From b55f627feeb9d48fdbde3835e18afbc76712e49b Mon Sep 17 00:00:00 2001 From: David Brownell Date: Tue, 30 Jun 2009 11:41:26 -0700 Subject: [PATCH] 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 Cc: "Paulraj, Sandeep" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/spi/spidev_test.c | 10 +++++++++- drivers/spi/spidev.c | 17 +++++++++++------ include/linux/spi/spi.h | 2 ++ include/linux/spi/spidev.h | 2 ++ 4 files changed, 24 insertions(+), 7 deletions(-) diff --git a/Documentation/spi/spidev_test.c b/Documentation/spi/spidev_test.c index cf0e3ce0d526..c1a5aad3c75a 100644 --- a/Documentation/spi/spidev_test.c +++ b/Documentation/spi/spidev_test.c @@ -99,11 +99,13 @@ void parse_opts(int argc, char *argv[]) { "lsb", 0, 0, 'L' }, { "cs-high", 0, 0, 'C' }, { "3wire", 0, 0, '3' }, + { "no-cs", 0, 0, 'N' }, + { "ready", 0, 0, 'R' }, { NULL, 0, 0, 0 }, }; int c; - c = getopt_long(argc, argv, "D:s:d:b:lHOLC3", lopts, NULL); + c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL); if (c == -1) break; @@ -139,6 +141,12 @@ void parse_opts(int argc, char *argv[]) case '3': mode |= SPI_3WIRE; break; + case 'N': + mode |= SPI_NO_CS; + break; + case 'R': + mode |= SPI_READY; + break; default: print_usage(argv[0]); break; diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index 5d869c4d3eb2..606e7a40a8da 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -58,15 +58,20 @@ static unsigned long minors[N_SPI_MINORS / BITS_PER_LONG]; /* Bit masks for spi_device.mode management. Note that incorrect - * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other - * devices on a shared bus: CS_HIGH, because this device will be - * active when it shouldn't be; 3WIRE, because when active it won't - * behave as it should. + * settings for some settings can cause *lots* of trouble for other + * devices on a shared bus: * - * REVISIT should changing those two modes be privileged? + * - CS_HIGH ... this device will be active when it shouldn't be + * - 3WIRE ... when active, it won't behave as it should + * - NO_CS ... there will be no explicit message boundaries; this + * is completely incompatible with the shared bus model + * - READY ... transfers may proceed when they shouldn't. + * + * REVISIT should changing those flags be privileged? */ #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \ - | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP) + | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \ + | SPI_NO_CS | SPI_READY) struct spidev_data { dev_t devt; diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 9c4cd27f4685..743c933ac4e7 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -80,6 +80,8 @@ struct spi_device { #define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */ #define SPI_3WIRE 0x10 /* SI/SO signals shared */ #define SPI_LOOP 0x20 /* loopback mode */ +#define SPI_NO_CS 0x40 /* 1 dev/bus, no chipselect */ +#define SPI_READY 0x80 /* slave pulls low to pause */ u8 bits_per_word; int irq; void *controller_state; diff --git a/include/linux/spi/spidev.h b/include/linux/spi/spidev.h index 95251ccd5a07..bf0570a84f7a 100644 --- a/include/linux/spi/spidev.h +++ b/include/linux/spi/spidev.h @@ -40,6 +40,8 @@ #define SPI_LSB_FIRST 0x08 #define SPI_3WIRE 0x10 #define SPI_LOOP 0x20 +#define SPI_NO_CS 0x40 +#define SPI_READY 0x80 /*---------------------------------------------------------------------------*/