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author | hartleys <hartleys@visionengravers.com> | 2010-05-06 20:51:04 +0000 |
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committer | Grant Likely <grant.likely@secretlab.ca> | 2010-05-25 00:23:17 -0600 |
commit | 41c4221ca6b9db8ea63d2c2323c0e7a8865eba6e (patch) | |
tree | 31e12f709964805f9d73cf834297950b9ad09000 /drivers/spi/spi_bitbang_txrx.h | |
parent | 6e27388f1bd60b55e0b1a83d14233e6c7ad33700 (diff) | |
download | lwn-41c4221ca6b9db8ea63d2c2323c0e7a8865eba6e.tar.gz lwn-41c4221ca6b9db8ea63d2c2323c0e7a8865eba6e.zip |
spi: move bitbang txrx utility functions to private header
A number of files in drivers/spi fail checkincludes.pl due to the double
include of <linux/spi/spi_bitbang.h>.
The first include is needed to get the struct spi_bitbang definition and
the spi_bitbang_* function prototypes.
The second include happens after defining EXPAND_BITBANG_TXRX to get the
inlined bitbang_txrx_* utility functions.
The <linux/spi/spi_bitbang.h> header is also included by a number of other
spi drivers, as well as some arch/ code, in order to use struct spi_bitbang
and the associated functions.
To fix the double include, and remove any potential confusion about it, move
the inlined bitbang_txrx_* functions to a new private header in drivers/spi
and also remove the need to define EXPAND_BITBANG_TXRX.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Diffstat (limited to 'drivers/spi/spi_bitbang_txrx.h')
-rw-r--r-- | drivers/spi/spi_bitbang_txrx.h | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/drivers/spi/spi_bitbang_txrx.h b/drivers/spi/spi_bitbang_txrx.h new file mode 100644 index 000000000000..fc033bbf9180 --- /dev/null +++ b/drivers/spi/spi_bitbang_txrx.h @@ -0,0 +1,93 @@ +/* + * Mix this utility code with some glue code to get one of several types of + * simple SPI master driver. Two do polled word-at-a-time I/O: + * + * - GPIO/parport bitbangers. Provide chipselect() and txrx_word[](), + * expanding the per-word routines from the inline templates below. + * + * - Drivers for controllers resembling bare shift registers. Provide + * chipselect() and txrx_word[](), with custom setup()/cleanup() methods + * that use your controller's clock and chipselect registers. + * + * Some hardware works well with requests at spi_transfer scope: + * + * - Drivers leveraging smarter hardware, with fifos or DMA; or for half + * duplex (MicroWire) controllers. Provide chipselect() and txrx_bufs(), + * and custom setup()/cleanup() methods. + */ + +/* + * The code that knows what GPIO pins do what should have declared four + * functions, ideally as inlines, before including this header: + * + * void setsck(struct spi_device *, int is_on); + * void setmosi(struct spi_device *, int is_on); + * int getmiso(struct spi_device *); + * void spidelay(unsigned); + * + * setsck()'s is_on parameter is a zero/nonzero boolean. + * + * setmosi()'s is_on parameter is a zero/nonzero boolean. + * + * getmiso() is required to return 0 or 1 only. Any other value is invalid + * and will result in improper operation. + * + * A non-inlined routine would call bitbang_txrx_*() routines. The + * main loop could easily compile down to a handful of instructions, + * especially if the delay is a NOP (to run at peak speed). + * + * Since this is software, the timings may not be exactly what your board's + * chips need ... there may be several reasons you'd need to tweak timings + * in these routines, not just make to make it faster or slower to match a + * particular CPU clock rate. + */ + +static inline u32 +bitbang_txrx_be_cpha0(struct spi_device *spi, + unsigned nsecs, unsigned cpol, + u32 word, u8 bits) +{ + /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ + + /* clock starts at inactive polarity */ + for (word <<= (32 - bits); likely(bits); bits--) { + + /* setup MSB (to slave) on trailing edge */ + setmosi(spi, word & (1 << 31)); + spidelay(nsecs); /* T(setup) */ + + setsck(spi, !cpol); + spidelay(nsecs); + + /* sample MSB (from slave) on leading edge */ + word <<= 1; + word |= getmiso(spi); + setsck(spi, cpol); + } + return word; +} + +static inline u32 +bitbang_txrx_be_cpha1(struct spi_device *spi, + unsigned nsecs, unsigned cpol, + u32 word, u8 bits) +{ + /* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */ + + /* clock starts at inactive polarity */ + for (word <<= (32 - bits); likely(bits); bits--) { + + /* setup MSB (to slave) on leading edge */ + setsck(spi, !cpol); + setmosi(spi, word & (1 << 31)); + spidelay(nsecs); /* T(setup) */ + + setsck(spi, cpol); + spidelay(nsecs); + + /* sample MSB (from slave) on trailing edge */ + word <<= 1; + word |= getmiso(spi); + } + return word; +} |