linux-kernel - Re: [PATCH 2/4] of: DT quirks infrastructure

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Message-ID: <CAL_JsqLENvqsG+vjK740Aw4yKYONwHB1b-B7mKvE_iAZ1JSdNw@mail.gmail.com>
Date:	Fri, 20 Feb 2015 11:30:12 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	Frank Rowand <frowand.list@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>,
	Koen Kooi <koen@...inion.thruhere.net>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Matt Porter <matt.porter@...aro.org>,
	Guenter Roeck <linux@...ck-us.net>
Cc:	Ludovic Desroches <ludovic.desroches@...el.com>
Subject: Re: [PATCH 2/4] of: DT quirks infrastructure

On Fri, Feb 20, 2015 at 8:35 AM, Ludovic Desroches
<ludovic.desroches@...el.com> wrote:
> On Fri, Feb 20, 2015 at 09:21:38AM -0500, Peter Hurley wrote:
>> On 02/19/2015 12:38 PM, Pantelis Antoniou wrote:
>> >
>> >> On Feb 19, 2015, at 19:30 , Frank Rowand <frowand.list@...il.com> wrote:
>> >>
>> >> On 2/19/2015 9:00 AM, Pantelis Antoniou wrote:
>> >>> Hi Frank,

[...]

>> >>> This is one of those things that the kernel community doesn’t understand which makes people
>> >>> who push product quite mad.
>> >>>
>> >>> Engineering a product is not only about meeting customer spec, in order to turn a profit
>> >>> the whole endeavor must be engineered as well for manufacturability.
>> >>>
>> >>> Yes, you can always manually install files in the bootloader. For 1 board no problem.
>> >>> For 10 doable. For 100 I guess you can hire an extra guy. For 1 million? Guess what,
>> >>> instead of turning a profit you’re losing money if you only have a few cents of profit
>> >>> per unit.
>> >>
>> >> I'm not installing physical components manually.  Why would I be installing software
>> >> manually?  (rhetorical question)
>> >>
>> >
>> > Because on high volume product runs the flash comes preprogrammed and is soldered as is.
>> >
>> > Having a single binary to flash to every revision of the board makes logistics considerably
>> > easier.
>> >
>> > Having to boot and tweak the bootloader settings to select the correct dtb (even if it’s present
>> > on the flash medium) takes time and is error-prone.
>> >
>> > Factory time == money, errors == money.
>> >
>> >>>
>> >>> No knobs to tweak means no knobs to break. And a broken knob can have pretty bad consequences
>> >>> for a few million units.
>> >>
>> >> And you produce a few million units before testing that the first one off the line works?
>> >>
>> >
>> > The first one off the line works. The rest will get some burn in and functional testing if you’re
>> > lucky. In many cases where the product is very cheap it might make financial sense to just ship
>> > as is and deal with recalls, if you’re reasonably happy after a little bit of statistical sampling.
>> >
>> > Hardware is hard :)
>>
>> I'm failing to see how this series improves your manufacturing process at all.
>>
>> 1. Won't you have to provide the factory with different eeprom images for the
>>    White and Black?  You _trust_ them to get that right, or more likely, you
>>    have process control procedures in place so that you don't get 1 million Blacks
>>    flashed with the White eeprom image.
>>
>> 2. The White and Black use different memory technology so it's not as if the
>>    eMMC from the Black will end up on the White SMT line (or vice versa).
>>
>> 3  For that matter, why wouldn't you worry that all the microSD cards intended
>>    for the White were accidentally assembled with the first 50,000 Blacks; at
>>    that point you're losing a lot more than a few cents of profit. And that has
>>    nothing to do with what image you provided.
>>
>
> As you said, we can imagine many reasons to have a failure during the
> production, having several DTB files will increase the risk.

Then package them as a single file. You can even use DT to do that.
See u-boot FIT image.

Rob
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