linux/drivers/usb
Terin Stock 6ed30a7d8e usb: dwc2: host: use hrtimer for NAK retries
Modify the wait delay utilize the high resolution timer API to allow for
more precisely scheduled callbacks.

A previous commit added a 1ms retry delay after multiple consecutive
NAKed transactions using jiffies. On systems with a low timer interrupt
frequency, this delay may be significantly longer than specified,
resulting in misbehavior with some USB devices.

This scenario was reached on a Raspberry Pi 3B with a Macally FDD-USB
floppy drive (identified as 0424:0fdc Standard Microsystems Corp.
Floppy, based on the USB97CFDC USB FDC). With the relay delay, the drive
would be unable to mount a disk, replying with NAKs until the device was
reset.

Using ktime, the delta between starting the timer (in dwc2_hcd_qh_add)
and the callback function can be determined. With the original delay
implementation, this value was consistently approximately 12ms. (output
in us).

    <idle>-0     [000] ..s.  1600.559974: dwc2_wait_timer_fn: wait_timer delta: 11976
    <idle>-0     [000] ..s.  1600.571974: dwc2_wait_timer_fn: wait_timer delta: 11977
    <idle>-0     [000] ..s.  1600.583974: dwc2_wait_timer_fn: wait_timer delta: 11976
    <idle>-0     [000] ..s.  1600.595974: dwc2_wait_timer_fn: wait_timer delta: 11977

After converting the relay delay to using a higher resolution timer, the
delay was much closer to 1ms.

    <idle>-0     [000] d.h.  1956.553017: dwc2_wait_timer_fn: wait_timer delta: 1002
    <idle>-0     [000] d.h.  1956.554114: dwc2_wait_timer_fn: wait_timer delta: 1002
    <idle>-0     [000] d.h.  1957.542660: dwc2_wait_timer_fn: wait_timer delta: 1004
    <idle>-0     [000] d.h.  1957.543701: dwc2_wait_timer_fn: wait_timer delta: 1002

The floppy drive operates properly with delays up to approximately 5ms,
and sends NAKs for any delays that are longer.

Fixes: 38d2b5fb75 ("usb: dwc2: host: Don't retry NAKed transactions right away")
Cc: <stable@vger.kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Terin Stock <terin@terinstock.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
2018-12-05 11:13:14 +02:00
..
atm USB: atm: fix up some remaining DEVICE_ATTR() usage 2018-01-24 08:49:52 +01:00
c67x00 USB: add SPDX identifiers to all remaining Makefiles 2017-11-07 15:53:48 +01:00
chipidea usb: chipidea: Fix otg event handler 2018-09-20 17:04:22 +08:00
class usb: cdc-acm: add entry for Hiro (Conexant) modem 2018-11-20 12:12:06 +01:00
common usb: roles: Take care of driver module reference counting 2018-09-20 13:20:24 +02:00
core usb: core: Fix hub port connection events lost 2018-11-14 14:28:26 -08:00
dwc2 usb: dwc2: host: use hrtimer for NAK retries 2018-12-05 11:13:14 +02:00
dwc3 usb: dwc3: Correct the logic for checking TRB full in __dwc3_prepare_one_trb() 2018-12-05 10:44:55 +02:00
early mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
gadget usb: gadget: f_fs: Allow scatter-gather buffers 2018-11-26 09:06:32 +02:00
host usb: xhci: Prevent bus suspend if a port connect change or polling state is detected 2018-11-15 09:17:40 -08:00
image USB/PHY patches for 4.15-rc1 2017-11-13 21:14:07 -08:00
isp1760 usb: isp1760: remove redundant variable 'selector' 2018-07-13 15:41:56 +02:00
misc USB: misc: appledisplay: add 20" Apple Cinema Display 2018-11-07 13:23:18 +01:00
mon USB: mon: use ktime_get_real_ts64 instead of getnstimeofday64 2018-06-25 21:58:26 +08:00
mtu3 usb: mtu3: clear SOFTCONN when clear USB3_EN if work as HS mode 2018-12-05 11:12:28 +02:00
musb usb: musb: dsps: do not disable CPPI41 irq in driver teardown 2018-09-20 12:40:14 +02:00
phy usb: phy: ab8500: silence some uninitialized variable warnings 2018-10-18 19:44:39 +02:00
renesas_usbhs usb: renesas_usbhs: add support for R-Car E3 2018-10-02 10:48:08 +03:00
roles usb: roles: intel_xhci: Fix Unbalanced pm_runtime_enable 2018-10-09 16:13:42 +02:00
serial USB/PHY patches for 4.20-rc1 2018-10-26 08:14:13 -07:00
storage USB: STORAGE: ISD200 Fixed coding style issue "space required in for loop" 2018-09-20 15:10:29 +02:00
typec usb: typec: ucsi: add support for Cypress CCGx 2018-11-09 18:49:59 +01:00
usbip Merge branch 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 19:58:52 -07:00
wusbcore USB/PHY patches for 4.20-rc1 2018-10-26 08:14:13 -07:00
Kconfig usb: select USB_COMMON for usb role switch config 2018-04-22 15:23:37 +02:00
Makefile usb: roles: Add Intel xHCI USB role switch driver 2018-03-22 13:49:27 +01:00
README
usb-skeleton.c usb: usb-skeleton: use irqsave() in USB's complete callback 2018-06-28 19:36:06 +09:00

To understand all the Linux-USB framework, you'll use these resources:

    * This source code.  This is necessarily an evolving work, and
      includes kerneldoc that should help you get a current overview.
      ("make pdfdocs", and then look at "usb.pdf" for host side and
      "gadget.pdf" for peripheral side.)  Also, Documentation/usb has
      more information.

    * The USB 2.0 specification (from www.usb.org), with supplements
      such as those for USB OTG and the various device classes.
      The USB specification has a good overview chapter, and USB
      peripherals conform to the widely known "Chapter 9".

    * Chip specifications for USB controllers.  Examples include
      host controllers (on PCs, servers, and more); peripheral
      controllers (in devices with Linux firmware, like printers or
      cell phones); and hard-wired peripherals like Ethernet adapters.

    * Specifications for other protocols implemented by USB peripheral
      functions.  Some are vendor-specific; others are vendor-neutral
      but just standardized outside of the www.usb.org team.

Here is a list of what each subdirectory here is, and what is contained in
them.

core/		- This is for the core USB host code, including the
		  usbfs files and the hub class driver ("hub_wq").

host/		- This is for USB host controller drivers.  This
		  includes UHCI, OHCI, EHCI, and others that might
		  be used with more specialized "embedded" systems.

gadget/		- This is for USB peripheral controller drivers and
		  the various gadget drivers which talk to them.


Individual USB driver directories.  A new driver should be added to the
first subdirectory in the list below that it fits into.

image/		- This is for still image drivers, like scanners or
		  digital cameras.
../input/	- This is for any driver that uses the input subsystem,
		  like keyboard, mice, touchscreens, tablets, etc.
../media/	- This is for multimedia drivers, like video cameras,
		  radios, and any other drivers that talk to the v4l
		  subsystem.
../net/		- This is for network drivers.
serial/		- This is for USB to serial drivers.
storage/	- This is for USB mass-storage drivers.
class/		- This is for all USB device drivers that do not fit
		  into any of the above categories, and work for a range
		  of USB Class specified devices. 
misc/		- This is for all USB device drivers that do not fit
		  into any of the above categories.