linux-kernel - Re: [PATCH v2] watchdog: qcom: fine tune the max timeout value calculation

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Date: Tue, 27 Feb 2024 20:36:56 +0530
From: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
To: Guenter Roeck <linux@...ck-us.net>,
        Bjorn Andersson
	<andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Wim Van
 Sebroeck <wim@...ux-watchdog.org>
CC: <linux-arm-msm@...r.kernel.org>, <linux-watchdog@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] watchdog: qcom: fine tune the max timeout value
 calculation



On 2/3/2024 12:07 PM, Kathiravan Thirumoorthy wrote:
> 
> 
> On 1/16/2024 8:32 PM, Guenter Roeck wrote:
>> On 1/16/24 00:22, Kathiravan Thirumoorthy wrote:
>>> To determine the max_timeout value, the below calculation is used.
>>>
>>>     max_timeout = 0x10000000 / clk_rate
>>>
>>> cat 
>>> /sys/devices/platform/soc@...017000.watchdog/watchdog/watchdog0/max_timeout
>>> 8388
>>>
>>> However, this is not valid for all the platforms. IPQ SoCs starting from
>>> IPQ40xx and recent Snapdragron SoCs also has the bark and bite time 
>>> field
>>> length of 20bits, which can hold max up to 32 seconds if the clk_rate is
>>> 32KHz.
>>>
>>> If the user tries to configure the timeout more than 32s, then the value
>>> will be truncated and the actual value will not be reflected in the HW.
>>>
>>> To avoid this, lets add a variable called max_tick_count in the 
>>> device data,
>>> which defines max counter value of the WDT controller. Using this, 
>>> max-timeout
>>> will be calculated in runtime for various WDT contorllers.
>>>
>>> With this change, we get the proper max_timeout as below and restricts
>>> the user from configuring the timeout higher than this.
>>>
>>> cat 
>>> /sys/devices/platform/soc@...017000.watchdog/watchdog/watchdog0/max_timeout
>>> 32
>>>
>>> Signed-off-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
>>
>> Reviewed-by: Guenter Roeck <linux@...ck-us.net>
> 
> 
> Guenter / Will, Can this be picked for v6.9? I don't see this in linux- 
> next yet, so please consider this as a gentle reminder!


Guenter / Will, Gentle Reminder... is this change queued for v6.9?


> 
>>
>>> ---
>>> Changes in v2:
>>> - drop the minimum timeout change from 30s to 32s
>>> - Link to v1: 
>>> https://lore.kernel.org/r/20240111-wdt-v1-1-28c648b3b1f3@quicinc.com
>>> ---
>>>   drivers/watchdog/qcom-wdt.c | 7 +++++--
>>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
>>> index 9e790f0c2096..006f9c61aa64 100644
>>> --- a/drivers/watchdog/qcom-wdt.c
>>> +++ b/drivers/watchdog/qcom-wdt.c
>>> @@ -41,6 +41,7 @@ static const u32 reg_offset_data_kpss[] = {
>>>   struct qcom_wdt_match_data {
>>>       const u32 *offset;
>>>       bool pretimeout;
>>> +    u32 max_tick_count;
>>>   };
>>>   struct qcom_wdt {
>>> @@ -177,11 +178,13 @@ static const struct watchdog_info 
>>> qcom_wdt_pt_info = {
>>>   static const struct qcom_wdt_match_data match_data_apcs_tmr = {
>>>       .offset = reg_offset_data_apcs_tmr,
>>>       .pretimeout = false,
>>> +    .max_tick_count = 0x10000000U,
>>>   };
>>>   static const struct qcom_wdt_match_data match_data_kpss = {
>>>       .offset = reg_offset_data_kpss,
>>>       .pretimeout = true,
>>> +    .max_tick_count = 0xFFFFFU,
>>>   };
>>>   static int qcom_wdt_probe(struct platform_device *pdev)
>>> @@ -236,7 +239,7 @@ static int qcom_wdt_probe(struct platform_device 
>>> *pdev)
>>>        */
>>>       wdt->rate = clk_get_rate(clk);
>>>       if (wdt->rate == 0 ||
>>> -        wdt->rate > 0x10000000U) {
>>> +        wdt->rate > data->max_tick_count) {
>>>           dev_err(dev, "invalid clock rate\n");
>>>           return -EINVAL;
>>>       }
>>> @@ -260,7 +263,7 @@ static int qcom_wdt_probe(struct platform_device 
>>> *pdev)
>>>       wdt->wdd.ops = &qcom_wdt_ops;
>>>       wdt->wdd.min_timeout = 1;
>>> -    wdt->wdd.max_timeout = 0x10000000U / wdt->rate;
>>> +    wdt->wdd.max_timeout = data->max_tick_count / wdt->rate;
>>>       wdt->wdd.parent = dev;
>>>       wdt->layout = data->offset;
>>>
>>> ---
>>> base-commit: 9e21984d62c56a0f6d1fc6f76b646212cfd7fe88
>>> change-id: 20240111-wdt-5bd079ecf14d
>>>
>>> Best regards,
>>
>