linux-kernel - Re: [Uclinux-dist-devel] [PATCH 1/2] mtd: m25p80: Reworkprobing/JEDEC code

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Date:	Mon, 21 Jun 2010 18:31:44 +0800
From:	Barry Song <21cnbao@...il.com>
To:	Anton Vorontsov <cbouatmailru@...il.com>
Cc:	"Song, Barry" <Barry.Song@...log.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Artem Bityutskiy <dedekind1@...il.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	linux-mtd@...ts.infradead.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Uclinux-dist-devel] [PATCH 1/2] mtd: m25p80: Reworkprobing/JEDEC 
	code

On Mon, Jun 21, 2010 at 3:39 PM, Anton Vorontsov <cbouatmailru@...il.com> wrote:
> On Mon, Jun 21, 2010 at 03:22:48PM +0800, Barry Song wrote:
>> On Mon, Jun 21, 2010 at 3:15 PM, Anton Vorontsov <cbouatmailru@...il.com> wrote:
>> > On Mon, Jun 21, 2010 at 11:27:31AM +0800, Barry Song wrote:
>> > [...]
>> >> > 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?
>> >> Here i mean:
>> >
>> > This will break at least OF-enabled platforms (e.g. PowerPC),
>> > they assume that the driver will success for non-JEDEC flashes.
>> > OF platforms don't pass platform data, and even if they did,
>> > device tree doesn't specify if the flash is JEDEC or non-JEDEC.
>> >
>> > Which is why I think that, by default, the driver should
>> > successfully register the flash even if JEDEC probe fails. So,
>> > instead of checking for "!non_jedec", I would recommend
>> > "force_jedec" check.
>>
>> Mike Frysinger suggested to use non_jedec since most devices are
>> standard jedec devices.
>
> Well, on OF platforms most devices that I'm aware of are non-JEDEC.
>
>> Only if non_jedec=1, we let the detection pass
>> if ID is 0.
>
> Then please #ifdef it with CONFIG_OF.
I think the patch has nothing to do with platform. Here SPI Flash is a
peripherals, doesn't depend on any platform. Adding a CONFIG_OF
doesn't make sense very much.
If you think most devices are non-JEDEC, we can change non_JEDEC to
force_JEDEC as you said. But anyway, is that real that most devices
are non_JEDEC?  If not, I think we should change OF platform codes to
fit with this patch.

>
> Thanks,
>
>> >> Index: drivers/mtd/devices/m25p80.c
>> >> ===================================================================
>> >> --- drivers/mtd/devices/m25p80.c      (revision 8927)
>> >> +++ drivers/mtd/devices/m25p80.c      (revision 8929)
>> >> @@ -795,8 +795,13 @@
>> >>
>> >>               jid = jedec_probe(spi);
>> >>               if (!jid) {
>> >> -                     dev_info(&spi->dev, "non-JEDEC variant of %s\n",
>> >> -                              id->name);
>> >> +                     if (!data->non_jedec) {
>> >> +                             dev_err(&spi->dev, "fail to detect%s\n",
>> >> +                                             id->name);
>> >> +                             return -ENODEV;
>> >> +                     } else
>> >> +                             dev_info(&spi->dev, "non-JEDEC variant of %s\n",
>> >> +                                             id->name);
>> >>               } else if (jid != id) {
>> >
>> > --
>> > Anton Vorontsov
>> > email: cbouatmailru@...il.com
>> > irc://irc.freenode.net/bd2
>> >
>
> --
> Anton Vorontsov
> email: cbouatmailru@...il.com
> irc://irc.freenode.net/bd2
>
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