From: Guenter Roeck <linux@roeck-us.net>
To: Xingyu Chen <xingyu.chen@amlogic.com>,
Wim Van Sebroeck <wim@linux-watchdog.org>,
Kevin Hilman <khilman@baylibre.com>,
Neil Armstrong <narmstrong@baylibre.com>
Cc: Rob Herring <robh+dt@kernel.org>,
Jerome Brunet <jbrunet@baylibre.com>,
Qianggui Song <qianggui.song@amlogic.com>,
Jianxin Pan <jianxin.pan@amlogic.com>,
Jian Hu <jian.hu@amlogic.com>,
linux-watchdog@vger.kernel.org,
linux-amlogic@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] watchdog: add meson secure watchdog driver
Date: Mon, 21 Oct 2019 06:38:00 -0700 [thread overview]
Message-ID: <bd5ed275-4ae4-4163-b585-23fbead9833f@roeck-us.net> (raw)
In-Reply-To: <bfc892af-1cd3-1437-75b2-5ba2b7913284@amlogic.com>
On 10/21/19 1:03 AM, Xingyu Chen wrote:
> Hi, Guenter
>
> On 2019/10/21 0:56, Guenter Roeck wrote:
>> On 10/18/19 1:33 AM, Xingyu Chen wrote:
>>> The watchdog controller on the Meson-A/C series SoCs is moved to secure
>>> world, watchdog operation needs to be done in secure EL3 mode via ATF,
>>> Non-secure world can call SMC instruction to trap to AFT for watchdog
>>> operation.
>>>
>>> Signed-off-by: Xingyu Chen <xingyu.chen@amlogic.com>
>>> ---
>>> drivers/watchdog/Kconfig | 17 ++++
>>> drivers/watchdog/Makefile | 1 +
>>> drivers/watchdog/meson_sec_wdt.c | 187 +++++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 205 insertions(+)
>>> create mode 100644 drivers/watchdog/meson_sec_wdt.c
>>>
>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>>> index 58e7c10..e84be42 100644
>>> --- a/drivers/watchdog/Kconfig
>>> +++ b/drivers/watchdog/Kconfig
>>> @@ -826,6 +826,23 @@ config MESON_GXBB_WATCHDOG
>>> To compile this driver as a module, choose M here: the
>>> module will be called meson_gxbb_wdt.
>>> +config MESON_SEC_WATCHDOG
>>> + tristate "Amlogic Meson Secure watchdog support"
>>> + depends on MESON_SM
>>> + depends on ARCH_MESON || COMPILE_TEST
>>
>> This dependency is pointless. MESON_SM already depends on ARCH_MESON,
>> thus specifying "COMPILE_TEST" here adds no value but only
>> creates confusion.
> Thanks for your analysis, perhaps i should remove the line below.
> - depends on ARCH_MESON || COMPILE_TEST
>
> Is it ok to modify code above like this ?
Yes.
[ ... ]
>>> +static unsigned int meson_sec_wdt_get_timeleft(struct watchdog_device *wdt_dev)
>>> +{
>>> + int ret;
>>> + unsigned int timeleft;
>>> + struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
>>> +
>>> + ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, &timeleft,
>>> + MESON_SIP_WDT_GETTIMELEFT, 0, 0, 0, 0);
>>> +
>>> + if (ret)
>>> + return ret;
>>
>> Meh, that doesn't work. I just realized that the return type is unsigned,
>> so returning a negative error code is pointless. Guess we'll have to
>> live with returning 0 in this case after all. I wonder if we should
>> fix the API and return an integer (with negative error code), but that
>> is a different question.
> Thanks for your review.
>
> IMO, if returning an integer, and the value which copy to user buf should be formatted with %d instead of %u (see timeleft_show), it will cause the max value of timeleft is reduced from 4294967295 to 2147483647. but i'am not sure whether it will bring risk.
Not that it matters right now, but I don't think that limiting 'timeleft'
reporting to 2147483647 seconds, or ~68 years, would cause any risk.
It would just be a large patch changing several drivers all at once,
that is all.
>
> So i also think returning 0 may be better in this case.
Yes, please do that.
Thanks,
Guenter
next prev parent reply other threads:[~2019-10-21 13:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 8:33 [PATCH v2 0/4] add meson secure watchdog driver Xingyu Chen
2019-10-18 8:33 ` [PATCH v2 1/4] firmware: meson_sm: add new SMC ID support for accessing secure watchdog Xingyu Chen
2019-10-18 8:33 ` [PATCH v2 2/4] dt-bindings: watchdog: add new binding for meson " Xingyu Chen
2019-10-18 8:33 ` [PATCH v2 3/4] watchdog: add meson secure watchdog driver Xingyu Chen
2019-10-20 16:56 ` Guenter Roeck
2019-10-21 8:03 ` Xingyu Chen
2019-10-21 13:38 ` Guenter Roeck [this message]
2019-10-22 5:49 ` Xingyu Chen
2019-10-18 8:33 ` [PATCH v2 4/4] arm64: dts: a1: add secure watchdog controller Xingyu Chen
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