mirror of
https://github.com/hardkernel/linux.git
synced 2026-04-06 05:03:13 +09:00
d6dc21d7de
According to "TX/RX Data FIFO Sizes and TX/RX Threshold Control Register Settings" section in the DWC SuperSpeed USB 3.0 Controller User Guide, for large latency systems, it may cause unnecessary performance reduction, and having large TX/RX FIFOs alone is not sufficient, to solve this issue, the controller provides a packet threshold feature in the host mode. For example, on rk3399 platforms, if we set aclk_perilp to 100 MHz, the system usb bus latency is larger than 2.2 microseconds to access a 1024-byte packet, to avoid underrun and overrun during the burst, threshold and burst size control must be set through GTXTHRCFG and GRXTHRCFG registers. On rk3399 platforms, only a 4-packet TX FIFO and 3-packet RX FIFO is implemented due to area constraints, so we can program the USB Maximum TX Burst Size to 13 and the USB Transmit Packet Count to 4 to avoid TX FIFO underrun during an OUT burst. Similarly, set the USB Maximum TX Burst Size to 10 and the USB Transmit Packet Count to 2 to avoid RX FIFO overrrun. To enable the threshold control, add "snps,gtx-threshold-cfg = <4>, <13>" in dts dwc3 node for Tx, add "snps,grx-threshold-cfg = <2>, <10>" in dts dwc3 node for Rx. Change-Id: I7535fe72e6527544a20c5921440b4888e1bada22 Signed-off-by: William Wu <william.wu@rock-chips.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.