Revision 23300f657594656e7ebac3130b43460ebc4381cc authored by Linus Torvalds on 19 February 2016, 16:40:05 UTC, committed by Linus Torvalds on 19 February 2016, 16:40:05 UTC
Pull arm64 fixes from Will Deacon: "Here are some more arm64 fixes for 4.5. This has mostly come from Yang Shi, who saw some issues under -rt that also affect mainline. The rest of it is pretty small, but still worth having. We've got an old issue outstanding with valid_user_regs which will likely wait until 4.6 (since it would really benefit from some time in -next) and another issue with kasan and idle which should be fixed next week. Apart from that, pretty quiet here (and still no sign of the THP issue reported on s390...) Summary: - Allow EFI stub to use strnlen(), which is required by recent libfdt - Avoid smp_processor_id() in preempt context during unwinding - Avoid false Kasan warnings during unwinding - Ensure early devices are picked up by the IOMMU DMA ops - Avoid rebuilding the kernel for the 'install' target - Run fixup handlers for alignment faults on userspace access" * tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: arm64: mm: allow the kernel to handle alignment faults on user accesses arm64: kbuild: make "make install" not depend on vmlinux arm64: dma-mapping: fix handling of devices registered before arch_initcall arm64/efi: Make strnlen() available to the EFI namespace arm/arm64: crypto: assure that ECB modes don't require an IV arm64: make irq_stack_ptr more robust arm64: debug: re-enable irqs before sending breakpoint SIGTRAP arm64: disable kasan when accessing frame->fp in unwind_frame
hsi.txt
HSI - High-speed Synchronous Serial Interface
1. 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 ----------->| |
| | | |
| | | |
+------------+ +---------------+
2. 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.
3. 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
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