From: Wolfgang Grandegger <wg@grandegger•com>
To: avorontsov@ru•mvista.com
Cc: linuxppc-dev@ozlabs•org,
devicetree-discuss list <devicetree-discuss@ozlabs•org>,
linux-mtd@lists•infradead.org
Subject: Re: [PATCH v3 3/4] powerpc: NAND: FSL UPM: document new bindings
Date: Thu, 26 Mar 2009 23:14:42 +0100 [thread overview]
Message-ID: <49CBFE52.6090706@grandegger.com> (raw)
In-Reply-To: <20090326173302.GA23187@oksana.dev.rtsoft.ru>
Anton Vorontsov wrote:
> On Thu, Mar 26, 2009 at 11:02:06AM -0600, Grant Likely wrote:
> []
>>>> Here is another thought. The binding is describing that address lines
>>>> are used to activate CS lines. Offset for chip access purposes is
>>>> derived from the address line, but it doesn't directly describe the
>>>> hardware. The following may be a better description of the hardware.
>>>>
>>>> fsl,upm-addr-line-cs = <9 10>;
>>> The TQM8548 hardware has some logic connected to the two address lines
>>> allowing to select up to 4 chips with two address lines:
>>>
>>> fsl,upm-addr-line-cs-offsets = <0x0 0x200 0x400 0x600>
>> Ah. I see. This is board specific then. I think it is premature to
>> try and define a generic solution here because it depends on custom
>> board hardware and different boards could use very different logic.
>> The next board could end up doing something completely different. I'd
>> rather start to see trends in multiple boards implementing the same
>> scheme before trying to craft a generic scheme.
>>
>> In other words, this device is not register-level compatible with the
>> fsl,upm-nand device. Give the node a new compatible value
>> (tqc,tqm8548-upm-nand) and add another entry to the of_fun_match table
>> for the new device. Use the .data element in the match table to
>> supply an alternate fun_cmd_ctrl() function for this board (instead of
>> using a property value do decide which fun_cmd_ctrl() behaviour to
>> use). New boards that *do* use the same addressing scheme can claim
>> compatibility with tqc,tqm8548-upm-nand.
>
> I don't like this. :-/
>
> UPM is an universal thing, so there are thousands of ways we can
> connect NAND to the UPM. Of which only ~10 would be sane (others are
> insane, and nobody would do this. If they do, _then_ we'll fall back
> to <board>-upm-nand scheme for a particular board).
Yep.
> I don't see any problem with fsl,upm-addr-line-cs-offsets. It can
> describe any scheme in "addr lines are cs" connection, it's a common
> setup for multi-chip memory, we shouldn't treat it is as something
> extraordinary.
I fully agree. I'm going to provide a patch on monday.
Wolfgang.
next prev parent reply other threads:[~2009-03-26 22:14 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-25 10:08 [PATCH v3 0/4] NAND: Multi-chip support for FSL-UPM for TQM8548 modules Wolfgang Grandegger
2009-03-25 10:08 ` [PATCH v3 1/4] NAND: FSL-UPM: add multi chip support Wolfgang Grandegger
2009-03-25 10:08 ` [PATCH v3 2/4] NAND: FSL-UPM: Add wait flags to support board/chip specific delays Wolfgang Grandegger
2009-03-25 10:08 ` [PATCH v3 3/4] powerpc: NAND: FSL UPM: document new bindings Wolfgang Grandegger
2009-03-25 10:08 ` [PATCH v3 4/4] powerpc/85xx: TQM8548: Update DTS file for multi-chip support Wolfgang Grandegger
2009-03-25 15:11 ` [PATCH v3 3/4] powerpc: NAND: FSL UPM: document new bindings Anton Vorontsov
2009-03-25 17:48 ` Grant Likely
2009-03-25 20:48 ` Wolfgang Grandegger
2009-03-26 5:09 ` Grant Likely
2009-03-26 7:42 ` Wolfgang Grandegger
2009-03-26 14:27 ` Grant Likely
2009-03-26 15:33 ` Wolfgang Grandegger
2009-03-26 16:04 ` Grant Likely
2009-03-26 16:35 ` Wolfgang Grandegger
2009-03-26 17:02 ` Grant Likely
2009-03-26 17:33 ` Anton Vorontsov
2009-03-26 22:14 ` Wolfgang Grandegger [this message]
2009-03-26 23:22 ` Grant Likely
2009-03-26 23:32 ` Anton Vorontsov
2009-03-27 8:07 ` Wolfgang Grandegger
2009-03-25 15:01 ` [PATCH v3 2/4] NAND: FSL-UPM: Add wait flags to support board/chip specific delays Anton Vorontsov
2009-03-25 10:43 ` [PATCH v3 1/4] NAND: FSL-UPM: add multi chip support Singh, Vimal
2009-03-25 10:57 ` Wolfgang Grandegger
2009-03-25 13:31 ` Grant Likely
2009-03-25 13:32 ` Grant Likely
2009-03-25 13:43 ` Wolfgang Grandegger
2009-03-25 17:26 ` Grant Likely
2009-03-25 14:57 ` Anton Vorontsov
2009-03-25 15:25 ` Wolfgang Grandegger
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