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5c91fb902d
/* * CPUs often take a performance hit when accessing unaligned memory * locations. The actual performance hit varies, it can be small if the * hardware handles it or large if we have to take an exception and fix * it * in software. * * Since an ethernet header is 14 bytes network drivers often end up * with * the IP header at an unaligned offset. The IP header can be aligned by * shifting the start of the packet by 2 bytes. Drivers should do this * with: * * skb_reserve(NET_IP_ALIGN); * * The downside to this alignment of the IP header is that the DMA is * now * unaligned. On some architectures the cost of an unaligned DMA is high * and this cost outweighs the gains made by aligning the IP header. * * Since this trade off varies between architectures, we allow * NET_IP_ALIGN * to be overridden. */ This new function insl_16 allows to read form 32-bit IO and writes to 16-bit aligned memory. This is useful in above described scenario - In particular with the AXIS AX88180 Gigabit Ethernet MAC. Once the device is in 32-bit mode, reads from the RX FIFO always decrements 4bytes. While on the other side the destination address in SDRAM is always 16-bit aligned. If we use skb_reserve(0) the receive buffer is 32-bit aligned but later we hit a unaligned exception in the IP code. Signed-off-by: Michael Hennerich <michael.hennerich@analog.com> Signed-off-by: Bryan Wu <bryan.wu@analog.com>
98 lines
2.3 KiB
ArmAsm
98 lines
2.3 KiB
ArmAsm
/*
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* File: arch/blackfin/lib/ins.S
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* Based on:
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* Author: Bas Vermeulen <bas@buyways.nl>
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*
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* Created: Tue Mar 22 15:27:24 CEST 2005
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* Description: Implementation of ins{bwl} for BlackFin processors using zero overhead loops.
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*
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* Modified:
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* Copyright 2004-2006 Analog Devices Inc.
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* Copyright (C) 2005 Bas Vermeulen, BuyWays BV <bas@buyways.nl>
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*
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* Bugs: Enter bugs at http://blackfin.uclinux.org/
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see the file COPYING, or write
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* to the Free Software Foundation, Inc.,
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* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/linkage.h>
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#include <asm/blackfin.h>
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.align 2
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ENTRY(_insl)
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P0 = R0; /* P0 = port */
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cli R3;
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P1 = R1; /* P1 = address */
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P2 = R2; /* P2 = count */
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SSYNC;
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LSETUP( .Llong_loop_s, .Llong_loop_e) LC0 = P2;
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.Llong_loop_s: R0 = [P0];
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[P1++] = R0;
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NOP;
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.Llong_loop_e: NOP;
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sti R3;
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RTS;
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ENDPROC(_insl)
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ENTRY(_insw)
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P0 = R0; /* P0 = port */
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cli R3;
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P1 = R1; /* P1 = address */
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P2 = R2; /* P2 = count */
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SSYNC;
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LSETUP( .Lword_loop_s, .Lword_loop_e) LC0 = P2;
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.Lword_loop_s: R0 = W[P0];
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W[P1++] = R0;
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NOP;
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.Lword_loop_e: NOP;
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sti R3;
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RTS;
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ENDPROC(_insw)
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ENTRY(_insb)
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P0 = R0; /* P0 = port */
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cli R3;
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P1 = R1; /* P1 = address */
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P2 = R2; /* P2 = count */
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SSYNC;
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LSETUP( .Lbyte_loop_s, .Lbyte_loop_e) LC0 = P2;
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.Lbyte_loop_s: R0 = B[P0];
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B[P1++] = R0;
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NOP;
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.Lbyte_loop_e: NOP;
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sti R3;
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RTS;
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ENDPROC(_insb)
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ENTRY(_insl_16)
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P0 = R0; /* P0 = port */
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cli R3;
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P1 = R1; /* P1 = address */
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P2 = R2; /* P2 = count */
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SSYNC;
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LSETUP( .Llong16_loop_s, .Llong16_loop_e) LC0 = P2;
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.Llong16_loop_s: R0 = [P0];
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W[P1++] = R0;
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R0 = R0 >> 16;
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W[P1++] = R0;
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NOP;
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.Llong16_loop_e: NOP;
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sti R3;
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RTS;
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ENDPROC(_insl_16)
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