[U-Boot] [PATCH v2 1/5] Tegra2: Add macros to calculate bitfield shifts and masks

[Simon Glass]

Changes for v2:
 - Removed all bitfield access macros

Signed-off-by: Simon Glass <sjg at chromium.org>
---
 arch/arm/include/asm/arch-tegra2/bitfield.h |   96 +++++++++++++++++++++++++++
 1 files changed, 96 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/include/asm/arch-tegra2/bitfield.h

diff --git a/arch/arm/include/asm/arch-tegra2/bitfield.h b/arch/arm/include/asm/arch-tegra2/bitfield.h
new file mode 100644
index 0000000..494087c
--- /dev/null
+++ b/arch/arm/include/asm/arch-tegra2/bitfield.h
@@ -0,0 +1,96 @@
+/*
+ * 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
+ */
+
+#ifndef __TEGRA2_BITFIELD_H
+#define __TEGRA2_BITFIELD_H
+
+/*
+ * Basic macros for easily getting mask and shift values for bit fields on
+ * ARM.
+ *
+ * You use these to reliably create shifts and masks from a bit field
+ * definition. Bit fields are defined like this:
+ *
+ * #define NAME_BITS	MSB : LSB
+ *
+ * where MSB is the most significant bit, and LSB the least sig, bit. This
+ * notation is chosen since it is commonly used in CPU / SOC datasheets.
+ *
+ * For example:
+ *
+ * #define UART_FBCON_BITS  5:3		Bit range for the FBCON field
+ *
+ * Note that if you are using a big-endian machine there is no consistent
+ * notion of big numbers, since bit 3 is a different bit depending on whether
+ * the access is 32-bits or 64-bits. For this reason these macros should not
+ * be used as it would probably be too confusing to have to specify your
+ * access width all the time.
+ *
+ * This defines a bit field extending between bits 3 and 5.
+ *
+ * Then in your header file you can set up the shift and mask like this:
+ *
+ *	 #define UART_FBCON_SHIFT	bf_shift(UART_FBCON)
+ *	 #define UART_FBCON_MASK	bf_mask(UART_FBCON)
+ *
+ * Then you can use these macros in your code (there is no bitfield support
+ * in the C file and these macros MUST NOT be used directly in C code).
+ *
+ * To write, overwriting other fields too:
+ *	writel(3 << UART_FBCON_SHIFT, &uart->fbcon);
+ *
+ * To read:
+ *	int fbcon = (readl(&uart->fbcon) & UART_FBCON_MASK) >>
+ *		UART_FBCON_SHIFT;
+ *
+ * To update just this field (for example):
+ *	clrsetbits_le32(&uart->fbcon, UART_FBCON_MASK, 3 << UART_FBCON_SHIFT);
+ */
+
+#include "compiler.h"
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+
+/* Returns the bit number of the LSB */
+#define _LSB(range)	((0 ? range) & 0x1f)
+
+/* Returns the bit number of the MSB */
+#define _MSB(range)	(1 ? range)
+
+/* Returns the width of the bitfield (in bits) */
+#define _BITFIELD_WIDTH(range)	(_MSB(range) - _LSB(range) + 1)
+
+
+/*
+ * Returns the number of bits the bitfield needs to be shifted left to pack it.
+ * This is just the same as the low bit.
+ */
+#define bf_shift(field)		_LSB(field)
+
+/* Returns the unshifted mask for the field (i.e. LSB of mask is bit 0) */
+#define bf_rawmask(field)	((1UL << _BITFIELD_WIDTH(field)) - 1)
+
+/* Returns the mask for a field. Clear these bits to zero the field */
+#define bf_mask(field)		(bf_rawmask(field) << (bf_shift(field)))
+
+#endif /* __BYTE_ORDER == __LITTLE_ENDIAN */
+
+#endif
-- 
1.7.3.1