linux-kernel - Re: [PATCH] ARM: dts: exynos: Add reboot reason support for Trats2

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Date:   Thu, 22 Sep 2016 20:59:03 +0200
From:   Wolfgang Wiedmeyer <wolfgit@...dmeyer.de>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Wolfgang Wiedmeyer <wolfgit@...dmeyer.de>, kgene@...nel.org,
        robh+dt@...nel.org, mark.rutland@....com, linux@...linux.org.uk,
        javier@....samsung.com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: exynos: Add reboot reason support for Trats2


Krzysztof Kozlowski writes:

> On Thu, Sep 22, 2016 at 06:48:35PM +0200, Wolfgang Wiedmeyer wrote:
>> This allows to reboot the device into recovery mode and into the download
>> mode of the bootloader.
>
> Which bootloader? Probably UBoot... or Samsung stock one? Could you put
> that information here?

I'm only working with the stock one. I was under the impression that the
stock bootloader cannot be replaced on a i9300 because there's a
signature check. Is UBoot loaded after the stock one on Trats2 or how
does this work? I didn't find information on that.

>> 
>> Signed-off-by: Wolfgang Wiedmeyer <wolfgit@...dmeyer.de>
>> ---
>>  arch/arm/boot/dts/exynos4412-trats2.dts | 14 ++++++++++++++
>>  arch/arm/boot/dts/exynos4x12.dtsi       |  2 +-
>>  2 files changed, 15 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/arm/boot/dts/exynos4412-trats2.dts b/arch/arm/boot/dts/exynos4412-trats2.dts
>> index 129e973..a38d1e3 100644
>> --- a/arch/arm/boot/dts/exynos4412-trats2.dts
>> +++ b/arch/arm/boot/dts/exynos4412-trats2.dts
>> @@ -1294,3 +1294,17 @@
>>  	vtmu-supply = <&ldo10_reg>;
>>  	status = "okay";
>>  };
>> +
>> +&pmu {
>> +	compatible = "syscon", "simple-mfd";
>> +
>> +	reboot-mode {
>> +		compatible = "syscon-reboot-mode";
>> +		offset = <0x80c>;
>> +
>> +		mode-normal	= <0x12345670>;
>> +		mode-bootloader	= <0x12345671>;
>> +		mode-download	= <0x12345671>;
>> +		mode-recovery	= <0x12345674>;
>
> Hmmm, how did you get these values? Are they already supported?

I only have the vendor source drop as documentation. The magic mode
values [1] and the offset [2] can be found there.

> It would be nice to document them:
> 1. In Documentation/arm/Samsung/Bootloader-interface.txt
> 2. In header. I hate such magic numbers... you could add new header next
>    to existing rockchip one:
>    include/dt-bindings/soc/samsung,boot-mode.h
>    (and update maintainers entry :) )

Thanks for the review! I will do the documentation and update the commit
message.

Best regards,
Wolfgang

[1] https://code.fossencdi.org/kernel_samsung_smdk4412.git/tree/arch/arm/mach-exynos/sec-reboot.c#n65

[2] https://code.fossencdi.org/kernel_samsung_smdk4412.git/tree/arch/arm/mach-exynos/include/mach/regs-pmu.h#n79


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