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[PATCH] [RFC] r4k_dma_cache_wback_inv function fails when size=0...

To: linux-mips <linux-mips@linux-mips.org>
Subject: [PATCH] [RFC] r4k_dma_cache_wback_inv function fails when size=0...
From: "Steven J. Hill" <sjhill@realitydiluted.com>
Date: Mon, 15 Mar 2004 12:08:48 -0500
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040122 Debian/1.6-1
Greetings.

The 'r4k_dma_cache_wback_inv' function will fail when the requested
size equals 0 AND when the address is a multiple of the line size. I
discovered this bug while using the National Semiconductor DP8381x
series PCI ethernet driver. I have attached a test program showing
the bug as well as a patch for comment. Okay to apply?

-Steve
/*
 * Test program for faulty 'r4k_dma_cache_wback_inv' routine where
 * calculated end address can be incorrect when the size = 0.
 *
 * Copyright (C) 2004 TimeSys Corp.
 *                    S. James Hill (James.Hill@timesys.com)
 *                                  (sjhill@realitydiluted.com)
 *
 *  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 SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 *  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 *  OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 *  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 *  TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 *  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *  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.,
 *  675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <stdio.h>

int main (void)
{
        unsigned long addr, a, end;
        unsigned int size, line_size;

        /*
         * Choose an arbitrary test start address and ending address
         * (not the calculated end address).
         */
        for (addr = 0x803e4000; addr < 0x803e8000; addr+=4)
        {
                /*
                 * We assume cache line sizes are always a multiple
                 * of 16 bytes.
                 */
                line_size = 16;
                //line_size = 32;
                {
                        /*
                         * We try all 4-byte aligned sizes up to
                         * the size of a page.
                         */
                        for (size = 0; size < 4096; size+=4)
                        {
                                a = addr & ~(line_size - 1);
                                end = (addr + size - 1) & ~(line_size - 1);
                                if (end < a)
                                        printf("FAIL: a=0x%08lx, end=0x%08lx,"
                                                "line_size=%i, size=%i\n",
                                                a, end, line_size, size);
                        }
                }
        }

        return 0;
}
Index: c-r4k.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/mm/c-r4k.c,v
retrieving revision 1.3.2.67
diff -d -u -r1.3.2.67 c-r4k.c
--- c-r4k.c     5 Mar 2004 02:47:11 -0000       1.3.2.67
+++ c-r4k.c     15 Mar 2004 17:03:29 -0000
@@ -482,7 +482,7 @@
                }
 
                a = addr & ~(sc_lsize - 1);
-               end = (addr + size - 1) & ~(sc_lsize - 1);
+               end = (addr + size + sc_lsize - 1) & ~(sc_lsize - 1);
                while (1) {
                        flush_scache_line(a);   /* Hit_Writeback_Inv_SD */
                        if (a == end)
@@ -504,7 +504,7 @@
 
                R4600_HIT_CACHEOP_WAR_IMPL;
                a = addr & ~(dc_lsize - 1);
-               end = (addr + size - 1) & ~(dc_lsize - 1);
+               end = (addr + size + dc_lsize - 1) & ~(dc_lsize - 1);
                while (1) {
                        flush_dcache_line(a);   /* Hit_Writeback_Inv_D */
                        if (a == end)
@@ -529,7 +529,7 @@
                }
 
                a = addr & ~(sc_lsize - 1);
-               end = (addr + size - 1) & ~(sc_lsize - 1);
+               end = (addr + size + sc_lsize - 1) & ~(sc_lsize - 1);
                while (1) {
                        flush_scache_line(a);   /* Hit_Writeback_Inv_SD */
                        if (a == end)
@@ -546,7 +546,7 @@
 
                R4600_HIT_CACHEOP_WAR_IMPL;
                a = addr & ~(dc_lsize - 1);
-               end = (addr + size - 1) & ~(dc_lsize - 1);
+               end = (addr + size + dc_lsize - 1) & ~(dc_lsize - 1);
                while (1) {
                        flush_dcache_line(a);   /* Hit_Writeback_Inv_D */
                        if (a == end)
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