Changes for v2: - Removed all bitfield access macros
Signed-off-by: Simon Glass sjg@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