linux-kernel - Re: [PATCH 2/2] watchdog: mtk_wdt: Add support for MT6735 WDT

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Message-ID: <7b0d5ea4-b3a2-40f2-8762-5a828c2dc485@roeck-us.net>
Date: Wed, 16 Oct 2024 05:51:24 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Yassine Oudjana <yassine.oudjana@...il.com>,
 Wim Van Sebroeck <wim@...ux-watchdog.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: Yassine Oudjana <y.oudjana@...tonmail.com>,
 linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/2] watchdog: mtk_wdt: Add support for MT6735 WDT

On 10/16/24 02:56, AngeloGioacchino Del Regno wrote:
> Il 16/10/24 11:26, Yassine Oudjana ha scritto:
>> On 02/03/2023 6:15 pm, AngeloGioacchino Del Regno wrote:
>>> Il 02/03/23 13:40, Yassine Oudjana ha scritto:
>>>> From: Yassine Oudjana <y.oudjana@...tonmail.com>
>>>>
>>>> Add support for the watchdog timer/top reset generation unit found on MT6735.
>>>> Disable WDT_MODE_IRQ_EN in mtk_wdt_restart in order to make TOPRGU assert
>>>> the SYSRST pin instead of issuing an IRQ. This change may be needed in other
>>>> SoCs as well.
>>>>
>>>> Signed-off-by: Yassine Oudjana <y.oudjana@...tonmail.com>
>>>> ---
>>>>   drivers/watchdog/mtk_wdt.c | 12 ++++++++++++
>>>>   1 file changed, 12 insertions(+)
>>>>
>>>> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
>>>> index a9c437598e7e..5a7a7b2b3727 100644
>>>> --- a/drivers/watchdog/mtk_wdt.c
>>>> +++ b/drivers/watchdog/mtk_wdt.c
>>>> @@ -10,6 +10,7 @@
>>>>    */
>>>>   #include <dt-bindings/reset/mt2712-resets.h>
>>>> +#include <dt-bindings/reset/mediatek,mt6735-wdt.h>
>>>>   #include <dt-bindings/reset/mediatek,mt6795-resets.h>
>>>>   #include <dt-bindings/reset/mt7986-resets.h>
>>>>   #include <dt-bindings/reset/mt8183-resets.h>
>>>> @@ -82,6 +83,10 @@ static const struct mtk_wdt_data mt2712_data = {
>>>>       .toprgu_sw_rst_num = MT2712_TOPRGU_SW_RST_NUM,
>>>>   };
>>>> +static const struct mtk_wdt_data mt6735_data = {
>>>> +    .toprgu_sw_rst_num = MT6735_TOPRGU_RST_NUM,
>>>> +};
>>>> +
>>>>   static const struct mtk_wdt_data mt6795_data = {
>>>>       .toprgu_sw_rst_num = MT6795_TOPRGU_SW_RST_NUM,
>>>>   };
>>>> @@ -187,9 +192,15 @@ static int mtk_wdt_restart(struct watchdog_device *wdt_dev,
>>>>   {
>>>>       struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdt_dev);
>>>>       void __iomem *wdt_base;
>>>> +    u32 reg;
>>>>       wdt_base = mtk_wdt->wdt_base;
>>>> +    /* Enable reset in order to issue a system reset instead of an IRQ */
>>>> +    reg = readl(wdt_base + WDT_MODE);
>>>> +    reg &= ~WDT_MODE_IRQ_EN;
>>>> +    writel(reg | WDT_MODE_KEY, wdt_base + WDT_MODE);
>>>
>>> This is unnecessary and already done in mtk_wdt_start().
>>> If you think you *require* this snippet, you most likely misconfigured the
>>> devicetree node for your device :-)
>>
>> Ok so mtk_wdt_start is never called.
> 
> mtk_wdt_init() says
> 
>      if (readl(wdt_base + WDT_MODE) & WDT_MODE_EN) {
>          set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
>          mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
>      }
> 
> Your bootloader starts the watchdog. This driver will set WDOG_HW_RUNNING and
> will hence prevent calling the .start() callback - that's why.
> 

FWIW, if the bootloader _doesn't_ start the watchdog, and the watchdog device
is never opened, the restart handler has to start the watchdog.

Guenter