mtd: m25p80: Rework probing/JEDEC code

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=18c6182bae0acca220ed6611f741034d563cd19f
Commit:     18c6182bae0acca220ed6611f741034d563cd19f
Parent:     b34bc037b26e621e5fc13466767e4da110a7b3d3
Author:     Anton Vorontsov <avorontsov at ru.mvista.com>
AuthorDate: Mon Oct 12 20:24:38 2009 +0400
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Mon Nov 30 11:26:15 2009 +0000

    mtd: m25p80: Rework probing/JEDEC code
    
    Previosly the driver always tried JEDEC probing, assuming that non-JEDEC
    chips will return '0'. But truly non-JEDEC chips (like CAT25) won't do
    that, their behaviour on RDID command is undefined, so the driver should
    not call jedec_probe() for these chips.
    
    Also, be less strict on error conditions, don't fail to probe if JEDEC
    found a chip that is different from what platform code told, instead
    just print some warnings and use an information obtained via JEDEC. In
    that case we should not trust partitions any longer, but they might be
    still useful (i.e. they could protect some parts of the chip).
    
    Signed-off-by: Anton Vorontsov <avorontsov at ru.mvista.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/devices/m25p80.c |   69 ++++++++++++++++++++++++-----------------
 1 files changed, 40 insertions(+), 29 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 47486fb..e689285 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -709,6 +709,14 @@ static const struct spi_device_id *__devinit jedec_probe(struct spi_device *spi)
 	jedec = jedec << 8;
 	jedec |= id[2];
 
+	/*
+	 * Some chips (like Numonyx M25P80) have JEDEC and non-JEDEC variants,
+	 * which depend on technology process. Officially RDID command doesn't
+	 * exist for non-JEDEC chips, but for compatibility they return ID 0.
+	 */
+	if (jedec == 0)
+		return NULL;
+
 	ext_jedec = id[3] << 8 | id[4];
 
 	for (tmp = 0; tmp < ARRAY_SIZE(m25p_ids) - 1; tmp++) {
@@ -730,7 +738,7 @@ static const struct spi_device_id *__devinit jedec_probe(struct spi_device *spi)
  */
 static int __devinit m25p_probe(struct spi_device *spi)
 {
-	const struct spi_device_id	*id;
+	const struct spi_device_id	*id = spi_get_device_id(spi);
 	struct flash_platform_data	*data;
 	struct m25p			*flash;
 	struct flash_info		*info;
@@ -743,41 +751,44 @@ static int __devinit m25p_probe(struct spi_device *spi)
 	 */
 	data = spi->dev.platform_data;
 	if (data && data->type) {
+		const struct spi_device_id *plat_id;
+
 		for (i = 0; i < ARRAY_SIZE(m25p_ids) - 1; i++) {
-			id = &m25p_ids[i];
-			info = (void *)m25p_ids[i].driver_data;
-			if (strcmp(data->type, id->name))
+			plat_id = &m25p_ids[i];
+			if (strcmp(data->type, plat_id->name))
 				continue;
 			break;
 		}
 
-		/* unrecognized chip? */
-		if (i == ARRAY_SIZE(m25p_ids) - 1) {
-			DEBUG(MTD_DEBUG_LEVEL0, "%s: unrecognized id %s\n",
-					dev_name(&spi->dev), data->type);
-			info = NULL;
-
-		/* recognized; is that chip really what's there? */
-		} else if (info->jedec_id) {
-			id = jedec_probe(spi);
-
-			if (id != &m25p_ids[i]) {
-				dev_warn(&spi->dev, "found %s, expected %s\n",
-						id ? id->name : "UNKNOWN",
-						m25p_ids[i].name);
-				info = NULL;
-			}
-		}
-	} else {
-		id = jedec_probe(spi);
-		if (!id)
-			id = spi_get_device_id(spi);
-
-		info = (void *)id->driver_data;
+		if (plat_id)
+			id = plat_id;
+		else
+			dev_warn(&spi->dev, "unrecognized id %s\n", data->type);
 	}
 
-	if (!info)
-		return -ENODEV;
+	info = (void *)id->driver_data;
+
+	if (info->jedec_id) {
+		const struct spi_device_id *jid;
+
+		jid = jedec_probe(spi);
+		if (!jid) {
+			dev_info(&spi->dev, "non-JEDEC variant of %s\n",
+				 id->name);
+		} else if (jid != id) {
+			/*
+			 * JEDEC knows better, so overwrite platform ID. We
+			 * can't trust partitions any longer, but we'll let
+			 * mtd apply them anyway, since some partitions may be
+			 * marked read-only, and we don't want to lose that
+			 * information, even if it's not 100% accurate.
+			 */
+			dev_warn(&spi->dev, "found %s, expected %s\n",
+				 jid->name, id->name);
+			id = jid;
+			info = (void *)jid->driver_data;
+		}
+	}
 
 	flash = kzalloc(sizeof *flash, GFP_KERNEL);
 	if (!flash)