Re: [PATCHv3] ARM: OMAP2+: am335x-bone*: add DT for BeagleBone Black

From: Jonathan Austin <jonathan.austin@arm.com>
To: Matt Porter <matt.porter@linaro.org>
Cc: Koen Kooi <koen@dominion.thruhere.net>,
	Mark Rutland <Mark.Rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
	Pawel Moll <Pawel.Moll@arm.com>,
	"swarren@wwwdotorg.org" <swarren@wwwdotorg.org>,
	"tony@atomide.com" <tony@atomide.com>,
	"ijc+devicetree@hellion.org.uk" <ijc+devicetree@hellion.org.uk>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"rob.herring@calxeda.com" <rob.herring@calxeda.com>,
	"bcousson@baylibre.com" <bcousson@baylibre.com>,
	"olof@lixom.net" <olof@lixom.net>,
	"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCHv3] ARM: OMAP2+: am335x-bone*: add DT for BeagleBone Black
Date: Mon, 09 Sep 2013 14:51:13 +0100	[thread overview]
Message-ID: <522DD251.2030607@arm.com> (raw)
In-Reply-To: <20130909133059.GD10973@ohporter.com>

Hi Matt,

On 09/09/13 14:31, Matt Porter wrote:
> On Sun, Sep 08, 2013 at 01:12:26PM +0200, Koen Kooi wrote:
>> The BeagleBone Black is basically a regular BeagleBone with eMMC and HDMI added,
>> so create a common dtsi both can use.
>>
>> IMPORTANT: booting the existing am335x-bone.dts will blow up the HDMI transceiver
>> after a dozen boots with an uSD card inserted because LDO will be at 3.3V instead
>> of 1.8.
>>
>> MMC support for AM335x still isn't in, so only the LDO change has been added.
>>
>> Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
>
> Tested-by: Matt Porter <matt.porter@linaro.org>
>
> Works fine for me on tip and 3.11. I did notice a regression in musb (worked
> on 3.11, now failing to probe but this is not related to your new dts as it
> happens on am335x-bone.dts too, assuming merge window volatility). One nit,
> git-am picked up a whitespace error on that extra line at EOF so you should
> trim that out.
>
> Only thing is...for a clear bug like this that will destroy hardware, it
> should be marked Cc: stable@vger.kernel.org to be picked up in stable.
>

If I've understood Koen correctly then what he's saying is that if you 
*were* to use the current (before this patch) am335x-bone.dts on a 
Beagle Bone Black (which would be wrong, as that's not the board you 
have...) then things would break.

I don't see that this patch fixes that - as far as I can see, even after 
the patch, using am335x-bone.dts with a Bone Black will risk the damage?

If so, I don't think this is a 'stable fix' kind of thing, as it doesn't 
actually fix the problem?

Koen - is there a way for a booting kernel to detect which board it is 
on and avoid any potential damage if someone gives it the wrong DT?

Jonny

> -Matt
>
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