock_irqsave(&acm->write_lock, flags); -- if (!acm->dev) { -- wb->use = 0; -- spin_unlock_irqrestore(&acm->write_lock, flags); -- return -ENODEV; -- } -- -- dev_vdbg(&acm->data->dev, "%s - susp_count %d\n", __func__, -- acm->susp_count); -- usb_autopm_get_interface_async(acm->control); -- if (acm->susp_count) { -- if (!acm->delayed_wb) -- acm->delayed_wb = wb; -- else -- usb_autopm_put_interface_async(acm->control); -- spin_unlock_irqrestore(&acm->write_lock, flags); -- return 0; /* A white lie */ -- } -- usb_mark_last_busy(acm->dev); -- -- rc = acm_start_wb(acm, wb); -- spin_unlock_irqrestore(&acm->write_lock, flags); -- -- return rc; -- --} - /* - * attributes exported through sysfs - */ -@@ -653,13 +621,31 @@ static int acm_tty_write(struct tty_stru - } - wb = &acm->wb[wbn]; - -+ if (!acm->dev) { -+ wb->use = 0; -+ spin_unlock_irqrestore(&acm->write_lock, flags); -+ return -ENODEV; -+ } -+ - count = (count > acm->writesize) ? acm->writesize : count; - dev_vdbg(&acm->data->dev, "%s - write %d\n", __func__, count); - memcpy(wb->buf, buf, count); - wb->len = count; -+ -+ usb_autopm_get_interface_async(acm->control); -+ if (acm->susp_count) { -+ if (!acm->delayed_wb) -+ acm->delayed_wb = wb; -+ else -+ usb_autopm_put_interface_async(acm->control); -+ spin_unlock_irqrestore(&acm->write_lock, flags); -+ return count; /* A white lie */ -+ } -+ usb_mark_last_busy(acm->dev); -+ -+ stat = acm_start_wb(acm, wb); - spin_unlock_irqrestore(&acm->write_lock, flags); - -- stat = acm_write_start(acm, wbn); - if (stat < 0) - return stat; - return count; |