mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-05 18:14:07 +08:00
5e99578685
It never made sense to keep these documents together; move each into its own file. Drop the section numbering on hsi.txt on its way to its own file. Suggested-by: Sebastian Reichel <sre@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
89 lines
3.1 KiB
ReStructuredText
89 lines
3.1 KiB
ReStructuredText
High Speed Synchronous Serial Interface (HSI)
|
|
=============================================
|
|
|
|
Introduction
|
|
---------------
|
|
|
|
High Speed Syncronous Interface (HSI) is a fullduplex, low latency protocol,
|
|
that is optimized for die-level interconnect between an Application Processor
|
|
and a Baseband chipset. It has been specified by the MIPI alliance in 2003 and
|
|
implemented by multiple vendors since then.
|
|
|
|
The HSI interface supports full duplex communication over multiple channels
|
|
(typically 8) and is capable of reaching speeds up to 200 Mbit/s.
|
|
|
|
The serial protocol uses two signals, DATA and FLAG as combined data and clock
|
|
signals and an additional READY signal for flow control. An additional WAKE
|
|
signal can be used to wakeup the chips from standby modes. The signals are
|
|
commonly prefixed by AC for signals going from the application die to the
|
|
cellular die and CA for signals going the other way around.
|
|
|
|
::
|
|
|
|
+------------+ +---------------+
|
|
| Cellular | | Application |
|
|
| Die | | Die |
|
|
| | - - - - - - CAWAKE - - - - - - >| |
|
|
| T|------------ CADATA ------------>|R |
|
|
| X|------------ CAFLAG ------------>|X |
|
|
| |<----------- ACREADY ------------| |
|
|
| | | |
|
|
| | | |
|
|
| |< - - - - - ACWAKE - - - - - - -| |
|
|
| R|<----------- ACDATA -------------|T |
|
|
| X|<----------- ACFLAG -------------|X |
|
|
| |------------ CAREADY ----------->| |
|
|
| | | |
|
|
| | | |
|
|
+------------+ +---------------+
|
|
|
|
HSI Subsystem in Linux
|
|
-------------------------
|
|
|
|
In the Linux kernel the hsi subsystem is supposed to be used for HSI devices.
|
|
The hsi subsystem contains drivers for hsi controllers including support for
|
|
multi-port controllers and provides a generic API for using the HSI ports.
|
|
|
|
It also contains HSI client drivers, which make use of the generic API to
|
|
implement a protocol used on the HSI interface. These client drivers can
|
|
use an arbitrary number of channels.
|
|
|
|
hsi-char Device
|
|
------------------
|
|
|
|
Each port automatically registers a generic client driver called hsi_char,
|
|
which provides a charecter device for userspace representing the HSI port.
|
|
It can be used to communicate via HSI from userspace. Userspace may
|
|
configure the hsi_char device using the following ioctl commands:
|
|
|
|
HSC_RESET
|
|
flush the HSI port
|
|
|
|
HSC_SET_PM
|
|
enable or disable the client.
|
|
|
|
HSC_SEND_BREAK
|
|
send break
|
|
|
|
HSC_SET_RX
|
|
set RX configuration
|
|
|
|
HSC_GET_RX
|
|
get RX configuration
|
|
|
|
HSC_SET_TX
|
|
set TX configuration
|
|
|
|
HSC_GET_TX
|
|
get TX configuration
|
|
|
|
The kernel HSI API
|
|
------------------
|
|
|
|
.. kernel-doc:: include/linux/hsi/hsi.h
|
|
:internal:
|
|
|
|
.. kernel-doc:: drivers/hsi/hsi_core.c
|
|
:export:
|
|
|