linux-kernel - Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

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Date:   Fri, 21 Feb 2020 23:36:01 +0800
From:   Xingyu Chen <xingyu.chen@...ogic.com>
To:     Evan Benn <evanbenn@...omium.org>
CC:     Julius Werner <jwerner@...omium.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Rob Herring <robh@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        <linux-watchdog@...r.kernel.org>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Yonghui Yu <yonghui.yu@...ogic.com>
Subject: Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog
 arm,smc-wdt compatible

Hi, Evan

Because the ATF does not define standard wdt index, each vendor defines 
its own index.
So I don't think that the current driver[0] can fully cover my usecases. 
As discussed in your
previous email, the meson wdt driver [1] can use the arm_smccc instead 
of meson_sm_call.

[0]: https://patchwork.kernel.org/patch/11395579/
[1]: https://patchwork.kernel.org/patch/11331271/

Best Regards

On 2020/2/20 14:41, Evan Benn wrote:
> Dear Xingyu,
>
> Could this driver also cover your usecase? I am not familiar with
> meson, but it seems like the meson calls could
> be replaced with arm_smccc calls. Then this driver will cover both
> chips. I am not sure if your firmware is upstream
> somewhere, but this might be adapted;
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405
>
> Thanks
>
>
> On Thu, Feb 20, 2020 at 10:20 AM Guenter Roeck <linux@...ck-us.net> wrote:
>> On Wed, Feb 19, 2020 at 03:04:54PM -0800, Julius Werner wrote:
>>>> You are not the first 'watchdog in firmware accessed via an SMC call'.
>>>> Is there some more detail about what implementation this is? Part of
>>>> TF-A? Defined by some spec (I can dream)?
>>> This is just some random implementation written by me because we
>>> needed one. I would like it to be the new generic implementation, but
>>> it sounds like people here prefer the naming to be MediaTek specific
>>> (at least for now). The other SMC watchdog we're aware of is
>>> imx_sc_wdt but unfortunately that seems to hardcode platform-specific
>> There is one more pending, for Meson SMC.
>>
>> https://patchwork.kernel.org/project/linux-watchdog/list/?series=227733
>>
>> Unfortunately it uses Meson firmware API functions, though it has pretty
>> much the same functionality since those ultimately end up calling
>> arm_smccc_smc().
>>
>> Guenter
>>
>>> details in the interface (at least in the pretimeout SMC) so we can't
>>> just expand that. With this driver I tried to directly wrap the kernel
>>> watchdog interface so it should be platform-agnostic and possible to
>>> expand this driver to other platforms later if desired. The SMC
>>> function ID would still always have to be platform-specific,
>>> unfortunately (but we could pass it in through the device tree), since
>>> the Arm SMC spec doesn't really leave any room for OS-generic SMCs
>>> like this.
> .