* NAND: Verify probe by retrying to checking the results match
@ 2008-04-14 13:16 Ben Dooks
2008-04-14 13:33 ` Artem Bityutskiy
0 siblings, 1 reply; 3+ messages in thread
From: Ben Dooks @ 2008-04-14 13:16 UTC (permalink / raw
To: linux-mtd; +Cc: Ben Dooks
[-- Attachment #1: simtec/simtec-drivers-mtd-nand-doubleprobe.patch --]
[-- Type: text/plain, Size: 1423 bytes --]
With modern systems using bus-hold instead of bus pull-up, it can
often lead to erroneous reporting of NAND devices where there are
none. Do a double probe to ensure that the result we got the first
time is repeatable, and if it is not then return that there is no
chip there.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
--- linux-2.6.24-quilt16.orig/drivers/mtd/nand/nand_base.c
+++ linux-2.6.24-quilt16/drivers/mtd/nand/nand_base.c
@@ -2229,6 +2229,7 @@ static struct nand_flash_dev *nand_get_f
{
struct nand_flash_dev *type = NULL;
int i, dev_id, maf_idx;
+ int tmp_id, tmp_manf;
/* Select the device */
chip->select_chip(mtd, 0);
@@ -2239,6 +2240,22 @@ static struct nand_flash_dev *nand_get_f
/* Read manufacturer and device IDs */
*maf_id = chip->read_byte(mtd);
dev_id = chip->read_byte(mtd);
+
+ /* Try again to make sure. */
+
+ chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
+
+ /* Read manufacturer and device IDs */
+
+ tmp_manf = chip->read_byte(mtd);
+ tmp_id = chip->read_byte(mtd);
+
+ if (tmp_manf != *maf_id || tmp_id != dev_id) {
+ printk(KERN_INFO "%s: second ID read did not match "
+ "%02x,%02x against %02x,%02x\n", __func__,
+ *maf_id, dev_id, tmp_manf, tmp_id);
+ return ERR_PTR(-ENODEV);
+ }
/* Lookup the flash id */
for (i = 0; nand_flash_ids[i].name != NULL; i++) {
--
Ben (ben@fluff.org, http://www.fluff.org/)
'a smiley only costs 4 bytes'
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: NAND: Verify probe by retrying to checking the results match
2008-04-14 13:16 Ben Dooks
@ 2008-04-14 13:33 ` Artem Bityutskiy
0 siblings, 0 replies; 3+ messages in thread
From: Artem Bityutskiy @ 2008-04-14 13:33 UTC (permalink / raw
To: Ben Dooks; +Cc: linux-mtd
On Mon, 2008-04-14 at 14:16 +0100, Ben Dooks wrote:
> With modern systems using bus-hold instead of bus pull-up, it can
> often lead to erroneous reporting of NAND devices where there are
> none. Do a double probe to ensure that the result we got the first
> time is repeatable, and if it is not then return that there is no
> chip there.
>
> Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Could you please put the same comment to the code, to make it easier for
the curious code reader understand why is the second read?
--
Best regards,
Artem Bityutskiy (Битюцкий Артём)
^ permalink raw reply [flat|nested] 3+ messages in thread
* NAND: Verify probe by retrying to checking the results match
@ 2008-04-14 13:58 Ben Dooks
0 siblings, 0 replies; 3+ messages in thread
From: Ben Dooks @ 2008-04-14 13:58 UTC (permalink / raw
To: linux-mtd; +Cc: Ben Dooks
[-- Attachment #1: simtec/simtec-drivers-mtd-nand-doubleprobe.patch --]
[-- Type: text/plain, Size: 1839 bytes --]
With modern systems using bus-hold instead of bus pull-up, it can
often lead to erroneous reporting of NAND devices where there are
none. Do a double probe to ensure that the result we got the first
time is repeatable, and if it is not then return that there is no
chip there.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Index: linux-2.6.24-quilt17/drivers/mtd/nand/nand_base.c
===================================================================
--- linux-2.6.24-quilt17.orig/drivers/mtd/nand/nand_base.c 2008-03-18 10:07:07.000000000 +0000
+++ linux-2.6.24-quilt17/drivers/mtd/nand/nand_base.c 2008-04-14 14:49:06.000000000 +0100
@@ -2229,6 +2229,7 @@ static struct nand_flash_dev *nand_get_f
{
struct nand_flash_dev *type = NULL;
int i, dev_id, maf_idx;
+ int tmp_id, tmp_manf;
/* Select the device */
chip->select_chip(mtd, 0);
@@ -2239,6 +2240,26 @@ static struct nand_flash_dev *nand_get_f
/* Read manufacturer and device IDs */
*maf_id = chip->read_byte(mtd);
dev_id = chip->read_byte(mtd);
+
+ /* Try again to make sure, as some systems the bus-hold or other
+ * interface concerns can cause random data which looks like a
+ * possibly credible NAND flash to appear. If the two results do
+ * not match, ignore the device completely.
+ */
+
+ chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
+
+ /* Read manufacturer and device IDs */
+
+ tmp_manf = chip->read_byte(mtd);
+ tmp_id = chip->read_byte(mtd);
+
+ if (tmp_manf != *maf_id || tmp_id != dev_id) {
+ printk(KERN_INFO "%s: second ID read did not match "
+ "%02x,%02x against %02x,%02x\n", __func__,
+ *maf_id, dev_id, tmp_manf, tmp_id);
+ return ERR_PTR(-ENODEV);
+ }
/* Lookup the flash id */
for (i = 0; nand_flash_ids[i].name != NULL; i++) {
--
Ben (ben@fluff.org, http://www.fluff.org/)
'a smiley only costs 4 bytes'
^ permalink raw reply [flat|nested] 3+ messages in thread
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2008-04-14 13:58 NAND: Verify probe by retrying to checking the results match Ben Dooks
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2008-04-14 13:16 Ben Dooks
2008-04-14 13:33 ` Artem Bityutskiy
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