mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
108 lines
3.3 KiB
108 lines
3.3 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
|
/* |
|
* 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; |
|
} |
|
|
|
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; |
|
}
|
|
|