Revision 474095e46cd14421821da3201a9fd6a4c070996b authored by Linus Torvalds on 24 April 2015, 16:28:01 UTC, committed by Linus Torvalds on 24 April 2015, 16:28:01 UTC
Pull md updates from Neil Brown: "More updates that usual this time. A few have performance impacts which hould mostly be positive, but RAID5 (in particular) can be very work-load ensitive... We'll have to wait and see. Highlights: - "experimental" code for managing md/raid1 across a cluster using DLM. Code is not ready for general use and triggers a WARNING if used. However it is looking good and mostly done and having in mainline will help co-ordinate development. - RAID5/6 can now batch multiple (4K wide) stripe_heads so as to handle a full (chunk wide) stripe as a single unit. - RAID6 can now perform read-modify-write cycles which should help performance on larger arrays: 6 or more devices. - RAID5/6 stripe cache now grows and shrinks dynamically. The value set is used as a minimum. - Resync is now allowed to go a little faster than the 'mininum' when there is competing IO. How much faster depends on the speed of the devices, so the effective minimum should scale with device speed to some extent" * tag 'md/4.1' of git://neil.brown.name/md: (58 commits) md/raid5: don't do chunk aligned read on degraded array. md/raid5: allow the stripe_cache to grow and shrink. md/raid5: change ->inactive_blocked to a bit-flag. md/raid5: move max_nr_stripes management into grow_one_stripe and drop_one_stripe md/raid5: pass gfp_t arg to grow_one_stripe() md/raid5: introduce configuration option rmw_level md/raid5: activate raid6 rmw feature md/raid6 algorithms: xor_syndrome() for SSE2 md/raid6 algorithms: xor_syndrome() for generic int md/raid6 algorithms: improve test program md/raid6 algorithms: delta syndrome functions raid5: handle expansion/resync case with stripe batching raid5: handle io error of batch list RAID5: batch adjacent full stripe write raid5: track overwrite disk count raid5: add a new flag to track if a stripe can be batched raid5: use flex_array for scribble data md raid0: access mddev->queue (request queue member) conditionally because it is not set when accessed from dm-raid md: allow resync to go faster when there is competing IO. md: remove 'go_faster' option from ->sync_request() ...
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
![swh spinner](/static/img/swh-spinner.gif)
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