Lines Matching +full:sleep +full:- +full:hardware +full:- +full:state
5 02-Feb-2012
8 ------------
17 clocking modes through which data is exchanged; mode-0 and mode-3 are most
32 - SPI may be used for request/response style device protocols, as with
35 - It may also be used to stream data in either direction (half duplex),
38 - Some devices may use eight bit words. Others may use different word
39 lengths, such as streams of 12-bit or 20-bit digital samples.
41 - Words are usually sent with their most significant bit (MSB) first,
44 - Sometimes SPI is used to daisy-chain devices, like shift registers.
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
58 limiting themselves to half-duplex at the hardware level. In fact
71 ---------------------------------------
76 support only SPI.) Some PC hardware uses SPI flash for BIOS code.
88 appropriate low-pincount peripheral bus.
96 -----------------------------------------------------
100 - CPOL indicates the initial clock polarity. CPOL=0 means the
105 - CPHA indicates the clock phase used to sample data; CPHA=0 says
129 ------------------------------------------------
144 controllers may be built into System-On-Chip
146 These drivers touch hardware registers and may use DMA.
160 A "struct spi_device" encapsulates the controller-side interface between
182 class related state for the SPI host controller managing bus "B".
195 class related state for the SPI target controller on bus "B". When
199 At this time, the only class-specific state is the bus number ("B" in "spiB"),
203 How does board-specific init code declare SPI devices?
204 ------------------------------------------------------
206 That information is normally provided by board-specific code, even for
213 For System-on-Chip (SOC) based boards, these will usually be platform
220 the arch/.../mach-*/board-*.c files for several boards can all share the
222 SPI-capable controllers, and only the ones actually usable on a given
225 So for example arch/.../mach-*/board-*.c files might have code like::
229 /* if your mach-* infrastructure doesn't support kernels that can
242 And SOC-specific utility code might look something like::
256 spi2->dev.platform_data = pdata2;
277 on the target board, often with some board-specific data needed for the
280 Normally your arch/.../mach-*/board-*.c files would provide a small table
302 Again, notice how board-specific information is provided; each chip may need
305 is wired, plus chip-specific constraints like an important delay that's
309 controller driver. An example would be peripheral-specific DMA tuning
324 Like with other static board-specific setup, you won't unregister those.
328 your ``arch/.../mach-.../board-*.c`` file would primarily provide information
333 Non-static Configurations
342 ----------------------------------------
370 /* assuming the driver requires board-specific data: */
371 pdata = &spi->dev.platform_data;
373 return -ENODEV;
375 /* get memory for driver's per-chip state */
378 return -ENOMEM;
390 - An spi_message is a sequence of protocol operations, executed
416 - Follow standard kernel rules, and provide DMA-safe buffers in
418 to make extra copies unless the hardware requires it (e.g. working
419 around hardware errata that force the use of bounce buffering).
421 - The basic I/O primitive is spi_async(). Async requests may be
427 - There are also synchronous wrappers like spi_sync(), and wrappers
429 may be issued only in contexts that may sleep, and they're all
432 - The spi_write_then_read() call, and convenience wrappers around
435 common RPC-style requests, such as writing an eight bit command
436 and reading a sixteen bit response -- spi_w8r16() being one its
453 - I/O buffers use the usual Linux rules, and must be DMA-safe.
457 - The spi_message and spi_transfer metadata used to glue those
460 other allocate-once driver data structures. Zero-init these.
463 routines are available to allocate and zero-initialize an spi_message
468 -------------------------------------------------
474 spi_controller_get_devdata() to get the driver-private data allocated for that
484 return -ENODEV;
491 its own internal state. (See below about bus numbering and those methods.)
508 manufacturer. For example, hardware controller SPI2 would be bus number 2,
511 If you don't have such hardware-assigned bus number, and for some reason
514 this as a non-static configuration (see above).
520 ``ctlr->setup(struct spi_device *spi)``
523 call spi_setup(spi) to invoke this routine. It may sleep.
536 ``ctlr->cleanup(struct spi_device *spi)``
538 state it dynamically associates with that device. If you do that,
539 be sure to provide the cleanup() method to free that state.
541 ``ctlr->prepare_transfer_hardware(struct spi_controller *ctlr)``
544 driver to prepare the transfer hardware by issuing this call.
545 This may sleep.
547 ``ctlr->unprepare_transfer_hardware(struct spi_controller *ctlr)``
550 relax the hardware (e.g. by power management calls). This may sleep.
552 ``ctlr->transfer_one_message(struct spi_controller *ctlr, struct spi_message *mesg)``
557 message. This may sleep.
559 ``ctrl->transfer_one(struct spi_controller *ctlr, struct spi_device *spi, struct spi_transfer *tran…
564 transfer. This may sleep. Note: transfer_one and transfer_one_message
574 ``ctrl->set_cs_timing(struct spi_device *spi, u8 setup_clk_cycles, u8 hold_clk_cycles, u8 inactive_…
582 ``ctrl->transfer(struct spi_device *spi, struct spi_message *message)``
583 This must not sleep. Its responsibility is to arrange that the
598 providing pure process-context execution of methods. The message queue
599 can also be elevated to realtime priority on high-priority SPI traffic.
606 for low-frequency sensor access might be fine using synchronous PIO.
608 But the queue will probably be very real, using message->queue, PIO,
618 ------------------------------
650 that other SPI protocols don't (e.g. data line state for when CS is not
654 MOSI idle state configuration
657 Common SPI protocol implementations don't specify any state or behavior for the
659 peripherals that require specific MOSI line state when data is not being clocked
688 In this extension to the usual SPI protocol, the MOSI line state is specified to
701 ---------
702 Contributors to Linux-SPI discussions include (in alphabetical order,
705 - Mark Brown
706 - David Brownell
707 - Russell King
708 - Grant Likely
709 - Dmitry Pervushin
710 - Stephen Street
711 - Mark Underwood
712 - Andrew Victor
713 - Linus Walleij
714 - Vitaly Wool