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Subject: Re: [PATCH 3/4] watchdog: add meson secure watchdog driver
To:     Guenter Roeck <linux@roeck-us.net>,
        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>
References: <1570874721-36077-1-git-send-email-xingyu.chen@amlogic.com>
 <1570874721-36077-4-git-send-email-xingyu.chen@amlogic.com>
 <07e8aef0-c991-f212-d500-c5ce77b3dea3@roeck-us.net>
 <51912003-658e-d290-d4db-130808caf6cd@amlogic.com>
 <1c2ac5b1-4ba4-b4e9-8775-b1597d9aae99@roeck-us.net>
From:   Xingyu Chen <xingyu.chen@amlogic.com>
Message-ID: <753ce57b-f271-2d21-7d55-b0014f21b39c@amlogic.com>
Date:   Tue, 15 Oct 2019 13:45:47 +0800
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Hi, Guenter

On 2019/10/14 21:49, Guenter Roeck wrote:
> On 10/14/19 4:42 AM, Xingyu Chen wrote:
>> Hi, Guenter
>> Thanks for your review.
>>
>> On 2019/10/12 22:29, Guenter Roeck wrote:
>>> On 10/12/19 3:05 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         |  16 +++
>>>>   drivers/watchdog/Makefile        |   1 +
>>>>   drivers/watchdog/meson_sec_wdt.c | 205 
>>>> +++++++++++++++++++++++++++++++++++++++
>>>>   3 files changed, 222 insertions(+)
>>>>   create mode 100644 drivers/watchdog/meson_sec_wdt.c
>>>>
>>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>>>> index 58e7c10..e6b0707 100644
>>>> --- a/drivers/watchdog/Kconfig
>>>> +++ b/drivers/watchdog/Kconfig
>>>> @@ -826,6 +826,22 @@ 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 ARCH_MESON || COMPILE_TEST
>>>
>>> Did you try COMPILE_TEST (eg allmodconfig) on, say x86_64 ?
>>> AFAICS the meson sm calls are only available if MESON_SM is
>>> enabled, and that depends on both ARCH_MESON and ARM64_4K_PAGES.
>>> This dependency is not expressed here, and neither is enabled
>>> with COMPILE_TEST.Sorry, I have't done this kind of test before for 
>>> this patchset. There
>> is a kernel build error which related to the current driver when i try 
>> to use allmodconfig with x86. I will fix it by adding "depends on 
>> MESON_SM" in next version.
>>>
>>>> +    select WATCHDOG_CORE
>>>> +    help
>>>> +      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 ATF for the watchdog operation.
>>>> +
>>>> +      Say Y here if watchdog controller on Meson SoCs is located in
>>>> +      secure world.
>>>> +
>>>> +      To compile this driver as a module, choose M here: the
>>>> +      module will be called meson_sec_wdt.
>>>> +
>>>>   config MESON_WATCHDOG
>>>>       tristate "Amlogic Meson SoCs watchdog support"
>>>>       depends on ARCH_MESON || COMPILE_TEST
>>>> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
>>>> index 2ee352b..5e6b73d 100644
>>>> --- a/drivers/watchdog/Makefile
>>>> +++ b/drivers/watchdog/Makefile
>>>> @@ -78,6 +78,7 @@ obj-$(CONFIG_QCOM_WDT) += qcom-wdt.o
>>>>   obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
>>>>   obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
>>>>   obj-$(CONFIG_MESON_GXBB_WATCHDOG) += meson_gxbb_wdt.o
>>>> +obj-$(CONFIG_MESON_SEC_WATCHDOG) += meson_sec_wdt.o
>>>>   obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
>>>>   obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
>>>>   obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
>>>> diff --git a/drivers/watchdog/meson_sec_wdt.c 
>>>> b/drivers/watchdog/meson_sec_wdt.c
>>>> new file mode 100644
>>>> index 00000000..2b5357c
>>>> --- /dev/null
>>>> +++ b/drivers/watchdog/meson_sec_wdt.c
>>>> @@ -0,0 +1,205 @@
>>>> +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
>>>> +/*
>>>> + * Copyright (c) 2019 Amlogic, Inc. All rights reserved.
>>>> + * Author: Xingyu Chen <xingyu.chen@amlogic.com>
>>>> + *
>>>> + */
>>>> +#include <linux/err.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/of.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/types.h>
>>>> +#include <linux/watchdog.h>
>>>> +#include <linux/firmware/meson/meson_sm.h>
>>>> +
>>>> +#define MESON_SIP_WDT_DISABLE        0x1
>>>> +#define MESON_SIP_WDT_ENABLE        0x2
>>>> +#define MESON_SIP_WDT_PING        0x3
>>>> +#define MESON_SIP_WDT_INIT        0x4
>>>> +#define MESON_SIP_WDT_RESETNOW        0x5
>>>> +#define MESON_SIP_WDT_SETTIMEOUT    0x6
>>>> +#define MESON_SIP_WDT_GETTIMELEFT    0x7
>>>> +
>>>> +#define DEFAULT_TIMEOUT            30 /* seconds */
>>>> +
>>>> +/*
>>>> + * Watchdog timer tick is set to 1ms in secfw side, and tick count is
>>>> + * stored in the bit[16-31] of WATCHDOG_CNT register, so the maximum
>>>> + * timeout value is 0xffff ms.
>>>> + */
>>>> +#define MAX_TIMEOUT_MS            0xFFFF
>>>> +
>>>> +struct meson_sec_wdt {
>>>> +    struct watchdog_device wdt_dev;
>>>> +    struct meson_sm_firmware *fw;
>>>> +};
>>>> +
>>>> +static int meson_sec_wdt_start(struct watchdog_device *wdt_dev)
>>>> +{
>>>> +    int ret;
>>>> +    struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
>>>> +
>>>> +    ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
>>>> +                MESON_SIP_WDT_ENABLE, 0, 0, 0, 0); > +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    return 0;
>>>
>>> This is equivalent to
>>>      return ret;
>>> or even
>>>      return meson_sm_call(...);
>>> I will fix it in next version.
>>>> +}
>>>> +
>>>> +static int meson_sec_wdt_stop(struct watchdog_device *wdt_dev)
>>>> +{
>>>> +    int ret;
>>>> +    struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
>>>> +
>>>> +    ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
>>>> +                MESON_SIP_WDT_DISABLE, 0, 0, 0, 0);
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    return 0;
>>>
>>> Same as above.
>> I will fix it in next version.
>>>
>>>> +}
>>>> +
>>>> +static int meson_sec_wdt_ping(struct watchdog_device *wdt_dev)
>>>> +{
>>>> +    struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
>>>> +
>>>> +    meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
>>>> +              MESON_SIP_WDT_PING, 0, 0, 0, 0);
>>>> +
>>>> +    return 0;
>>>
>>> Why ignore errors ?
>> I will fix it as above.
>>>
>>>> +}
>>>> +
>>>> +static int meson_sec_wdt_set_timeout(struct watchdog_device *wdt_dev,
>>>> +                     unsigned int timeout)
>>>> +{
>>>> +    int ret;
>>>> +    struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
>>>> +
>>>> +    wdt_dev->timeout = timeout;
>>>> +    meson_sec_wdt_ping(wdt_dev);
>>>> +
>>>
>>> Unconditionally ? Also, the core does that after setting the 
>>> timeoutIt is used to avoid watchdog timer expire once the timeout is 
>>> updated, 
>> and that the watchdog_ping from core not been invoked. If it is 
>> considered useless, i will remove it.
>>
> 
> As mentioned, the core sends a ping immediately after the update.
Ok, I will remove it in next version, Thanks
> 
>>>
>>>> +    ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
>>>> +                MESON_SIP_WDT_SETTIMEOUT,
>>>> +                wdt_dev->timeout, 0, 0, 0);
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    return 0;
>>>
>>> same as above.
>> I will fix it in next version.
>>>
>>>> +}
>>>> +
>>>> +static unsigned int meson_sec_wdt_get_timeleft(struct 
>>>> watchdog_device *wdt_dev)
>>>> +{
>>>> +    int ret;
>>>> +    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 0;
>>>
>>> Really ? Why ? 0 is most definitely incorrect here.
>> I just want to return a invalid value after I failed to get valid 
>> timeleft. Could you tell me what is corrent value ?
> 
> Why not return the error ?
I will return the error in next version, Thanks for your suggestion.
> 
>>>
>>>> +
>>>> +    return timeleft;
>>>> +}
>>>> +
>>>> +static const struct watchdog_ops meson_sec_wdt_ops = {
>>>> +    .start = meson_sec_wdt_start,
>>>> +    .stop = meson_sec_wdt_stop,
>>>> +    .ping = meson_sec_wdt_ping,
>>>> +    .set_timeout = meson_sec_wdt_set_timeout,
>>>> +    .get_timeleft = meson_sec_wdt_get_timeleft,
>>>> +};
>>>> +
>>>> +static const struct watchdog_info meson_sec_wdt_info = {
>>>> +    .identity = "Meson Secure Watchdog Timer",
>>>> +    .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | 
>>>> WDIOF_MAGICCLOSE,
>>>> +};
>>>> +
>>>> +static int __maybe_unused meson_sec_wdt_resume(struct device *dev)
>>>> +{
>>>> +    struct meson_sec_wdt *data = dev_get_drvdata(dev);
>>>> +
>>>> +    if (watchdog_active(&data->wdt_dev))
>>>> +        meson_sec_wdt_start(&data->wdt_dev);
>>>
>>> No error return ?
>> I will fix it in next version
>>>
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int __maybe_unused meson_sec_wdt_suspend(struct device *dev)
>>>> +{
>>>> +    struct meson_sec_wdt *data = dev_get_drvdata(dev);
>>>> +
>>>> +    if (watchdog_active(&data->wdt_dev))
>>>> +        meson_sec_wdt_stop(&data->wdt_dev);
>>>
>>> No error return ?
>> same as above
>>>
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static const struct dev_pm_ops meson_sec_wdt_pm_ops = {
>>>> +    SET_SYSTEM_SLEEP_PM_OPS(meson_sec_wdt_suspend, 
>>>> meson_sec_wdt_resume)
>>>> +};
>>>> +
>>>> +static const struct of_device_id meson_sec_wdt_dt_ids[] = {
>>>> +     { .compatible = "amlogic,meson-sec-wdt", },
>>>> +     { /* sentinel */ },
>>>> +};
>>>> +MODULE_DEVICE_TABLE(of, meson_sec_wdt_dt_ids);
>>>> +
>>>> +static int meson_sec_wdt_probe(struct platform_device *pdev)
>>>> +{
>>>> +    struct device *dev = &pdev->dev;
>>>> +    struct meson_sec_wdt *data;
>>>> +    struct device_node *sm_np;
>>>> +    int ret;
>>>> +
>>>> +    data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>>>> +    if (!data)
>>>> +        return -ENOMEM;
>>>> +
>>>> +    sm_np = of_parse_phandle(pdev->dev.of_node, "secure-monitor", 0);
>>>> +    if (!sm_np) {
>>>> +        dev_err(&pdev->dev, "no secure-monitor node\n");
>>>> +        return -ENODEV;
>>>
>>> ENODEV is wrong here.
>> I found some drivers use the ENODEV in this case, Eg:
>> - ./watchdog/ts4800_wdt.c -122
>> - ./nvmem/meson-efuse.c   -55
>> ...
>>
>> Could you tell me which error code is more suitable in this case ?
>>
> 
> Yes, I understand, with Millions of LOC to choose from, you will
> find examples for everything somewhere in the Linux kernel.
> That doesn't mean it is a good idea.
> 
> The property is listed as mandatory, so EINVAL would probably be
> most appropriate, unless DT handling proposes a different error code
> in such situations.
Thanks for your help, I will replace ENODEV with EINVAL in next version.
> 
>>>
>>>> +    }
>>>> +
>>>> +    data->fw = meson_sm_get(sm_np);
>>>> +    of_node_put(sm_np);
>>>> +    if (!data->fw)
>>>> +        return -EPROBE_DEFER;
>>>
>>> How do you know ?
>> The fw pointer is static variable which is initialized to NULL. if it 
>> is equal to NULL, and indicate the meson_sm driver is not registered, 
>> then wdt driver use EPROBE_DEFER to defer probe.
>>>
>>>> +
>>>> +    platform_set_drvdata(pdev, data);
>>>> +
>>>> +    data->wdt_dev.parent = dev;
>>>> +    data->wdt_dev.info = &meson_sec_wdt_info;
>>>> +    data->wdt_dev.ops = &meson_sec_wdt_ops;
>>>> +    data->wdt_dev.max_hw_heartbeat_ms = MAX_TIMEOUT_MS;
>>>> +    data->wdt_dev.min_timeout = 1;
>>>> +    data->wdt_dev.timeout = DEFAULT_TIMEOUT;
>>>> +    watchdog_set_drvdata(&data->wdt_dev, data);
>>>> +
>>> No watchdog_init_timeout() ? Any special reason for not supporting
>>> to set the timeout with a devicetree property ?
>> I want to keep consistency with previous meson watchdog driver.
>> as follows:
>> - meson_gxbb_wdt.c
>> - meson_wdt.c
>>
> 
> Yes, again, it is possible to find examples for pretty much everything
> in the linux kernel. But, sure, as you wish.
Thank you again.
> 
> Guenter
> 
> .
>