From: peter@hurleysoftware•com (Peter Hurley)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 2/4] of: DT quirks infrastructure
Date: Fri, 20 Feb 2015 13:09:58 -0500 [thread overview]
Message-ID: <54E77876.9020500@hurleysoftware.com> (raw)
In-Reply-To: <20150220164753.GC22752@roeck-us.net>
Hi Guenter,
On 02/20/2015 11:47 AM, Guenter Roeck wrote:
[...]
> I am open to hearing your suggestions for our use case, where the CPU card with
> the eeprom is manufactured separately from its carier cards.
I think your use case may be more compelling than two flavors of Beaglebone
(one of which is pretty much a dead stick), but it's also less clear what your
design constraints are (not that I really want to know, 'cause I don't).
But the logical extension of this is an N-way dtb that supports unrelated SOCs,
and I think most would agree that's not an acceptable outcome.
My thought was that every design that can afford an EEPROM to probe can afford
a bootloader to select the appropriate dtb, and can afford the extra space
required for multiple dtbs.
I'm not naysaying; I just want to elicit enough information so the community
can make informed decisions.
> I assume you might suggest that manufacturing should (re-)program the EEPROM
> on the CPU card after it was inserted into the carrier.
>
> Problem is though that the CPU card may be inserted into ts carrier outside
> manufacturing, at the final stages of assembly or in product repair. Those
> groups would typically not even have the means to (re-)program the eeprom.
> Besides, manufacturing would, quite understandably, go ballistic if we demand
> that they start programming EEPROMs after insertion into carrier, and no longer
> use pre-programmed EEPROMs.
I agree; that would be The Wrong Way.
> Note that it is not feasible to put the necessary EEPROM onto the carrier
> either. Maybe in a later design. Maybe that makes sense, and we will go along
> that route at some point. However, forcing a specific hardware solution
> due to software limitations, ie lack of ability by core software to handle
> the different carries, seems to be not the right decision to make on an
> OS level.
Agreed; hardware is what it is.
> In the PCI world it has long since been accepted that the world is not perfect.
> The argument here is pretty much equivalent to demanding that PCI drop its
> quirks mechanism, to force the HW manufacturers to finally get it right from
> the beginning. I somehow suspect that this won't happen.
I was thinking back to the introductions of fast DEVSEL# and AGP :(
> Instead of questioning the need for a mechanism such as the one proposed by
> Pantelis, I think our time would be better spent arguing if it is the right
> mechanism and, if not, how it can be improved.
My thoughts exactly. Apologies if something I wrote came across as
"You Shall Not Pass" :)
One issue seems to be the moving target that is the compelling use case(s).
The initial submission implied it was the Beaglebone, which comes with
4GB eMMC/microSD so naturally the argument for space-savings with DTBs doesn't
fly. That has since been clarified so no need to rehash that.
Regards,
Peter Hurley
next prev parent reply other threads:[~2015-02-20 18:09 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-18 14:59 [PATCH 0/4] Device Tree Quirks & the Beaglebone Pantelis Antoniou
2015-02-18 14:59 ` [PATCH 1/4] arm: of: Add a DT quirk method after unflattening Pantelis Antoniou
2015-02-18 14:59 ` [PATCH 2/4] of: DT quirks infrastructure Pantelis Antoniou
2015-02-18 15:41 ` Mark Rutland
2015-02-18 15:53 ` Pantelis Antoniou
2015-02-18 16:32 ` Ludovic Desroches
2015-02-18 16:39 ` Pantelis Antoniou
2015-02-18 16:47 ` Ludovic Desroches
2015-02-18 16:46 ` Matt Porter
2015-02-18 17:31 ` Mark Rutland
2015-02-18 19:32 ` Guenter Roeck
2015-02-19 14:29 ` Pantelis Antoniou
2015-02-19 16:48 ` Frank Rowand
2015-02-19 17:00 ` Pantelis Antoniou
2015-02-19 17:30 ` Frank Rowand
2015-02-19 17:38 ` Pantelis Antoniou
2015-02-19 18:01 ` Maxime Bizon
2015-02-19 18:12 ` Sylvain Rochet
2015-02-19 18:22 ` Maxime Bizon
2015-02-20 14:21 ` Peter Hurley
2015-02-20 14:35 ` Ludovic Desroches
2015-02-20 15:00 ` Peter Hurley
2015-02-20 15:02 ` Pantelis Antoniou
2015-02-20 15:24 ` Peter Hurley
2015-02-20 15:38 ` Pantelis Antoniou
2015-02-20 16:34 ` Peter Hurley
2015-02-20 16:49 ` Pantelis Antoniou
2015-02-20 17:30 ` Rob Herring
2015-02-20 17:37 ` Pantelis Antoniou
2015-02-23 7:00 ` Ludovic Desroches
2015-02-20 14:38 ` Pantelis Antoniou
2015-02-20 16:47 ` Guenter Roeck
2015-02-20 18:09 ` Peter Hurley [this message]
2015-02-20 18:48 ` Guenter Roeck
2015-02-23 7:30 ` Ludovic Desroches
2015-02-20 8:04 ` Ludovic Desroches
2015-02-19 2:08 ` Frank Rowand
2015-02-19 14:41 ` Pantelis Antoniou
2015-02-19 16:40 ` Frank Rowand
2015-02-19 16:51 ` Frank Rowand
2015-02-20 13:23 ` Peter Hurley
2015-02-19 18:01 ` Rob Herring
2015-02-19 18:12 ` Guenter Roeck
2015-02-20 8:16 ` Ludovic Desroches
2015-02-18 14:59 ` [PATCH 3/4] arm: am33xx: DT quirks for am33xx based beaglebone variants Pantelis Antoniou
2015-02-19 18:16 ` Tony Lindgren
2015-02-19 18:28 ` Pantelis Antoniou
2015-02-19 18:36 ` Tony Lindgren
2015-02-19 18:44 ` Pantelis Antoniou
2015-02-23 18:39 ` Peter Hurley
2015-02-23 18:48 ` Pantelis Antoniou
2015-02-19 18:57 ` Guenter Roeck
2015-02-20 16:13 ` Jon Hunter
2015-02-18 14:59 ` [PATCH 4/4] arm: dts: Common Black/White Beaglebone DTS using quirks Pantelis Antoniou
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