CBMEM CONSOLE: Add CBMEM console driver implementation.

The CBMEM console driver saves console output in a CBMEM area, which
then is made available to Linux applications for perusing.

There are some system limitations which need to be worked around
to achieve this goal:

- some console traffic is generated before DRAM is initialized,
  leave alone CBMEM initialized.

- after the RAM based stage starts, a lot of traffic is generated
  before CBMEM is initialized.

As a result, the console log lives in three different places -
the bottom of the cache as RAM space, the CBMEM buffer (where it
is expected to be) and a static buffer used early in the RAM
stage.

When execution starts (in the cache as RAM mode), the console
buffer is allocated at the bottom of the cache as RAM memory
address range. Once DRAM is initialized, the CBMEM structure is
initialized, and then the console buffer contents are copied from
the bottom of the cache as RAM space into the CBMEM area right
before the cache as RAM mode is disabled. The
src/lib/cbmem_console.c:cbmemc_reinit() takes care of the
copying.

At this point the cache as RAM memory is about to be disabled,
but the ROM stage is still going generating console output. To
make sure this output is not lost, cbmemc_reinit() saves the new
buffer address at a fixed location (0x600 was chosen for this),
and the actual "printing" function checks to see if the RAM is
already initialized (the stack is in RAM), and if so, gets the
console buffer pointer from this location instead of using the
cache as RAM address.

When the RAM stage starts, a static buffer is used to store the
console output, as the CBMEM buffer location is not known. Then,
when CBMEM is reinitialized, cbmemc_reinit() again takes care of
the copying.

In case the allocated buffers are not large enough, the excessive
data is dropped, and the copying routine adds some text to the
output buffer to indicate that there has been data lost and how
many characters were dropped.

Change-Id: I8c126e31db6cb2141f7f4f97c5047f39a8db44fc
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: http://review.coreboot.org/719
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

1 files changed, 195 insertions, 0 deletions

diff --git a/src/lib/cbmem_console.c b/src/lib/cbmem_console.c
new file mode 100644
index 0000000000..8cfb33bdf7
--- /dev/null
+++ b/src/lib/cbmem_console.c
@@ -0,0 +1,195 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2011 The ChromiumOS Authors.  All rights reserved.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA
+ */
+
+#include <console/console.h>
+#include <cbmem.h>
+#include <string.h>
+
+/*
+ * Structure describing console buffer. It is overlaid on a flat memory area,
+ * whith buffer_body covering the extent of the memory. Once the buffer is
+ * full, the cursor keeps going but the data is dropped on the floor. This
+ * allows to tell how much data was lost in the process.
+ */
+struct cbmem_console {
+	u32 buffer_size;
+	u32 buffer_cursor;
+	u8  buffer_body[0];
+}  __attribute__ ((__packed__));
+
+#ifdef __PRE_RAM__
+/*
+ * While running from ROM, before DRAM is initialized, some area in cache as
+ * ram space is used for the console buffer storage. The size and location of
+ * the area are defined in the config.
+ */
+#define cbmem_console_p ((struct cbmem_console *)CONFIG_DCACHE_RAM_BASE)
+
+/*
+ * Once DRAM is initialized and the cache as ram mode is disabled, while still
+ * running from ROM, the console buffer in the cache as RAM area becomes
+ * unavailable.
+ *
+ * By this time the console log buffer is already available in
+ * CBMEM. The location at 0x600 is used as the redirect pointer allowing to
+ * find out where the actual console log buffer is.
+ */
+#define CBMEM_CONSOLE_REDIRECT (*((struct cbmem_console **)0x600))
+#else
+
+/*
+ * When running from RAM, a lot of console output is generated before CBMEM is
+ * reinitialized. This static buffer is used to store that output temporarily,
+ * to be concatenated with the CBMEM console buffer contents accumulated
+ * during the ROM stage, once CBMEM becomes available at RAM stage.
+ */
+static u8 static_console[40000];
+static struct cbmem_console *cbmem_console_p;
+#endif
+
+void cbmemc_init(void)
+{
+#ifdef __PRE_RAM__
+	cbmem_console_p->buffer_size = CONFIG_CONSOLE_CAR_BUFFER_SIZE -
+		sizeof(struct cbmem_console);
+#else
+	/*
+	 * Initializing before CBMEM is available, use static buffer to store
+	 * the log.
+	 */
+	cbmem_console_p = (struct cbmem_console *) static_console;
+	cbmem_console_p->buffer_size = sizeof(static_console) -
+		sizeof(struct cbmem_console);
+#endif
+	cbmem_console_p->buffer_cursor = 0;
+}
+
+void cbmemc_tx_byte(unsigned char data)
+{
+	struct cbmem_console *cbm_cons_p = cbmem_console_p;
+	u32 cursor;
+#ifdef __PRE_RAM__
+	/*
+	 * This check allows to tell if the cache as RAM mode has been exited
+	 * or not. If it has been exited, the real memory is being used
+	 * (resulting in the variable on the stack located below
+	 * DCACHE_RAM_BASE), use the redirect pointer to find out where the
+	 * actual console buffer is.
+	 */
+	if ((u32)&cursor < (u32)CONFIG_DCACHE_RAM_BASE)
+		cbm_cons_p = CBMEM_CONSOLE_REDIRECT;
+#endif
+	if (!cbm_cons_p)
+		return;
+
+	cursor = cbm_cons_p->buffer_cursor++;
+	if (cursor < cbm_cons_p->buffer_size)
+		cbm_cons_p->buffer_body[cursor] = data;
+}
+
+/*
+ * Copy the current console buffer (either from the cache as RAM area, or from
+ * the static buffer, pointed at by cbmem_console_p) into the CBMEM console
+ * buffer space (pointed at by new_cons_p), concatenating the copied data with
+ * the CBMEM console buffer contents.
+ *
+ * If there is overflow - add to the destination area a string, reporting the
+ * overflow and the number of dropped charactes.
+ */
+static void copy_console_buffer(struct cbmem_console *new_cons_p)
+{
+	u32 copy_size;
+	u32 cursor = new_cons_p->buffer_cursor;
+	int overflow = cbmem_console_p->buffer_cursor >
+		cbmem_console_p->buffer_size;
+
+	copy_size = overflow ?
+		cbmem_console_p->buffer_size : cbmem_console_p->buffer_cursor;
+
+	memcpy(new_cons_p->buffer_body + cursor,
+	       cbmem_console_p->buffer_body,
+	       copy_size);
+
+	cursor += copy_size;
+
+	if (overflow) {
+		const char loss_str1[] = "\n\n*** Log truncated, ";
+		const char loss_str2[] = " characters dropped. ***\n\n";
+		u32 dropped_chars = cbmem_console_p->buffer_cursor - copy_size;
+
+		/*
+		 * When running from ROM sprintf is not available, a simple
+		 * itoa implementation is used instead.
+		 */
+		int got_first_digit = 0;
+
+		/* Way more than possible number of dropped characters. */
+		u32 mult = 100000;
+
+		strcpy((char *)new_cons_p->buffer_body + cursor, loss_str1);
+		cursor += sizeof(loss_str1) - 1;
+
+		while (mult) {
+			int digit = dropped_chars / mult;
+			if (got_first_digit || digit) {
+				new_cons_p->buffer_body[cursor++] = digit + '0';
+				dropped_chars %= mult;
+				/* Excessive, but keeps it simple */
+				got_first_digit = 1;
+			}
+			mult /= 10;
+		}
+
+		strcpy((char *)new_cons_p->buffer_body + cursor, loss_str2);
+		cursor += sizeof(loss_str2) - 1;
+	}
+	new_cons_p->buffer_cursor = cursor;
+}
+
+void cbmemc_reinit(void)
+{
+	struct cbmem_console *cbm_cons_p;
+
+#ifdef __PRE_RAM__
+	cbm_cons_p = cbmem_add(CBMEM_ID_CONSOLE,
+			       CONFIG_CONSOLE_CBMEM_BUFFER_SIZE);
+	if (!cbm_cons_p) {
+		CBMEM_CONSOLE_REDIRECT = NULL;
+		return;
+	}
+
+	cbm_cons_p->buffer_size = CONFIG_CONSOLE_CBMEM_BUFFER_SIZE -
+		sizeof(struct cbmem_console);
+
+	cbm_cons_p->buffer_cursor = 0;
+
+	copy_console_buffer(cbm_cons_p);
+
+	CBMEM_CONSOLE_REDIRECT = cbm_cons_p;
+#else
+	cbm_cons_p = cbmem_find(CBMEM_ID_CONSOLE);
+
+	if (!cbm_cons_p)
+		return;
+
+	copy_console_buffer(cbm_cons_p);
+
+	cbmem_console_p = cbm_cons_p;
+#endif
+}