jffs2 32-bit access issue

Our board has a PowerPC core inside Xilinx Virtex II Pro FPGA. We have
a Intel Strataflash attached to the FPGA accessed via a 16-bit
interface. Since our interface to the flash part is 16-bit wide and we
do not have any chip selects or other mechanisms to prevent 32-bit
accesses to the part, some of the jffs2 scanning/erasing code fails.
Hence we had to create the patch below to use MTD layer functions (or
simple 8/16 bit access code) to correctly access the part instead of
original jffs2 code that was accessing the flash directly 32-bit wide.
We are would like your opinion as well as find out if this fix (in
some form) needs to go back into jffs2 code for parts that cannot be
accessed 32-bit wide (or need to prevent 32-bit accesses).
we sincerely appreciate your help,
dev team


struct jffs2_summary *s);

 /* These helper functions _must_ increase ofs and also do the
dirty/used space accounting.
 * Returning an error will abort the mount - bad checksums etc.
should just mark the space
@@ -144,7 +144,7 @@
               jffs2_sum_reset_collected(s);

               ret = jffs2_scan_eraseblock(c, jeb,
buf_size?flashbuf:(flashbuf+jeb->offset),
-                                               buf_size, s);
+
buf_size?0:jeb->offset, buf_size, s);

               if (ret < 0)
                       goto out;
@@ -295,8 +295,12 @@

 int jffs2_scan_classify_jeb(struct jffs2_sb_info *c, struct
jffs2_eraseblock *jeb)
 {
+#ifdef CONFIG_ARXXPPC
+  if((jeb->used_size + jeb->unchecked_size) == PAD(c->cleanmarker_size))
+#else
       if ((jeb->used_size + jeb->unchecked_size) ==
PAD(c->cleanmarker_size) && !jeb->dirty_size
           && (!jeb->first_node || !ref_next(jeb->first_node)) )
+#endif /* CONFIG_ARXXPPC */
               return BLK_STATE_CLEANMARKER;

       /* move blocks with max 4 byte dirty space to cleanlist */
@@ -429,13 +433,15 @@
 /* Called with 'buf_size == 0' if buf is in fact a pointer _directly_ into
   the flash, XIP-style */
 static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct
jffs2_eraseblock *jeb,
-                                 unsigned char *buf, uint32_t
buf_size, struct jffs2_summary *s) {
-       struct jffs2_unknown_node *node;
+                                 unsigned char *buf, uint32_t
flash_ofs, uint32_t buf_size,
struct jffs2_summary *s) {
+       struct jffs2_unknown_node nodebuffer;
+  struct jffs2_unknown_node *node = &nodebuffer;
       struct jffs2_unknown_node crcnode;
       uint32_t ofs, prevofs;
       uint32_t hdr_crc, buf_ofs, buf_len;
       int err;
       int noise = 0;
+  struct jffs2_unknown_node *nodeptr;


 #ifdef CONFIG_JFFS2_FS_WRITEBUFFER
@@ -631,7 +637,16 @@
                       buf_ofs = ofs;
               }

-               node = (struct jffs2_unknown_node *)&buf[ofs-buf_ofs];
+    nodeptr = (struct jffs2_unknown_node *)&buf[ofs-buf_ofs];
+    err = jffs2_fill_scan_buf(c, &nodebuffer,
+                              flash_ofs + ofs - buf_ofs,
+                              sizeof(nodebuffer));
+    if(err)
+    {
+      printk("%s:%d error reading flash[%d]\n", __FUNCTION__, __LINE__, err);
+      return err;
+    }
+

               if (*(uint32_t *)(&buf[ofs-buf_ofs]) == 0xffffffff) {
                       uint32_t inbuf_ofs;
@@ -773,7 +788,7 @@
                               buf_ofs = ofs;
                               node = (void *)buf;
                       }
-                       err = jffs2_scan_inode_node(c, jeb, (void
*)node, ofs, s);
+                       err = jffs2_scan_inode_node(c, jeb, (void
*)nodeptr, ofs, s);
                       if (err) return err;
                       ofs += PAD(je32_to_cpu(node->totlen));
                       break;
@@ -789,7 +804,7 @@
                               buf_ofs = ofs;
                               node = (void *)buf;
                       }
-                       err = jffs2_scan_dirent_node(c, jeb, (void
*)node, ofs, s);
+                       err = jffs2_scan_dirent_node(c, jeb, (void
*)nodeptr, ofs, s);
                       if (err) return err;
                       ofs += PAD(je32_to_cpu(node->totlen));
                       break;
@@ -945,10 +960,22 @@
 }

 static int jffs2_scan_inode_node(struct jffs2_sb_info *c, struct
jffs2_eraseblock *jeb,
-                                struct jffs2_raw_inode *ri, uint32_t
ofs, struct jffs2_summary *s)
+                                struct jffs2_raw_inode *ri_unused,
uint32_t ofs, struct jffs2_summary *s)
 {
       struct jffs2_inode_cache *ic;
-       uint32_t crc, ino = je32_to_cpu(ri->ino);
+       uint32_t crc, ino;
+  struct jffs2_raw_inode node;
+  struct jffs2_raw_inode *ri = &node;
+  int err;
+
+  err = jffs2_fill_scan_buf(c, ri, ofs, sizeof(struct jffs2_raw_inode));
+  if(err)
+  {
+    printk("%s:%d err[%d]\n", __FUNCTION__, __LINE__, err);
+    return err;
+  }
+
+  ino = je32_to_cpu(ri->ino);

       D1(printk(KERN_DEBUG "jffs2_scan_inode_node(): Node at 0x%08x\n", ofs));

@@ -1000,15 +1027,24 @@
 }

 static int jffs2_scan_dirent_node(struct jffs2_sb_info *c, struct
jffs2_eraseblock *jeb,
-                                 struct jffs2_raw_dirent *rd,
uint32_t ofs, struct jffs2_summary *s)
+                                 struct jffs2_raw_dirent *rdptr,
uint32_t ofs, struct jffs2_summary *s)
 {
       struct jffs2_full_dirent *fd;
       struct jffs2_inode_cache *ic;
       uint32_t checkedlen;
       uint32_t crc;
       int err;
+  struct jffs2_raw_dirent rdbuf;
+  struct jffs2_raw_dirent *rd = &rdbuf;

       D1(printk(KERN_DEBUG "jffs2_scan_dirent_node(): Node at 0x%08x\n", ofs));
+
+  err = jffs2_fill_scan_buf(c, &rdbuf, ofs, sizeof(rdbuf));
+  if(err)
+  {
+    printk("%s:%d error reading flash[%d]\n", __FUNCTION__, __LINE__, err);
+    return err;
+  }

       /* We don't get here unless the node is still valid, so we don't have to
          mask in the ACCURATE bit any more. */
@@ -1026,7 +1062,11 @@
       pseudo_random += je32_to_cpu(rd->version);

       /* Should never happen. Did. (OLPC trac #4184)*/
+#ifdef CONFIG_ARXXPPC
+  checkedlen = rd->nsize;
+#else
       checkedlen = strnlen(rd->name, rd->nsize);
+#endif /* CONFIG_ARXXPPC */
       if (checkedlen < rd->nsize) {
               printk(KERN_ERR "Dirent at %08x has zeroes in name. Truncating to
%d chars\n",
                      ofs, checkedlen);
@@ -1035,7 +1075,23 @@
       if (!fd) {
               return -ENOMEM;
       }
-       memcpy(&fd->name, rd->name, checkedlen);
+
+  {
+    char* src = rdptr->name;
+    char* dst = &fd->name[0];
+    int i = 0;
+    int j = 0;
+
+    while(i < checkedlen)
+    {
+      dst[i] = src[i];
+      ++i;
+
+      j = 0;
+      while(j++ < 1000);
+    }
+  }
+
       fd->name[checkedlen] = 0;

       crc = crc32(0, fd->name, rd->nsize);


=========== End of Patch ==============================

On Fri, Dec 26, 2008 at 08:36:45AM -0500, ARXX Dev Team wrote:
>Our board has a PowerPC core inside Xilinx Virtex II Pro FPGA. We have
>a Intel Strataflash attached to the FPGA accessed via a 16-bit
>interface. Since our interface to the flash part is 16-bit wide and we
>do not have any chip selects or other mechanisms to prevent 32-bit
>accesses to the part, some of the jffs2 scanning/erasing code fails.
>Hence we had to create the patch below to use MTD layer functions (or
>simple 8/16 bit access code) to correctly access the part instead of
>original jffs2 code that was accessing the flash directly 32-bit wide.
>We are would like your opinion as well as find out if this fix (in
>some form) needs to go back into jffs2 code for parts that cannot be
>accessed 32-bit wide (or need to prevent 32-bit accesses).
>we sincerely appreciate your help,

Why don't you write a custom mapping driver that prevents the 32-bit
accesses at the MTD level?  That seems like a more appropriate place
than sticking it in JFFS2 code, which is supposed to be fairly
hardware independent (with the obvious exception of major flash class
types like NOR, NAND, etc).

josh

That is exactly what we have done. Hence we have added calls to
jffs2_fill_scan_buf(..) in our patch instead of direct access that was
in jffs2 code. Without MTD layer function calls, jffs2 scan/erase
functions fail. As you will see in our code patch, we have accessed
flash data using MTD layer functions (or 16-bit pointers) instead of
32-bit access that exist in jffs2 code.


>
> Why don't you write a custom mapping driver that prevents the 32-bit
> accesses at the MTD level?  That seems like a more appropriate place
> than sticking it in JFFS2 code, which is supposed to be fairly
> hardware independent (with the obvious exception of major flash class
> types like NOR, NAND, etc).
>
> josh
>

On Fri, Dec 26, 2008 at 12:55:08PM -0500, ARXX Dev Team wrote:
>That is exactly what we have done. Hence we have added calls to

No, it isn't.  If it's what you had done, then your mapping driver
would have taken the 32-bit accesses and acted accordingly and
turned them into two 16-bit reads.

>jffs2_fill_scan_buf(..) in our patch instead of direct access that was
>in jffs2 code. Without MTD layer function calls, jffs2 scan/erase
>functions fail. As you will see in our code patch, we have accessed
>flash data using MTD layer functions (or 16-bit pointers) instead of
>32-bit access that exist in jffs2 code.

I can't exactly read your patch because it seems to be corrupted
somehow.  But I'm not sure those hacks are needed at all.

It seems you are trying to force use of the mtd->point methods
and this doesn't really seem to fit with your hardware.  The
mtd->read function should call your driver, which should be able
to determine what to do for your hardware.

josh