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author | Stephen Rothwell <sfr@canb.auug.org.au> | 2011-07-25 21:59:46 +0400 |
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committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2011-07-25 22:53:52 +0400 |
commit | 5f00bcb38ef9a980a33c6dbdc0044964b05f22dd (patch) | |
tree | 3175fb9375aecb50bde1be0bf4fa8aa8155131d6 /drivers/spi/spi-bitbang-txrx.h | |
parent | 34006cee28f7344f9557a4be3816c7891b1bbab1 (diff) | |
parent | b6844e8f64920cdee620157252169ba63afb0c89 (diff) | |
download | linux-5f00bcb38ef9a980a33c6dbdc0044964b05f22dd.tar.xz |
Merge branch 'master' into devel and apply fixup from Stephen Rothwell:
vfs/nfs: fixup for nfs_open_context change
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'drivers/spi/spi-bitbang-txrx.h')
-rw-r--r-- | drivers/spi/spi-bitbang-txrx.h | 97 |
1 files changed, 97 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..c16bf853c3eb --- /dev/null +++ b/drivers/spi/spi-bitbang-txrx.h @@ -0,0 +1,97 @@ +/* + * 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, unsigned flags, + 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 */ + if ((flags & SPI_MASTER_NO_TX) == 0) + setmosi(spi, word & (1 << 31)); + spidelay(nsecs); /* T(setup) */ + + setsck(spi, !cpol); + spidelay(nsecs); + + /* sample MSB (from slave) on leading edge */ + word <<= 1; + if ((flags & SPI_MASTER_NO_RX) == 0) + word |= getmiso(spi); + setsck(spi, cpol); + } + return word; +} + +static inline u32 +bitbang_txrx_be_cpha1(struct spi_device *spi, + unsigned nsecs, unsigned cpol, unsigned flags, + 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); + if ((flags & SPI_MASTER_NO_TX) == 0) + setmosi(spi, word & (1 << 31)); + spidelay(nsecs); /* T(setup) */ + + setsck(spi, cpol); + spidelay(nsecs); + + /* sample MSB (from slave) on trailing edge */ + word <<= 1; + if ((flags & SPI_MASTER_NO_RX) == 0) + word |= getmiso(spi); + } + return word; +} |