fdt: Add decode functions for UARTs

The fdt_decode library will help drivers access the FDT. This first
starting point implements functions to access information about the console
UART.

BUG=chromium-os:11623
TEST=build and boot U-Boot on Seaboard

Change-Id: I7ff7e5c1d9c38a6301d02d38fb4b993306ca18bd
Reviewed-on: http://gerrit.chromium.org/gerrit/954
Tested-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 92 insertions, 0 deletions

diff --git a/include/fdt_decode.h b/include/fdt_decode.h
new file mode 100644
index 0000000000..b93bf3ad62
--- /dev/null
+++ b/include/fdt_decode.h
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2011 The Chromium OS Authors.
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * 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., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+
+/*
+ * This file contains convenience functions for decoding useful and
+ * enlightening information from FDTs. It is intended to be used by device
+ * drivers and board-specific code within U-Boot. It aims to reduce the
+ * amount of FDT munging required within U-Boot itself, so that driver code
+ * changes to support FDT are minimized.
+ */
+
+/* A typedef for a physical address. We should move it to a generic place */
+#ifdef CONFIG_PHYS_64BIT
+typedef u64 addr_t;
+#define ADDR_T_NONE (-1ULL)
+#define addr_to_cpu(reg) be64_to_cpu(reg)
+#else
+typedef u32 addr_t;
+#define ADDR_T_NONE (-1U)
+#define addr_to_cpu(reg) be32_to_cpu(reg)
+#endif
+
+/* Information obtained about a UART from the FDT */
+struct fdt_uart {
+	addr_t reg;	/* address of registers in physical memory */
+	int id;		/* id or port number (numbered from 0, default -1) */
+	int reg_shift;	/* each register is (1 << reg_shift) apart */
+	int baudrate;	/* baud rate, will be gd->baudrate if not defined */
+	int clock_freq;	/* clock frequency, -1 if not provided */
+	int multiplier;	/* divisor multiplier, default 16 */
+	int divisor;	/* baud rate divisor, default calculated */
+	int enabled;	/* 1 to enable, 0 to disable */
+	int interrupt;	/* interrupt line */
+	int silent;	/* 1 for silent UART (supresses output by default) */
+};
+
+/**
+ * Return information from the FDT about the console UART. This looks for
+ * an alias node called 'console' which must point to a UART. It then reads
+ * out the following attributes:
+ *
+ *	reg
+ *	port
+ *	clock-frequency
+ *	reg-shift (default 2)
+ *	baudrate (default 115200)
+ *	multiplier (default 16)
+ *	divisor (calculated by default)
+ *	enabled (default 1)
+ *	interrupts (returns first in interrupt list, -1 if none)
+ *	silent (default 0)
+ *
+ * The divisor calculation is performed by calling
+ * fdt_decode_uart_calc_divisor() automatically once the information is
+ * available. Therefore callers should be able to simply use the ->divisor
+ * field as their baud rate divisor.
+ *
+ * @param blob	FDT blob to use
+ * @param uart	struct to use to return information
+ * @param default_baudrate  Baud rate to use if none defined in FDT
+ * @return 0 on success, -ve on error, in which case uart is unchanged
+ */
+int fdt_decode_uart_console(const void *blob, struct fdt_uart *uart,
+		int default_baudrate);
+
+/**
+ * Calculate the divisor to use for the uart. This is done based on the
+ * formula (uart clock / (baudrate * multiplier). The divisor is updated
+ * in the uart structure ready for use.
+ *
+ * @param uart	uart structure to examine and update
+ */
+void fdt_decode_uart_calc_divisor(struct fdt_uart *uart);