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https://github.com/ARM-software/arm-trusted-firmware.git
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3c54570afc
When using a tpm breakout board with rpi3, we elected to bit-bang gpio pins to emulate a spi interface, this implementation required a driver to interface with the platform specific pins and emulate spi functionality. The generic driver provides the ability to pass in a gpio_spi_data structure that contains the necessary gpio pins in order to simulate spi operations (get_access, start, stop, xfer). Change-Id: I88919e8a294c05e0cabb8224e35ae5c1ba5f2413 Signed-off-by: Tushar Khandelwal <tushar.khandelwal@arm.com> Signed-off-by: Abhi Singh <abhi.singh@arm.com>
130 lines
2.4 KiB
C
130 lines
2.4 KiB
C
/*
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* Copyright (c) 2025, ARM Limited and Contributors. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <common/debug.h>
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#include <drivers/delay_timer.h>
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#include <drivers/gpio.h>
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#include <drivers/gpio_spi.h>
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#include <platform_def.h>
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static struct spi_plat gpio_spidev;
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static void gpio_spi_delay_us(void)
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{
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udelay(gpio_spidev.gpio_data.spi_delay_us);
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}
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static int gpio_spi_miso(void)
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{
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return gpio_get_value(gpio_spidev.gpio_data.miso_gpio);
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}
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static void gpio_spi_sclk(int bit)
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{
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gpio_set_value(gpio_spidev.gpio_data.sclk_gpio, bit);
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}
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static void gpio_spi_mosi(int bit)
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{
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gpio_set_value(gpio_spidev.gpio_data.mosi_gpio, bit);
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}
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static void gpio_spi_cs(int bit)
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{
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gpio_set_value(gpio_spidev.gpio_data.cs_gpio, bit);
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}
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static void gpio_spi_start(void)
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{
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gpio_spi_cs(1);
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gpio_spi_sclk(0);
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gpio_spi_cs(0);
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}
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static void gpio_spi_stop(void)
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{
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gpio_spi_cs(1);
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}
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/* set sclk to a known state (0) before performing any further action */
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static void gpio_spi_get_access(void)
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{
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gpio_spi_sclk(0);
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}
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static void xfer(unsigned int bytes, const void *out, void *in, int cpol, int cpha)
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{
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for (unsigned int j = 0U; j < bytes; j++) {
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unsigned char in_byte = 0U;
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unsigned char out_byte = (out != NULL) ? *(const uint8_t *)out++ : 0xFF;
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for (int i = 7; i >= 0; i--) {
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if (cpha) {
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gpio_spi_sclk(!cpol);
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}
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gpio_spi_mosi(!!(out_byte & (1 << i)));
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gpio_spi_delay_us();
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gpio_spi_sclk(cpha ? cpol : !cpol);
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gpio_spi_delay_us();
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in_byte |= gpio_spi_miso() << i;
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if (!cpha) {
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gpio_spi_sclk(cpol);
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}
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}
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if (in != NULL) {
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*(uint8_t *)in++ = in_byte;
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}
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}
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}
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static int gpio_spi_xfer(unsigned int bytes, const void *out, void *in)
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{
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if ((out == NULL) && (in == NULL)) {
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return -1;
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}
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switch (gpio_spidev.gpio_data.spi_mode) {
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case 0:
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xfer(bytes, out, in, 0, 0);
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break;
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case 1:
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xfer(bytes, out, in, 0, 1);
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break;
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case 2:
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xfer(bytes, out, in, 1, 0);
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break;
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case 3:
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xfer(bytes, out, in, 1, 1);
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break;
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default:
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return -1;
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}
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return 0;
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}
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struct spi_ops gpio_spidev_ops = {
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.get_access = gpio_spi_get_access,
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.start = gpio_spi_start,
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.stop = gpio_spi_stop,
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.xfer = gpio_spi_xfer,
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};
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struct spi_plat *gpio_spi_init(struct gpio_spi_data *gpio_spi_data)
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{
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gpio_spidev.gpio_data = *gpio_spi_data;
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gpio_spidev.ops = &gpio_spidev_ops;
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return &gpio_spidev;
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}
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