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In (usb: dwc2: reset dwc2 core before dwc2_get_hwparams()) we added an extra reset to the probe path for the dwc2 USB controllers. This allowed proper detection of parameters even if the firmware had already used the USB part. Unfortunately, this extra reset is quite slow and is affecting boot speed. We can avoid the double-reset by skipping the extra reset that would happen just after the one we added. Logic that explains why this is safe: * As of the CL mentioned above, we now always call dwc2_core_reset() in dwc2_driver_probe() before dwc2_hcd_init(). * The only caller of dwc2_hcd_init() is dwc2_driver_probe(), so we're guaranteed that dwc2_core_reset() was called before dwc2_hdc_init(). * dwc2_hdc_init() is the only caller that passes an irq other than -1 to dwc2_core_init(). Thus if dwc2_core_init() is called with an irq other than -1 we're guaranteed that dwc2_core_reset was called before dwc2_core_init(). ...this allows us to remove the dwc2_core_reset() in dwc2_core_init() if irq is not < 0. Note that since "irq" wasn't used in the function dwc2_core_init() anyway and since select_phy was always set at exactly the same times we could avoid the reset, we remove "irq" and rename "select_phy" to "initial_setup" and adjust the callers accordingly. Signed-off-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: John Youn <johnyoun@synopsys.com> Signed-off-by: Felipe Balbi <balbi@ti.com>
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.