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mtd: rawnand: use longest matching pattern 

Sometimes the exec_op parser does not choose the optimal pattern if
multiple patterns with optional elements are available. Since the stack
automatically splits operations in multiple exec_op calls, a non-optimal
pattern gets broken up into multiple calls. E.g. an OOB read using the
vf610 driver:
  nand: executing subop:
  nand:     ->CMD      [0x00]
  nand:     ->ADDR     [5 cyc: 00 08 ea 94 02]
  nand:     ->CMD      [0x30]
  nand:     ->WAITRDY  [max 200000 ms]
  nand:       DATA_IN  [64 B]
  nand: executing subop:
  nand:       CMD      [0x00]
  nand:       ADDR     [5 cyc: 00 08 ea 94 02]
  nand:       CMD      [0x30]
  nand:       WAITRDY  [max 200000 ms]
  nand:     ->DATA_IN  [64 B]

However, the vf610 driver has a pattern which can execute the complete
command in a single go...

This patch makes sure that the longest matching pattern is chosen
instead of the first (potentially only partial) match. With this
change the vf610 reads the OOB in a single exec_op call:
  nand: executing subop:
  nand:     ->CMD      [0x00]
  nand:     ->ADDR     [5 cyc: 00 08 c0 1d 00]
  nand:     ->CMD      [0x30]
  nand:     ->WAITRDY  [max 200000 ms]
  nand:     ->DATA_IN  [64 B]

Reported-by: Sascha Hauer <s.hauer@pengutronix.de>
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Tested-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
alistair/sunxi64-5.4-dsi
Stefan Agner 2019-04-19 09:47:17 +02:00 committed by Miquel Raynal
parent f2c7c76c5d
commit 2099920ebe
1 changed files with 37 additions and 13 deletions
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50
drivers/mtd/nand/raw/nand_base.c
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@ -2156,6 +2156,22 @@ static void nand_op_parser_trace(const struct nand_op_parser_ctx *ctx)
}
#endif
static int nand_op_parser_cmp_ctx(const struct nand_op_parser_ctx *a,
const struct nand_op_parser_ctx *b)
{
if (a->subop.ninstrs < b->subop.ninstrs)
return -1;
else if (a->subop.ninstrs > b->subop.ninstrs)
return 1;
if (a->subop.last_instr_end_off < b->subop.last_instr_end_off)
return -1;
else if (a->subop.last_instr_end_off > b->subop.last_instr_end_off)
return 1;
return 0;
}
/**
* nand_op_parser_exec_op - exec_op parser
* @chip: the NAND chip
@ -2190,30 +2206,38 @@ int nand_op_parser_exec_op(struct nand_chip *chip,
unsigned int i;
while (ctx.subop.instrs < op->instrs + op->ninstrs) {
int ret;
const struct nand_op_parser_pattern *pattern;
struct nand_op_parser_ctx best_ctx;
int ret, best_pattern = -1;
for (i = 0; i < parser->npatterns; i++) {
const struct nand_op_parser_pattern *pattern;
struct nand_op_parser_ctx test_ctx = ctx;
pattern = &parser->patterns[i];
if (!nand_op_parser_match_pat(pattern, &ctx))
if (!nand_op_parser_match_pat(pattern, &test_ctx))
continue;
nand_op_parser_trace(&ctx);
if (best_pattern >= 0 &&
nand_op_parser_cmp_ctx(&test_ctx, &best_ctx) <= 0)
continue;
if (check_only)
break;
best_pattern = i;
best_ctx = test_ctx;
}
if (best_pattern < 0) {
pr_debug("->exec_op() parser: pattern not found!\n");
return -ENOTSUPP;
}
ctx = best_ctx;
nand_op_parser_trace(&ctx);
if (!check_only) {
pattern = &parser->patterns[best_pattern];
ret = pattern->exec(chip, &ctx.subop);
if (ret)
return ret;
break;
}
if (i == parser->npatterns) {
pr_debug("->exec_op() parser: pattern not found!\n");
return -ENOTSUPP;
}
/*