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From: Song, Barry on 20 Jun 2010 22:50


>-----Original Message-----
>From: uclinux-dist-devel-bounces(a)blackfin.uclinux.org
>[mailto:uclinux-dist-devel-bounces(a)blackfin.uclinux.org] On
>Behalf Of Anton Vorontsov
>Sent: Friday, June 18, 2010 9:32 PM
>To: Barry Song
>Cc: David Brownell; Artem Bityutskiy;
>linux-kernel(a)vger.kernel.org; linuxppc-dev(a)ozlabs.org;
>linux-mtd(a)lists.infradead.org;
>uclinux-dist-devel(a)blackfin.uclinux.org; Andrew Morton
>Subject: Re: [Uclinux-dist-devel] [PATCH 1/2] mtd: m25p80:
>Reworkprobing/JEDEC code
>
>On Sat, Jun 12, 2010 at 02:27:12PM +0800, Barry Song wrote:
>> On Wed, Aug 19, 2009 at 5:46 AM, Anton Vorontsov
>> <avorontsov(a)ru.mvista.com> wrote:
>> >
>> > 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
>> This patch caused a problem:
>> even though the external flash doesn't exist, it will still pass the
>> probe() and be registerred into kernel and given the partition table.
>> You may refer to this bug report:
>>
>http://blackfin.uclinux.org/gf/project/uclinux-dist/tracker/?ac
>tion=TrackerItemEdit&tracker_item_id=5975&start=0
>
>Thanks for the report.
>
>There's little we can do about it. Platform code asked us
>to register the device, and JEDEC probing of M25Pxx chips isn't
>reliable (thanks to various vendors that make these JEDEC and
>non-JEDEC variants), so the best thing we can do is to register
>the chip anyway.
>
>OTOH, if the board pulls MISO line up, then the following patch
>should help.
Make sense with pullup to keep the value high while external device
doesn't exist.
>
>If this won't work, we'll have to add some flag to the platform
>data, i.e. to force JEDEC probing, and not trust platform data.

How about we add a non_jedec flag in platform_data, if the flag is 1, we
let the detection pass even though the ID is 0? Otherwise, we need a
valid ID?

>
>Not-yet-Signed-off-by: Anton Vorontsov <cbouatmailru(a)gmail.com>
>---
>
>diff --git a/drivers/mtd/devices/m25p80.c
>b/drivers/mtd/devices/m25p80.c
>index 81e49a9..a307929 100644
>--- a/drivers/mtd/devices/m25p80.c
>+++ b/drivers/mtd/devices/m25p80.c
>@@ -16,6 +16,7 @@
> */
>
> #include <linux/init.h>
>+#include <linux/errno.h>
> #include <linux/module.h>
> #include <linux/device.h>
> #include <linux/interrupt.h>
>@@ -723,7 +724,7 @@ static const struct spi_device_id
>*__devinit jedec_probe(struct spi_device *spi)
> if (tmp < 0) {
> DEBUG(MTD_DEBUG_LEVEL0, "%s: error %d reading
>JEDEC ID\n",
> dev_name(&spi->dev), tmp);
>- return NULL;
>+ return ERR_PTR(tmp);
> }
> jedec = id[0];
> jedec = jedec << 8;
>@@ -737,7 +738,7 @@ static const struct spi_device_id
>*__devinit jedec_probe(struct spi_device *spi)
> * exist for non-JEDEC chips, but for compatibility
>they return ID 0.
> */
> if (jedec == 0)
>- return NULL;
>+ return ERR_PTR(-EEXIST);
>
> ext_jedec = id[3] << 8 | id[4];
>
>@@ -749,7 +750,7 @@ static const struct spi_device_id
>*__devinit jedec_probe(struct spi_device *spi)
> return &m25p_ids[tmp];
> }
> }
>- return NULL;
>+ return ERR_PTR(-ENODEV);
> }
>
>
>@@ -794,9 +795,11 @@ static int __devinit m25p_probe(struct
>spi_device *spi)
> const struct spi_device_id *jid;
>
> jid = jedec_probe(spi);
>- if (!jid) {
>+ if (IS_ERR(jid) && PTR_ERR(jid) == -EEXIST) {
> dev_info(&spi->dev, "non-JEDEC variant of %s\n",
> id->name);
>+ } else if (IS_ERR(jid)) {
>+ return PTR_ERR(jid);
> } else if (jid != id) {
> /*
> * JEDEC knows better, so overwrite
>platform ID. We
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