cregit-Linux how code gets into the kernel

Release 4.10 drivers/spi/spi-bitbang-txrx.h

Directory: drivers/spi
/*
 * 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 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 */ u32 oldbit = (!(word & (1<<(bits-1)))) << 31; /* 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) { if ((word & (1 << 31)) != oldbit) { setmosi(spi, word & (1 << 31)); oldbit = 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; }

Contributors

PersonTokensPropCommitsCommitProp
h hartley sweetenh hartley sweeten10158.05%125.00%
michael grzeschikmichael grzeschik3721.26%125.00%
marek szyprowskimarek szyprowski2313.22%125.00%
lars perssonlars persson137.47%125.00%
Total174100.00%4100.00%


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 */ u32 oldbit = (!(word & (1<<(bits-1)))) << 31; /* 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) { if ((word & (1 << 31)) != oldbit) { setmosi(spi, word & (1 << 31)); oldbit = 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; }

Contributors

PersonTokensPropCommitsCommitProp
h hartley sweetenh hartley sweeten10158.05%125.00%
michael grzeschikmichael grzeschik4022.99%125.00%
marek szyprowskimarek szyprowski2313.22%125.00%
lars perssonlars persson105.75%125.00%
Total174100.00%4100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
h hartley sweetenh hartley sweeten20358.00%120.00%
michael grzeschikmichael grzeschik7722.00%120.00%
marek szyprowskimarek szyprowski4613.14%120.00%
lars perssonlars persson236.57%120.00%
geert uytterhoevengeert uytterhoeven10.29%120.00%
Total350100.00%5100.00%
Directory: drivers/spi
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