linux-kernel - Re: Watchdog reset trigger for eMMC

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Date:	Tue, 3 May 2016 08:05:43 +0530
From:	Anand Moon <linux.amoon@...il.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	Krzysztof Kozłowski <k.kozlowski@...sung.com>,
	Javier Martinez Canillas <javier@....samsung.com>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Watchdog reset trigger for eMMC

Hi Marek

On 2 May 2016 at 11:57, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
> Hi Anand
>
>
> On 2016-04-30 08:06, Anand Moon wrote:
>>
>> Hi All,
>>
>> Using microSD card when I try to write into /dev/watchdog device
>> it triggers reboot of the board after timer expires.
>>
>> -----------------------------------------------------------------------------------------------
>> root@...oidxu4l:~# echo 3 > /dev/watchdog
>> [ 1659.021844] watchdog: watchdog0: watchdog did not stop!
>> root@...oidxu4l:~#
>> root@...oidxu4l:~#
>> root@...oidxu4l:~#
>> root@...oidxu4l:~#
>> root@...oidxu4l:~#
>>
>> U-Boot 2016.03-00665-g563d8d9-dirty (Apr 04 2016 - 22:27:07 +0930) for
>> ODROID-XU
>>                  3
>>
>> CPU:   Exynos5422 @ 800 MHz
>> Model: Odroid XU3 based on EXYNOS5422
>> Board: Odroid XU3 based on EXYNOS5422
>> Type:  xu4
>> DRAM:  2 GiB
>>
>> -----------------------------------------------------------------------------------------------
>> But when I try this on eMMC it just freezes.
>> I know we have to set and unset gpio pin (SD_0.RST) to trigger reset
>> before reboot.
>>
>> -----------------------------------------------------------------------------------------------
>> root@...oidxu4e:~# echo 4 > /dev/watchdog
>> [  639.192617] [c3] watchdog watchdog0: watchdog did not stop!
>> root@...oidxu4e:~#
>> root@...oidxu4e:~#
>> root@...oidxu4e:~#
>>
>> -----------------------------------------------------------------------------------------------
>> I would like to know what is way board reset after watchdog reset after
>> timeout.
>
>
> In my opinion hw watchdog reset is non-functional on Odroid U3/XU3/XU4
> boards due to
> hardware design (eMMC reset line triggered from software). I see no way to
> workaround
> this issue in the software.
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>

Yes It's difficult to reset eMMC card.
Thanks for clarification.

Best Regards
-Anand Moon