flash: Enable read/write/erase access flash from firmware.

src/board/system76/common/flash/main.c

@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) 2020 Evan Lojewski
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include <stdint.h>
+#include <board/flash.h>
+#include <flash/entry.h>
+
+// EC indirect flash access
+volatile uint8_t __xdata __at(0x103B) ECINDAR0;
+volatile uint8_t __xdata __at(0x103C) ECINDAR1;
+volatile uint8_t __xdata __at(0x103D) ECINDAR2;
+volatile uint8_t __xdata __at(0x103E) ECINDAR3;
+volatile uint8_t __xdata __at(0x103F) ECINDDR;
+
+#define SPI_DEVICE                  (0x70)
+#define SPI_FOLLOW_MODE             (0x0F)
+#define SPI_CHIP_SELECT             (0xFD)
+#define SPI_CHIP_DESELECT           (0xFE)
+
+#define SPI_READ_STATUS_COMMAND     (0x05)
+#define SPI_READ_COMMAND            (0x0B)
+#define SPI_WRITE_COMMAND           (0x02)
+#define SPI_WRITE_ENABLE_COMMAND    (0x06)
+#define SPI_READ_STATUS_COMMAND     (0x05)
+
+#define SPI_ERASE_SECTOR_COMMAND    (0xD7)
+
+#define SPI_STATUS_WIP              (0x01)
+
+void flash_enter_follow_mode(void);
+void flash_exit_follow_mode(void);
+void flash_wait(void);
+void flash_write_enable(void);
+
+/**
+ * Main flash API entry point.
+ *
+ * NOTE: This *must* be the first function in this file to ensure that it is placed
+ *          first in the resulting binary. This is required to ensure that address
+ *          matches the address (FLASH_OFFSET) for flash_entry in wrapper.c.
+ * NOTE: __reentrant so that parameters and temperary vairables are placed on the
+ *          stack, ensuring the main application __data variables are not stomped on.
+ * NOTE: __critical to ensure interrupts are disabled. This does mean that interrupt
+ *          such as the timer will be block until flash acccess is complete
+ */
+void flash_entry(uint32_t addr, uint8_t * data, uint32_t length, uint8_t command) __reentrant __critical {
+    // Only allow access from 64KB to 128KB.
+    if ((addr < 0x10000)
+    || (length > 0x10000)
+    || ((addr + length) > 0x20000))
+        return;
+
+    if (command == FLASH_COMMAND_READ) {
+        while (length) {
+            // Fast read.
+            ECINDAR3 = SPI_DEVICE;
+            ECINDAR2 = addr >> 16;
+            ECINDAR1 = addr >> 8;
+            ECINDAR0 = addr;
+
+            *data = ECINDDR;
+
+            addr++;
+            data++;
+            length--;
+        }
+    } else if (command == FLASH_COMMAND_WRITE) {
+        flash_enter_follow_mode();
+
+        while (length) {
+            // Note, this is the slow way to do it, but it's simple and all bytes are written properly.
+            flash_write_enable();
+
+            // Select the device
+            ECINDAR1 = SPI_CHIP_SELECT;
+
+            // Send write command
+            ECINDDR = SPI_WRITE_COMMAND;
+            ECINDDR = addr >> 16;
+            ECINDDR = addr >> 8;
+            ECINDDR = addr;
+
+            ECINDDR = *data;
+
+            addr++;
+            data++;
+            length--;
+
+            // Deselect
+            ECINDAR1 = SPI_CHIP_DESELECT;
+            ECINDDR  = 0x00;
+
+
+            // Wait WIP to be cleared
+            flash_wait();
+        }
+
+        flash_exit_follow_mode();
+    } else if (command == FLASH_COMMAND_ERASE_1K) {
+        flash_enter_follow_mode();
+
+        flash_write_enable();
+
+        // Select the device
+        ECINDAR1 = SPI_CHIP_SELECT;
+
+        // Send erase command
+        ECINDDR = SPI_ERASE_SECTOR_COMMAND;
+        ECINDDR = addr >> 16;
+        ECINDDR = addr >> 8;
+        ECINDDR = addr;
+
+        // Deselect
+        ECINDAR1 = SPI_CHIP_DESELECT;
+        ECINDDR  = 0x00;
+
+        // Wait WIP to be cleared
+        flash_wait();
+
+        flash_exit_follow_mode();
+    }
+}
+
+void flash_enter_follow_mode(void) {
+    // Enter follow mode.
+    ECINDAR3 = SPI_FOLLOW_MODE | SPI_DEVICE;
+    ECINDAR2 = 0xFF;
+    ECINDAR1 = SPI_CHIP_DESELECT;
+    ECINDAR0 = 0x00;
+    ECINDDR = 0x00;
+}
+
+void flash_exit_follow_mode(void) {
+    // Exit follow mode
+    ECINDAR3 = SPI_DEVICE;
+    ECINDAR2 = 0;
+    ECINDAR1 = 0;
+    ECINDAR0 = 0;
+}
+
+void flash_wait(void) {
+    uint8_t status;
+
+    do {
+        // Select the device
+        ECINDAR1 = SPI_CHIP_SELECT;
+
+        // Send command
+        ECINDDR = SPI_READ_STATUS_COMMAND;
+
+        // read status
+        status = ECINDDR;
+
+        // Deselect
+        ECINDAR1 = SPI_CHIP_DESELECT;
+        ECINDDR  = 0x00;
+    } while(status & SPI_STATUS_WIP);
+}
+
+void flash_write_enable(void) {
+    // Select the device
+    ECINDAR1 = SPI_CHIP_SELECT;
+
+    // Send device id command
+    ECINDDR = SPI_WRITE_ENABLE_COMMAND;
+
+    // Deselect
+    ECINDAR1 = SPI_CHIP_DESELECT;
+    ECINDDR  = 0x00;
+}