Lines Matching refs:SPI
2 Overview of Linux kernel SPI support
7 What is SPI?
9 The "Serial Peripheral Interface" (SPI) is a synchronous four wire serial
12 standardization body. SPI uses a master/slave configuration.
22 SPI masters use a fourth "chip select" line to activate a given SPI slave
24 in parallel. All SPI slaves support chipselects; they are usually active
29 SPI slave functions are usually not interoperable between vendors
30 (except for commodities like SPI memory chips).
32 - SPI may be used for request/response style device protocols, as with
44 - Sometimes SPI is used to daisy-chain devices, like shift registers.
46 In the same way, SPI slaves will only rarely support any kind of automatic
48 a given SPI master will normally be set up manually, with configuration
51 SPI is only one of the names used by such four-wire protocols, and
53 half-duplex SPI, for request/response protocols), SSP ("Synchronous
59 some SPI chips have this signal mode as a strapping option. These
60 can be accessed using the same programming interface as SPI, but of
65 Microcontrollers often support both master and slave sides of the SPI
67 sides of SPI interactions.
72 Linux developers using SPI are probably writing device drivers for embedded
73 systems boards. SPI is used to control external chips, and it is also a
76 support only SPI.) Some PC hardware uses SPI flash for BIOS code.
78 SPI slave chips range from digital/analog converters used for analog
82 Most systems using SPI will integrate a few devices on a mainboard.
83 Some provide SPI links on expansion connectors; in cases where no
84 dedicated SPI controller exists, GPIO pins can be used to create a
85 low speed "bitbanging" adapter. Very few systems will "hotplug" an SPI
86 controller; the reasons to use SPI focus on low cost and simple operation,
91 interfaces with SPI modes. Given SPI support, they could use MMC or SD
95 I'm confused. What are these four SPI "clock modes"?
112 Chip specs won't always say "uses SPI mode X" in as many words,
115 In the SPI mode number, CPOL is the high order bit and CPHA is the
118 trailing clock edge (CPHA=1), that's SPI mode 1.
135 SPI requests always go into I/O queues. Requests for a given SPI device
141 There are two types of SPI driver, here called:
152 other side of an SPI link.
155 data to filesystems stored on SPI flash like DataFlash; and others might
163 There is a minimal core of SPI programming interfaces, focussing on
165 device tables provided by board specific initialization code. SPI
168 /sys/devices/.../CTLR ... physical node for a given SPI controller
182 a logical node which could hold class related state for the SPI
184 physical SPI bus segment, with SCLK, MOSI, and MISO.
187 slave device for an SPI slave controller.
188 Writing the driver name of an SPI slave handler to this file
195 a logical node which could hold class related state for the SPI
197 device is present here, possible sharing the physical SPI bus
198 segment with other SPI slave devices.
206 How does board-specific init code declare SPI devices?
208 Linux needs several kinds of information to properly configure SPI devices.
215 The first kind of information is a list of what SPI controllers exist.
221 Platforms will often abstract the "register SPI controller" operation,
225 SPI-capable controllers, and only the ones actually usable on a given
240 /* this board only uses SPI controller #2 */
272 same SOC controller is used. For example, on one board SPI might use
273 an external clock, where another derives the SPI clock from current
279 The second kind of information is a list of what SPI slave devices exist
284 listing the SPI devices on each board. (This would typically be only a
306 several types. This example shows generic constraints like the fastest SPI
321 Then your board initialization code would register that table with the SPI
322 infrastructure, so that it's available later when the SPI master controller
333 certainly includes SPI devices hooked up through the card connectors!
340 example is the potential need to hotplug SPI devices and/or controllers.
347 When Linux includes support for MMC/SD/SDIO/DataFlash cards through SPI, those
352 How do I write an "SPI Protocol Driver"?
354 Most SPI drivers are currently kernel drivers, but there's also support
357 SPI protocol drivers somewhat resemble platform device drivers::
370 The driver core will automatically attempt to bind this driver to any SPI
398 the SPI device using "struct spi_message". When remove() returns,
403 as one atomic sequence. SPI driver controls include:
464 of interacting with SPI devices.
480 How do I write an "SPI Master Controller Driver"?
482 An SPI controller will probably be registered on the platform_bus; write
502 used to interact with the SPI core and SPI protocol drivers. It will
511 If you need to remove your SPI controller driver, spi_unregister_master()
519 SPI bus (shared SCK, MOSI, MISO). Valid bus numbers start at zero. On
530 SPI Master Methods
534 This sets up the device clock rate, SPI mode, and word sizes.
538 Unless each SPI slave has its own configuration registers, don't
540 that's in progress for other SPI devices.
588 This method allows SPI client drivers to request SPI master controller
605 SPI Message Queue
609 SPI subsystem, just implement the queued methods specified above. Using
612 can also be elevated to realtime priority on high-priority SPI traffic.
614 Unless the queueing mechanism in the SPI subsystem is selected, the bulk
622 often DMA (especially if the root filesystem is in SPI flash), and
632 Contributors to Linux-SPI discussions include (in alphabetical order,