From 961d13ee1a903c30008a625ba7e03631e4903999 Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Sat, 27 Jul 2019 11:57:14 -0400
Subject: [PATCH] stm32f4: Add support for SPI

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 src/stm32f4/Kconfig  |  2 ++
 src/stm32f4/Makefile |  1 +
 src/stm32f4/gpio.h   |  9 +++++++
 src/stm32f4/spi.c    | 57 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 69 insertions(+)
 create mode 100644 src/stm32f4/spi.c

diff --git a/src/stm32f4/Kconfig b/src/stm32f4/Kconfig
index df2036ab..7edf61b5 100644
--- a/src/stm32f4/Kconfig
+++ b/src/stm32f4/Kconfig
@@ -7,6 +7,8 @@ config STM32F4_SELECT
     default y
     select HAVE_GPIO
     select HAVE_GPIO_ADC
+    select HAVE_GPIO_SPI
+    select HAVE_GPIO_BITBANGING
 
 config BOARD_DIRECTORY
     string
diff --git a/src/stm32f4/Makefile b/src/stm32f4/Makefile
index b1c22cb7..1586a36f 100644
--- a/src/stm32f4/Makefile
+++ b/src/stm32f4/Makefile
@@ -16,6 +16,7 @@ src-y += generic/crc16_ccitt.c generic/alloc.c
 src-y += generic/armcm_irq.c generic/armcm_timer.c
 src-y += ../lib/stm32f4/system_stm32f4xx.c
 src-$(CONFIG_HAVE_GPIO_ADC) += stm32f4/adc.c
+src-$(CONFIG_HAVE_GPIO_SPI) += stm32f4/spi.c
 src-$(CONFIG_SERIAL) += stm32f4/serial.c generic/serial_irq.c
 
 # Add assembler build rules
diff --git a/src/stm32f4/gpio.h b/src/stm32f4/gpio.h
index 6aaf02c3..01c01a1e 100644
--- a/src/stm32f4/gpio.h
+++ b/src/stm32f4/gpio.h
@@ -29,4 +29,13 @@ uint32_t gpio_adc_sample(struct gpio_adc g);
 uint16_t gpio_adc_read(struct gpio_adc g);
 void gpio_adc_cancel_sample(struct gpio_adc g);
 
+struct spi_config {
+    void *spidev;
+    uint32_t spi_cr1;
+};
+struct spi_config spi_setup(uint32_t bus, uint8_t mode, uint32_t rate);
+void spi_prepare(struct spi_config config);
+void spi_transfer(struct spi_config config, uint8_t receive_data
+                  , uint8_t len, uint8_t *data);
+
 #endif // gpio.h
diff --git a/src/stm32f4/spi.c b/src/stm32f4/spi.c
new file mode 100644
index 00000000..3759f286
--- /dev/null
+++ b/src/stm32f4/spi.c
@@ -0,0 +1,57 @@
+// SPI functions on STM32F4
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "command.h" // shutdown
+#include "gpio.h" // spi_setup
+#include "internal.h" // gpio_peripheral
+#include "sched.h" // sched_shutdown
+
+DECL_ENUMERATION("spi_bus", "spi2", 0);
+DECL_CONSTANT_STR("BUS_PINS_spi2", "PB14,PB15,PB13");
+
+struct spi_config
+spi_setup(uint32_t bus, uint8_t mode, uint32_t rate)
+{
+    if (bus)
+        shutdown("Invalid spi bus");
+
+    // Enable SPI
+    enable_pclock(SPI2_BASE);
+    gpio_peripheral(GPIO('B', 14), GPIO_FUNCTION, 5, 1);
+    gpio_peripheral(GPIO('B', 15), GPIO_FUNCTION, 5, 0);
+    gpio_peripheral(GPIO('B', 13), GPIO_FUNCTION, 5, 0);
+
+    // Calculate CR1 register
+    uint32_t pclk = get_pclock_frequency(SPI2_BASE);
+    uint32_t div = 0;
+    while ((pclk >> (div + 1)) > rate && div < 7)
+        div++;
+    uint32_t cr1 = ((mode << SPI_CR1_CPHA_Pos) | (div << SPI_CR1_BR_Pos)
+                    | SPI_CR1_SPE | SPI_CR1_MSTR | SPI_CR1_SSM | SPI_CR1_SSI);
+
+    return (struct spi_config){ .spi_cr1 = cr1 };
+}
+
+void
+spi_prepare(struct spi_config config)
+{
+    SPI2->CR1 = config.spi_cr1;
+}
+
+void
+spi_transfer(struct spi_config config, uint8_t receive_data,
+             uint8_t len, uint8_t *data)
+{
+    while (len--) {
+        SPI2->DR = *data;
+        while (!(SPI2->SR & SPI_SR_RXNE))
+            ;
+        uint8_t rdata = SPI2->DR;
+        if (receive_data)
+            *data = rdata;
+        data++;
+    }
+}