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  1. 13 8月, 2013 1 次提交
    • M
      USB: HCD: support giveback of URB in tasklet context · 94dfd7ed
      由 Ming Lei 提交于 
      This patch implements the mechanism of giveback of URB in
tasklet context, so that hardware interrupt handling time for
usb host controller can be saved much, and HCD interrupt handling
can be simplified.

Motivations:

1), on some arch(such as ARM), DMA mapping/unmapping is a bit
time-consuming, for example: when accessing usb mass storage
via EHCI on pandaboard, the common length of transfer buffer is 120KB,
the time consumed on DMA unmapping may reach hundreds of microseconds;
even on A15 based box, the time is still about scores of microseconds

2), on some arch, reading DMA coherent memoery is very time-consuming,
the most common example is usb video class driver[1]

3), driver's complete() callback may do much things which is driver
specific, so the time is consumed unnecessarily in hardware irq context.

4), running driver's complete() callback in hardware irq context causes
that host controller driver has to release its lock in interrupt handler,
so reacquiring the lock after return may busy wait a while and increase
interrupt handling time. More seriously, releasing the HCD lock makes
HCD becoming quite complicated to deal with introduced races.

So the patch proposes to run giveback of URB in tasklet context, then
time consumed in HCD irq handling doesn't depend on drivers' complete and
DMA mapping/unmapping any more, also we can simplify HCD since the HCD
lock isn't needed to be released during irq handling.

The patch should be reasonable and doable:

1), for drivers, they don't care if the complete() is called in hard irq
context or softirq context

2), the biggest change is the situation in which usb_submit_urb() is called
in complete() callback, so the introduced tasklet schedule delay might be a
con, but it shouldn't be a big deal:

	- control/bulk asynchronous transfer isn't sensitive to schedule
	  delay

	- the patch schedules giveback of periodic URBs using
	  tasklet_hi_schedule, so the introduced delay should be very
	  small

	- for ISOC transfer, generally, drivers submit several URBs
	  concurrently to avoid interrupt delay, so it is OK with the
	  little schedule delay.

	- for interrupt transfer, generally, drivers only submit one URB
	  at the same time, but interrupt transfer is often used in event
	  report, polling, ... situations, and a little delay should be OK.

Considered that HCDs may optimize on submitting URB in complete(), the
patch may cause the optimization not working, so introduces one flag to mark
if the HCD supports to run giveback URB in tasklet context. When all HCDs
are ready, the flag can be removed.

[1], http://marc.info/?t=136438111600010&r=1&w=2

Cc: Oliver Neukum <oliver@neukum.org>
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      94dfd7ed
  3. 03 8月, 2013 1 次提交
  5. 02 8月, 2013 3 次提交
    • B
      USB: ohci-at91: add usb_clk for transition to common clk framework · 6b0a1cf7
      由 Boris BREZILLON 提交于 
      The AT91 PMC (Power Management Controller) provides an USB clock used by
USB Full Speed host (ohci) and USB Full Speed device (udc).
The usb drivers (ohci and udc) must configure this clock to 48Mhz.
This configuration was formely done in mach-at91/clock.c, but this
implementation will be removed when moving to common clk framework.

This patch adds support for usb clock retrieval and configuration, and is
backward compatible with the current at91 clk implementation (if usb clk
is not found, it does not configure/enable it).

Changes since v1:
 - use IS_ENABLED(CONFIG_COMMON_CLK) to isolate new at91 clk support
Signed-off-by: NBoris BREZILLON <b.brezillon@overkiz.com>
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      6b0a1cf7
    • A
      USB: EHCI: don't depend on hardware for tracking port resets and resumes · 6753f4cf
      由 Alan Stern 提交于 
      In theory, an EHCI controller can turn off the PORT_RESUME or
PORT_RESET bits in a port status register all by itself (and some
controllers actually do this).  We shouldn't depend on these bits
being set correctly.

This patch rearranges the code in ehci-hcd that handles completion of
port resets and resumes.  We guarantee that ehci->reset_done[portnum]
is nonzero if a reset or resume is in progress, and that the portnum
bit is set in ehci->resuming_ports if the operation is a resume.  (To
help enforce this guarantee, the patch prevents suspended ports from
being reset.)  Therefore it's not necessary to look at the port status
bits to learn what's going on.

The patch looks bigger than it really is, because it changes the
indentation level of a sizeable region of code.  Most of what it
actually does is interchange some tests.  The only functional changes
are testing reset_done and resuming_ports rather than PORT_RESUME and
PORT_RESET, removing a now-unnecessary check for spontaneous
resets of the PORT_RESUME and PORT_RESET bits, and preventing a
suspended or resuming port from being reset.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      6753f4cf
    • A
      USB: EHCI: keep better track of resuming ports · 3a20446f
      由 Alan Stern 提交于 
      The ehci-hcd driver isn't as careful as it should be about the way it
uses ehci->resuming_ports.  One of the omissions was fixed recently by
commit 47a64a13 (USB: EHCI: Fix resume signalling on remote
wakeup), but there are other places that need attention:

	When a port's suspend feature is explicitly cleared, the
	corresponding bit in resuming_ports should be set and the core
	should be notified about the port resume.

	We don't need to clear a resuming_ports bit when a reset
	completes.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      3a20446f
  7. 01 8月, 2013 9 次提交
  9. 30 7月, 2013 5 次提交
  11. 29 7月, 2013 4 次提交
  13. 27 7月, 2013 10 次提交
  15. 26 7月, 2013 7 次提交