| /* SPDX-License-Identifier: GPL-2.0-only */ |
| |
| #include <console/console.h> |
| #include <delay.h> |
| #include <spi_bitbang.h> |
| #include <types.h> |
| |
| /* Set to 1 to dump all SPI transfers to the UART. */ |
| #define TRACE 0 |
| /* |
| * In theory, this should work fine with 0 delay since the bus is fully clocked |
| * by the master and the slave just needs to follow clock transitions whenever |
| * they happen. We're not going to be "too fast" by bit-banging anyway. However, |
| * if something doesn't work right, try increasing this value to slow it down. |
| */ |
| #define HALF_CLOCK_US 0 |
| |
| int spi_bitbang_claim_bus(const struct spi_bitbang_ops *ops) |
| { |
| ops->set_cs(ops, 0); |
| return 0; |
| } |
| |
| void spi_bitbang_release_bus(const struct spi_bitbang_ops *ops) |
| { |
| ops->set_cs(ops, 1); |
| } |
| |
| /* Implements a CPOL=0, CPH=0, MSB first 8-bit controller. */ |
| int spi_bitbang_xfer(const struct spi_bitbang_ops *ops, const void *dout, |
| size_t bytes_out, void *din, size_t bytes_in) |
| { |
| if (TRACE) { |
| if (bytes_in && bytes_out) |
| printk(BIOS_SPEW, "!"); |
| else if (bytes_in) |
| printk(BIOS_SPEW, "<"); |
| else if (bytes_out) |
| printk(BIOS_SPEW, ">"); |
| } |
| |
| while (bytes_out || bytes_in) { |
| int i; |
| uint8_t in_byte = 0, out_byte = 0; |
| if (bytes_out) { |
| out_byte = *(const uint8_t *)dout++; |
| bytes_out--; |
| if (TRACE) |
| printk(BIOS_SPEW, "%02x", out_byte); |
| } |
| for (i = 7; i >= 0; i--) { |
| ops->set_mosi(ops, !!(out_byte & (1 << i))); |
| if (HALF_CLOCK_US) |
| udelay(HALF_CLOCK_US); |
| ops->set_clk(ops, 1); |
| in_byte |= !!ops->get_miso(ops) << i; |
| if (HALF_CLOCK_US) |
| udelay(HALF_CLOCK_US); |
| ops->set_clk(ops, 0); |
| } |
| if (bytes_in) { |
| *(uint8_t *)din++ = in_byte; |
| bytes_in--; |
| if (TRACE) |
| printk(BIOS_SPEW, "%02x", in_byte); |
| } |
| } |
| |
| if (TRACE) |
| printk(BIOS_SPEW, "\n"); |
| return 0; |
| } |