Hi Simon, Le 05/07/2011 18:49, Simon Glass a écrit : > Signed-off-by: Simon Glass<s...@chromium.org> > --- > Changes in v2: > - Removed all bitfield access macros
Not sure I follow you: the added lines below do indeed add bitfield access macros, don't they? > 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); > + */ What's the benefit of this over directly specifying a shift and mask value, e.g. #define UART_FBCON_SHIFT 3 and #define UART_FBCON_MASK 0x7 and doing shifts and ANDs? I don't see this as simpler or more intuitive. > +#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 Amicalement, -- Albert. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
