| Angel Pons | 8a3453f | 2020-04-02 23:48:19 +0200 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
| Julius Werner | 4783db2 | 2018-03-27 16:28:52 -0700 | [diff] [blame] | 2 | |
| 3 | #include <console/console.h> |
| 4 | #include <delay.h> |
| 5 | #include <spi_bitbang.h> |
| Elyes Haouas | 69451f1 | 2022-10-07 10:08:53 +0200 | [diff] [blame] | 6 | #include <types.h> |
| Julius Werner | 4783db2 | 2018-03-27 16:28:52 -0700 | [diff] [blame] | 7 | |
| 8 | /* Set to 1 to dump all SPI transfers to the UART. */ |
| 9 | #define TRACE 0 |
| 10 | /* |
| 11 | * In theory, this should work fine with 0 delay since the bus is fully clocked |
| 12 | * by the master and the slave just needs to follow clock transitions whenever |
| 13 | * they happen. We're not going to be "too fast" by bit-banging anyway. However, |
| 14 | * if something doesn't work right, try increasing this value to slow it down. |
| 15 | */ |
| 16 | #define HALF_CLOCK_US 0 |
| 17 | |
| 18 | int spi_bitbang_claim_bus(const struct spi_bitbang_ops *ops) |
| 19 | { |
| 20 | ops->set_cs(ops, 0); |
| 21 | return 0; |
| 22 | } |
| 23 | |
| 24 | void spi_bitbang_release_bus(const struct spi_bitbang_ops *ops) |
| 25 | { |
| 26 | ops->set_cs(ops, 1); |
| 27 | } |
| 28 | |
| 29 | /* Implements a CPOL=0, CPH=0, MSB first 8-bit controller. */ |
| 30 | int spi_bitbang_xfer(const struct spi_bitbang_ops *ops, const void *dout, |
| 31 | size_t bytes_out, void *din, size_t bytes_in) |
| 32 | { |
| 33 | if (TRACE) { |
| 34 | if (bytes_in && bytes_out) |
| 35 | printk(BIOS_SPEW, "!"); |
| 36 | else if (bytes_in) |
| 37 | printk(BIOS_SPEW, "<"); |
| 38 | else if (bytes_out) |
| 39 | printk(BIOS_SPEW, ">"); |
| 40 | } |
| 41 | |
| 42 | while (bytes_out || bytes_in) { |
| 43 | int i; |
| 44 | uint8_t in_byte = 0, out_byte = 0; |
| 45 | if (bytes_out) { |
| 46 | out_byte = *(const uint8_t *)dout++; |
| 47 | bytes_out--; |
| 48 | if (TRACE) |
| 49 | printk(BIOS_SPEW, "%02x", out_byte); |
| 50 | } |
| 51 | for (i = 7; i >= 0; i--) { |
| 52 | ops->set_mosi(ops, !!(out_byte & (1 << i))); |
| 53 | if (HALF_CLOCK_US) |
| 54 | udelay(HALF_CLOCK_US); |
| 55 | ops->set_clk(ops, 1); |
| 56 | in_byte |= !!ops->get_miso(ops) << i; |
| 57 | if (HALF_CLOCK_US) |
| 58 | udelay(HALF_CLOCK_US); |
| 59 | ops->set_clk(ops, 0); |
| 60 | } |
| 61 | if (bytes_in) { |
| 62 | *(uint8_t *)din++ = in_byte; |
| 63 | bytes_in--; |
| 64 | if (TRACE) |
| 65 | printk(BIOS_SPEW, "%02x", in_byte); |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | if (TRACE) |
| 70 | printk(BIOS_SPEW, "\n"); |
| 71 | return 0; |
| 72 | } |