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spi: new spi->mode bits
Add two new spi_device.mode bits to accomodate more protocol options, and pass them through to usermode drivers: * SPI_NO_CS ... a second 3-wire variant, where the chipselect line is removed instead of a data line; transfers are still full duplex. This obviously has STRONG protocol implications since the chipselect transitions can't be used to synchronize state transitions with the SPI master. * SPI_READY ... defines open drain signal that's pulled low to pause the clock. This defines a 5-wire variant (normal 4-wire SPI plus READY) and two 4-wire variants (READY plus each of the 3-wire flavors). Such hardware flow control can be a big win. There are ADC converters and flash chips that expose READY signals, but not many host controllers support it today. The spi_bitbang code should be changed to use SPI_NO_CS instead of its current nonportable hack. That's a mode most hardware can easily support (unlike SPI_READY). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: "Paulraj, Sandeep" <s-paulraj@ti.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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c49568235d
commit
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4 changed files with 24 additions and 7 deletions
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@ -99,11 +99,13 @@ void parse_opts(int argc, char *argv[])
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{ "lsb", 0, 0, 'L' },
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{ "lsb", 0, 0, 'L' },
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{ "cs-high", 0, 0, 'C' },
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{ "cs-high", 0, 0, 'C' },
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{ "3wire", 0, 0, '3' },
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{ "3wire", 0, 0, '3' },
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{ "no-cs", 0, 0, 'N' },
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{ "ready", 0, 0, 'R' },
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{ NULL, 0, 0, 0 },
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{ NULL, 0, 0, 0 },
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};
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};
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int c;
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int c;
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c = getopt_long(argc, argv, "D:s:d:b:lHOLC3", lopts, NULL);
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c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL);
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if (c == -1)
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if (c == -1)
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break;
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break;
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@ -139,6 +141,12 @@ void parse_opts(int argc, char *argv[])
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case '3':
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case '3':
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mode |= SPI_3WIRE;
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mode |= SPI_3WIRE;
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break;
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break;
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case 'N':
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mode |= SPI_NO_CS;
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break;
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case 'R':
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mode |= SPI_READY;
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break;
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default:
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default:
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print_usage(argv[0]);
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print_usage(argv[0]);
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break;
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break;
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@ -58,15 +58,20 @@ static unsigned long minors[N_SPI_MINORS / BITS_PER_LONG];
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/* Bit masks for spi_device.mode management. Note that incorrect
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/* Bit masks for spi_device.mode management. Note that incorrect
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* settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
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* settings for some settings can cause *lots* of trouble for other
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* devices on a shared bus: CS_HIGH, because this device will be
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* devices on a shared bus:
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* active when it shouldn't be; 3WIRE, because when active it won't
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* behave as it should.
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*
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*
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* REVISIT should changing those two modes be privileged?
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* - CS_HIGH ... this device will be active when it shouldn't be
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* - 3WIRE ... when active, it won't behave as it should
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* - NO_CS ... there will be no explicit message boundaries; this
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* is completely incompatible with the shared bus model
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* - READY ... transfers may proceed when they shouldn't.
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*
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* REVISIT should changing those flags be privileged?
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*/
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*/
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#define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
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#define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
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| SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
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| SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
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| SPI_NO_CS | SPI_READY)
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struct spidev_data {
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struct spidev_data {
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dev_t devt;
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dev_t devt;
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@ -80,6 +80,8 @@ struct spi_device {
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#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
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#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
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#define SPI_3WIRE 0x10 /* SI/SO signals shared */
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#define SPI_3WIRE 0x10 /* SI/SO signals shared */
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#define SPI_LOOP 0x20 /* loopback mode */
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#define SPI_LOOP 0x20 /* loopback mode */
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#define SPI_NO_CS 0x40 /* 1 dev/bus, no chipselect */
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#define SPI_READY 0x80 /* slave pulls low to pause */
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u8 bits_per_word;
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u8 bits_per_word;
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int irq;
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int irq;
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void *controller_state;
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void *controller_state;
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@ -40,6 +40,8 @@
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#define SPI_LSB_FIRST 0x08
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#define SPI_LSB_FIRST 0x08
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#define SPI_3WIRE 0x10
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#define SPI_3WIRE 0x10
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#define SPI_LOOP 0x20
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#define SPI_LOOP 0x20
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#define SPI_NO_CS 0x40
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#define SPI_READY 0x80
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/*---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------*/
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