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

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Message-ID: <87fuopvwjy.fsf@machinist.wiedmeyer.de>
Date:   Sat, 24 Sep 2016 23:04:49 +0200
From:   Wolfgang Wiedmeyer <wolfgang@...dmeyer.de>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     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,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH] ARM: dts: exynos: Add reboot reason support for Trats2


Krzysztof Kozlowski writes:

> On Thu, Sep 22, 2016 at 08:59:03PM +0200, Wolfgang Wiedmeyer wrote:
>> 
>> 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.
>
> +CC Marek,
>
> Trats2 is working with U-Boot. Just U-Boot. However I never converted S3
> into Trats2 on my own. I always used targets prepared to be "Trats2"
> type. 

It would be awesome to be able to run U-Boot on i9300. Is there a way to
test this by not risking to brick the device, e.g. by booting from the
SD card? Then I could send an updated version of the patch that is
compatible with U-Boot :) 

> Of course kernel is independent to bootloader but in that case you want
> to use a specific interface between kernel and specific bootloader
> type/version. In that case - this should be U-Boot, I think.

I absolutely understand that. Having the patch in mainline doesn't make
much sense if it's not compatible with U-Boot.

Best regards,
Wolfgang

>> >> 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 useful to mention that in commit msg (just the source)...
> however as I wrote above, these values should be for U-Boot, not the
> stock one.
>
> Best regards,
> Krzysztof
>
>> 
>> > 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
>> 
>> 
>> -- 
>> Website: https://fossencdi.org
>> Jabber: wolfgang@...dmeyer.de
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