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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-220d5349226sm98602605ad.24.2025.02.18.22.07.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 22:07:18 -0800 (PST) Sender: Guenter Roeck Message-ID: Date: Tue, 18 Feb 2025 22:07:16 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] driver/aspeed-wdt: fix pretimeout for counting down logic To: Heyi Guo , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org Cc: Wim Van Sebroeck , Joel Stanley , Andrew Jeffery , Eddie James References: <20250218031709.103823-1-guoheyi@linux.alibaba.com> <50ab5a0a-b807-4bd7-bda8-7c6f4bfc76fc@roeck-us.net> <5a33f86d-d82c-4685-8da7-5e623487a40c@linux.alibaba.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2/18/25 19:41, Heyi Guo wrote: > Hi Guenter, > > Thanks for your comments. > > On 2025/2/18 13:33, Guenter Roeck wrote: >> On 2/17/25 19:16, Heyi Guo wrote: >>> Aspeed watchdog uses counting down logic, so the value set to register >>> should be the value of subtracting pretimeout from total timeout. >>> >>> Fixes: 9ec0b7e06835 ("watchdog: aspeed: Enable pre-timeout interrupt") >>> >>> Signed-off-by: Heyi Guo >>> >>> Cc: Wim Van Sebroeck >>> Cc: Guenter Roeck >>> Cc: Joel Stanley >>> Cc: Andrew Jeffery >>> Cc: Eddie James >>> --- >>>   drivers/watchdog/aspeed_wdt.c | 7 +++++++ >>>   1 file changed, 7 insertions(+) >>> >>> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c >>> index b4773a6aaf8c..520d8aba12a5 100644 >>> --- a/drivers/watchdog/aspeed_wdt.c >>> +++ b/drivers/watchdog/aspeed_wdt.c >>> @@ -187,6 +187,13 @@ static int aspeed_wdt_set_pretimeout(struct watchdog_device *wdd, >>>       u32 actual = pretimeout * WDT_RATE_1MHZ; >>>       u32 s = wdt->cfg->irq_shift; >>>       u32 m = wdt->cfg->irq_mask; >>> +    u32 reload = readl(wdt->base + WDT_RELOAD_VALUE); >>> + >> >> It is unusual to use a register value here and not the configured timeout >> value. I would have assumed that pretimeout is compared against wdt->timout, >> not against the register value, and that the multiplication with WDT_RATE_1MHZ >> is done after validation. This needs an explanation. > It was supposed to be a straight-forward way to check if the pretimeout value is supported by the hardware. I can change to wdt->timeout if it is better. > > Further, in the case of wdt->timeout > max_hw_heartbeat_ms, shall we restrict the pretimeout to be larger than wdt->timeout - max_hw_heartbeat_ms  / 2? For the watchdog_kworker works in max_hw_heartbeat_ms  / 2 interval, pretimeout event may be triggered unexpected when watchdog is not pinged in (max_hw_heartbeat_ms - (timeout - pretimeout)). > The kernel internal logic should handle that. If not, it needs to be modified/fixed. >> >>> +    if (actual >= reload) >>> +        return -EINVAL; >>> + >> >> On top of that, you'll also need to explain why watchdog_pretimeout_invalid() >> and with it the validation in watchdog_set_pretimeout() does not work for this >> watchdog and why this extra validation is necessary. > > watchdog_pretimeout_invalid() will return false if wdt->timeout == 0, but we can't determine the hardware pretimeout value if timeout == 0 here. > Sorry, I don't understand what you mean. If watchdog_pretimeout_invalid() returns false if timeout == 0, aspeed_wdt_set_pretimeout() won't be called. Why does that preclude depending on it ? On a side note, I do wonder why the driver accepts a timeout value of 0 seconds. Guenter