console/flashsconsole: Add spi flash console for debugging

If CONSOLE_SPI_FLASH config is enabled, we write the cbmem
messages to the 'CONSOLE' area in FMAP which allows us to grab the
log when we read the flash.

This is useful when you don't have usb debugging, and
UART lines are hard to find. Since a failure to boot would
require a hardware flasher anyways, we can get the log
at the same time.

This feature should only be used when no alternative is
found and only when we can't boot the system, because
excessive writes to the flash is not recommended.

This has been tested on purism/librem13 v2 and librem 15 v3 which
run Intel Skylake hardware. It has not been tested on other archs
or with a driver other than the fast_spi.

Change-Id: I74a297b94f6881d8c27cbe5168f161d8331c3df3
Signed-off-by: Youness Alaoui <youness.alaoui@puri.sm>
Reviewed-on: https://review.coreboot.org/19849
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>

1 files changed, 142 insertions, 0 deletions

diff --git a/src/drivers/spi/flashconsole.c b/src/drivers/spi/flashconsole.c
new file mode 100644
index 0000000000..e73af22951
--- /dev/null
+++ b/src/drivers/spi/flashconsole.c
@@ -0,0 +1,142 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2015 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <arch/early_variables.h>
+#include <region.h>
+#include <boot_device.h>
+#include <fmap.h>
+#include <console/console.h>
+#include <console/flash.h>
+#include <string.h>
+
+#define LINE_BUFFER_SIZE 128
+#define READ_BUFFER_SIZE 0x100
+
+static const struct region_device *g_rdev_ptr CAR_GLOBAL;
+static struct region_device g_rdev CAR_GLOBAL;
+static uint8_t g_line_buffer[LINE_BUFFER_SIZE] CAR_GLOBAL;
+static size_t g_offset CAR_GLOBAL;
+static size_t g_line_offset CAR_GLOBAL;
+
+void flashconsole_init(void)
+{
+	struct region_device *rdev = car_get_var_ptr(&g_rdev);
+	uint8_t buffer[READ_BUFFER_SIZE];
+	size_t size;
+	size_t offset = 0;
+	size_t len = READ_BUFFER_SIZE;
+	size_t i;
+
+	if (fmap_locate_area_as_rdev_rw("CONSOLE", rdev)) {
+		printk(BIOS_INFO, "Can't find 'CONSOLE' area in FMAP\n");
+		return;
+	}
+	size = region_device_sz(rdev);
+
+	/*
+	 * We need to check the region until we find a 0xff indicating
+	 * the end of a previous log write.
+	 * We can't erase the region because one stage would erase the
+	 * data from the previous stage. Also, it looks like doing an
+	 * erase could completely freeze the SPI controller and then
+	 * we can't write anything anymore (apparently might happen if
+	 * the sector is already erased, so we would need to read
+	 * anyways to check if it's all 0xff).
+	 */
+	for (i = 0; i < len && offset < size; ) {
+		// Fill the buffer on first iteration
+		if (i == 0) {
+			len = min(READ_BUFFER_SIZE, size - offset);
+			if (rdev_readat(rdev, buffer, offset, len) != len)
+				return;
+		}
+		if (buffer[i] == 0xff) {
+			offset += i;
+			break;
+		}
+		// If we're done, repeat the process for the next sector
+		if (++i == READ_BUFFER_SIZE) {
+			offset += len;
+			i = 0;
+		}
+	}
+	// Make sure there is still space left on the console
+	if (offset >= size) {
+		printk(BIOS_INFO, "No space left on 'console' region in SPI flash\n");
+		return;
+	}
+
+	car_set_var(g_offset, offset);
+	/* Set g_rdev_ptr last so tx_byte doesn't get executed early */
+	car_set_var(g_rdev_ptr, rdev);
+}
+
+void flashconsole_tx_byte(unsigned char c)
+{
+	const struct region_device *rdev = car_get_var(g_rdev_ptr);
+	uint8_t *line_buffer;
+	size_t offset;
+	size_t len;
+	size_t region_size;
+
+	if (!rdev)
+		return;
+
+	line_buffer = car_get_var_ptr(g_line_buffer);
+	offset = car_get_var(g_offset);
+	len = car_get_var(g_line_offset);
+	region_size = region_device_sz(rdev);
+
+	line_buffer[len++] = c;
+	car_set_var(g_line_offset, len);
+
+	if (len >= LINE_BUFFER_SIZE ||
+		offset + len >= region_size || c == '\n') {
+		flashconsole_tx_flush();
+	}
+}
+
+void flashconsole_tx_flush(void)
+{
+	const struct region_device *rdev = car_get_var(g_rdev_ptr);
+	uint8_t *line_buffer = car_get_var_ptr(g_line_buffer);
+	size_t offset = car_get_var(g_offset);
+	size_t len = car_get_var(g_line_offset);
+	size_t region_size;
+
+	if (!rdev)
+		return;
+
+	/* Prevent any recursive loops in case the spi flash driver
+	 * calls printk (in case of transaction timeout or
+	 * any other error while writing) */
+	car_set_var(g_rdev_ptr, NULL);
+
+	region_size = region_device_sz(rdev);
+	if (offset + len >= region_size)
+		len = region_size - offset;
+
+	if (rdev_writeat(rdev, line_buffer, offset, len) != len)
+		rdev = NULL;
+
+	// If the region is full, stop future write attempts
+	if (offset + len >= region_size)
+		rdev = NULL;
+
+	car_set_var(g_offset, offset + len);
+	car_set_var(g_line_offset, 0);
+
+	car_set_var(g_rdev_ptr, rdev);
+}