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From:   Julius Werner <jwerner@chromium.org>
Date:   Fri, 3 Apr 2020 15:56:40 -0700
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Subject: Re: [PATCH v2 2/2] watchdog: Add new arm_smd_wdt watchdog driver
To:     Evan Benn <evanbenn@chromium.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Xingyu Chen <xingyu.chen@amlogic.com>,
        Julius Werner <jwerner@chromium.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Anson Huang <Anson.Huang@nxp.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Leonard Crestez <leonard.crestez@nxp.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Olof Johansson <olof@lixom.net>, Rob Herring <robh@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Vinod Koul <vkoul@kernel.org>, Will Deacon <will@kernel.org>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        LINUX-WATCHDOG <linux-watchdog@vger.kernel.org>
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> +       wdd->info = &smcwd_info;
> +       /* get_timeleft is optional */
> +       if (smcwd_call(SMCWD_GET_TIMELEFT, 0, NULL))

How is this supposed to work? A firmware that implements this call
would return the time left here which may not be 0 (maybe the watchdog
was already primed by the bootloader or whatever), so smcwd_call()
would interpret it as an error.

I think the cleanest solution would be to stick to the same return
codes in a0 and use a1 to report the time left when a0 is
PSCI_SUCCESS. This is more consistent with SMCWD_INIT too.