From: Wolfgang Grandegger <wg@grandegger•com>
To: Sergei Shtylyov <sshtylyov@ru•mvista.com>
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: Flat device tree definitions for FLASH and MTD partitioning
Date: Thu, 26 Apr 2007 14:59:47 +0200 [thread overview]
Message-ID: <4630A243.8020404@grandegger.com> (raw)
In-Reply-To: <46309CD9.1050403@ru.mvista.com>
Sergei Shtylyov wrote:
> Hello.
>
> Wolfgang Grandegger wrote:
>
>>>>>>>>> are there already some thought or even example code on how to
>>>>>>>>> define Flash memory and MTD partitions in the DTS. This would
>>>>>>>>> avoid the ackward MTD partitioning via static structure or boot
>>>>>>>>> line argument and could be done in a generic way.
>
>>>>>>>> See Documentation/powerpc/booting-without-of.txt and
>>>>>>>> drivers/mtd/physmap_of.c for what's been already done.
>
>>>>>>> I meant drivers/mtd/maps/physmap_of.c
>
>>>>>> I had a closer look to this driver. Unfortunately, it can not
>>>>>> handle yet multiple FLASH banks. This could be achieved with an
>>>>>> additional property "bank_count". What do you think?
>
>>> Please use hyphen, not underscore in property names ("device_type"
>>> seems an only exception from this rule).
>
>> Yes, I know and I also wondered why an "_" is used for the device type.
>
> Ask the OF spec. developers. :-)
>
>>>>> I'm not sure what banks you're talking about -- note that this
>>>>> driver is equivalen in functionality to the plain 'physmap' driver
>>>>> and there's inherited "bank-width" property that handles flash
>>>>> banking.
>
>>>> Yes, I know. Nevertheless the driver cannot handle flash regions
>>>> composed of more than on FLASH bank because we need to probe every
>>>> bank. Search for "BANK" in drivers/mtd/maps" to understand what I mean.
>
>>> Hm, from what I could see, those banks are separate maps registered
>>> to MTD subsys separately.
>>> What's the point of adding a count property when we simply can define
>>> multiple "rom" devices?
>
>> To complete this thread, physmap_of can map _one_ FLASH region
>> composed of one or more FLASH banks. But it currently cannot map more
>> than _one_ FLASH region.
>
> I wodner why?! :-O
I know as well ;-).
>> It would be nice to extend it for multiple FLASH definitions (could
>> code it when time permits).
>
> I'm seeing nothing that prevents it from working now -- it should
> register as much "rom" devices as you supply via the device tree.
OK, I see, for each registered direct-mapped flash resource,
of_physmap_probe() will be called.
Thanks.
Wolfgang.
prev parent reply other threads:[~2007-04-26 12:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-08 11:37 Flat device tree definitions for FLASH and MTD partitioning Wolfgang Grandegger
2007-04-08 12:11 ` Sergei Shtylyov
2007-04-08 12:21 ` Sergei Shtylyov
2007-04-08 12:41 ` Wolfgang Grandegger
2007-04-25 12:55 ` Wolfgang Grandegger
2007-04-25 13:35 ` Sergei Shtylyov
2007-04-25 14:02 ` Wolfgang Grandegger
2007-04-25 14:34 ` Sergei Shtylyov
2007-04-25 18:57 ` Wolfgang Grandegger
2007-04-26 8:21 ` Wolfgang Grandegger
2007-04-26 12:36 ` Sergei Shtylyov
2007-04-26 12:59 ` Wolfgang Grandegger [this message]
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