diff options
Diffstat (limited to 'common/recipes-utils/bitbang/files/src/bitbang.c')
| -rw-r--r-- | common/recipes-utils/bitbang/files/src/bitbang.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/common/recipes-utils/bitbang/files/src/bitbang.c b/common/recipes-utils/bitbang/files/src/bitbang.c new file mode 100644 index 0000000..1318f42 --- /dev/null +++ b/common/recipes-utils/bitbang/files/src/bitbang.c @@ -0,0 +1,236 @@ +/* + * Copyright 2014-present Facebook. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ +//#define DEBUG +//#define VERBOSE + +#include "bitbang.h" + +#include <errno.h> +#include <fcntl.h> +#include <stdlib.h> +#include <string.h> +#include <time.h> +#include <sys/ioctl.h> +#include <sys/stat.h> +#include <sys/types.h> + +#include <openbmc/log.h> + +#define NANOSEC_IN_SEC (1000 * 1000 * 1000) + +#define BITBANG_FREQ_MAX (500 * 1000 * 1000) /* 500M Hz */ +#define BITBANG_FREQ_DEFAULT (1 * 1000 * 1000) /* 1M Hz */ + +#define MAX(a, b) (((a) > (b)) ? (a) : (b)) + +struct bitbang_handle { + bitbang_init_st bbh_init; + uint32_t bbh_half_clk; /* ns per clock cycle */ +}; + +void bitbang_init_default(bitbang_init_st *init) +{ + memset(init, sizeof(*init), 0); + init->bbi_clk_start = BITBANG_PIN_HIGH; + init->bbi_data_out = BITBANG_CLK_EDGE_FALLING; + init->bbi_data_in = BITBANG_CLK_EDGE_RISING; + init->bbi_freq = BITBANG_FREQ_DEFAULT; +} + +bitbang_handle_st* bitbang_open(const bitbang_init_st *init) +{ + bitbang_handle_st *hdl; + + if (!init || !init->bbi_pin_f + || !init->bbi_freq || init->bbi_freq > BITBANG_FREQ_MAX) { + LOG_ERR(EINVAL, "Invalid init structure"); + return NULL; + } + + hdl = calloc(1, sizeof(*hdl)); + if (!hdl) { + return NULL; + } + + hdl->bbh_init = *init; + hdl->bbh_half_clk = NANOSEC_IN_SEC / init->bbi_freq / 2; + + LOG_DBG("Bitbang open with initial %s, data out at %s, data in at %s, " + "freq at %uHz, half clk %uns", + (init->bbi_clk_start == BITBANG_PIN_LOW) ? "LOW" : "HIGH", + (init->bbi_data_out == BITBANG_CLK_EDGE_RISING) + ? "RISING" : "FALLING", + (init->bbi_data_in == BITBANG_CLK_EDGE_RISING) + ? "RISING" : "FALLING", + init->bbi_freq, hdl->bbh_half_clk); + + return hdl; +} + +void bitbang_close(bitbang_handle_st *hdl) +{ + free(hdl); +} + +/* + * The threshold (ns) to use spin instead of nanosleep(). + * Before adding the high resolution timer support, either spin or nanosleep() + * will not bring the process wakeup within 10ms. It turns out the system time + * update is also controlled by HZ (100). + * After I added the high resolution timer support, the spin works as the + * system time is updated more frequently. However, nanosleep() solution is + * still noticable slower comparing with spin. There could be some kernel + * scheduling tweak missing. Did not get time on that yet. + * For now, use 10ms as the threshold to determine if spin or nanosleep() + * is used. + */ +#define BITBANG_SPIN_THRESHOLD (10 * 1000 * 1000) + +static int sleep_ns(uint32_t clk) +{ + struct timespec req, rem; + int rc = 0; + if (clk <= BITBANG_SPIN_THRESHOLD) { + struct timespec orig; + rc = clock_gettime(CLOCK_MONOTONIC, &req); + orig = req; + while (!rc && clk) { + uint32_t tmp; + rc = clock_gettime(CLOCK_MONOTONIC, &rem); + tmp = (rem.tv_sec - req.tv_sec) * NANOSEC_IN_SEC; + if (rem.tv_nsec >= req.tv_nsec) { + tmp += rem.tv_nsec - req.tv_nsec; + } else { + tmp -= req.tv_nsec - rem.tv_nsec; + } + if (tmp >= clk) { + break; + } + clk -= tmp; + req = rem; + } + } else { + req.tv_sec = 0; + req.tv_nsec = clk; + while ((rc = nanosleep(&req, &rem)) == -1 && errno == EINTR) { + req = rem; + } + } + if (rc == -1) { + rc = errno; + LOG_ERR(rc, "Failed to sleep %u nanoseconds", clk); + } + return rc; +} + +int bitbang_io(const bitbang_handle_st *hdl, bitbang_io_st *io) +{ + int rc = 0; + uint32_t clk = hdl->bbh_half_clk; + const struct { + bitbang_pin_value_en value; + bitbang_clk_edge_en edge; + } clks[] = { + {BITBANG_PIN_HIGH, BITBANG_CLK_EDGE_FALLING}, + {BITBANG_PIN_LOW, BITBANG_CLK_EDGE_RISING}, + }; + int clk_idx; + int n_clk = 0; + int n_bits = 0; + const uint8_t *dout = io->bbio_dout; + uint8_t *din = io->bbio_din; + int bit_pos = 7; + bitbang_pin_func pin_f = hdl->bbh_init.bbi_pin_f; + void *context = hdl->bbh_init.bbi_context; + + if ((io->bbio_in_bits == 0 && io->bbio_din) + || (io->bbio_in_bits > 0 && !io->bbio_din)) { + rc = EINVAL; + LOG_ERR(rc, "Incorrect in bits and in buffer"); + goto out; + } + + if ((io->bbio_out_bits == 0 && io->bbio_dout) + || (io->bbio_out_bits > 0 && !io->bbio_dout)) { + rc = EINVAL; + LOG_ERR(rc, "Incorrect out bits and out buffer"); + goto out; + } + + if (io->bbio_in_bits == 0 && io->bbio_out_bits == 0) { + rc = EINVAL; + LOG_ERR(rc, "Both in and out bits are 0"); + goto out; + } + + if (hdl->bbh_init.bbi_clk_start == BITBANG_PIN_HIGH) { + clk_idx = 0; + } else { + clk_idx = 1; + } + + /* set the CLK pin start position */ + pin_f(BITBANG_CLK_PIN, clks[clk_idx].value, context); + + /* clear the first byte of din */ + if (din && io->bbio_in_bits) { + memset(din, 0, (io->bbio_in_bits + 7) / 8); + } + + do { + if ((rc = sleep_ns(clk))) { + goto out; + } + + /* output first */ + if (hdl->bbh_init.bbi_data_out == clks[clk_idx].edge) { + if (dout && n_bits < io->bbio_out_bits) { + pin_f(BITBANG_DATA_OUT, (*dout >> bit_pos) & 0x1, context); + } + } + + /* then, input */ + if (hdl->bbh_init.bbi_data_in == clks[clk_idx].edge) { + if (din && n_bits < io->bbio_in_bits) { + *din |= (pin_f(BITBANG_DATA_IN, 0, context) & 0x1) << bit_pos; + } + } + + if (++n_clk % 2 == 0) { + /* one bit for every 2 half clks */ + n_bits ++; + if (bit_pos == 0) { + if (dout) { + dout++; + } + if (din) { + din++; + } + bit_pos = 7; + } else { + bit_pos --; + } + } + clk_idx = 1 - clk_idx; + pin_f(BITBANG_CLK_PIN, clks[clk_idx].value, context); + } while (n_bits < MAX(io->bbio_in_bits, io->bbio_out_bits)); + + out: + + return -rc; +} |
