linux-kernel - Re: [PATCH v2 06/12] mtd: rawnand: stm32_fmc2: use FMC2_TIMEOUT

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Date:   Wed, 29 Apr 2020 12:13:18 +0200
From:   Christophe Kerello <christophe.kerello@...com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     <richard@....at>, <vigneshr@...com>, <lee.jones@...aro.org>,
        <robh+dt@...nel.org>, <mark.rutland@....com>, <tony@...mide.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <devicetree@...r.kernel.org>, <marex@...x.de>
Subject: Re: [PATCH v2 06/12] mtd: rawnand: stm32_fmc2: use FMC2_TIMEOUT_MS
 for timeouts



On 4/29/20 12:06 PM, Miquel Raynal wrote:
> Hi Christophe,
> 
> Christophe Kerello <christophe.kerello@...com> wrote on Wed, 29 Apr
> 2020 11:41:44 +0200:
> 
>> On 4/29/20 11:35 AM, Miquel Raynal wrote:
>>> Hi Christophe,
>>>
>>> Christophe Kerello <christophe.kerello@...com> wrote on Wed, 29 Apr
>>> 2020 11:27:43 +0200:
>>>    
>>>> Hi Miquèl,
>>>>
>>>> On 4/27/20 8:22 PM, Miquel Raynal wrote:
>>>>> Hi Christophe,
>>>>>
>>>>> Christophe Kerello <christophe.kerello@...com> wrote on Wed, 15 Apr
>>>>> 2020 17:57:30 +0200:
>>>>>     >>>> This patch removes the constant FMC2_TIMEOUT_US.
>>>>>> FMC2_TIMEOUT_MS is set to 5 seconds and this constant is used
>>>>>> each time that we need to wait (except when the timeout value
>>>>>> is set by the framework)
>>>>>>
>>>>>> Signed-off-by: Christophe Kerello <christophe.kerello@...com>
>>>>>> ---
>>>>>>     drivers/mtd/nand/raw/stm32_fmc2_nand.c | 11 +++++------
>>>>>>     1 file changed, 5 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/mtd/nand/raw/stm32_fmc2_nand.c b/drivers/mtd/nand/raw/stm32_fmc2_nand.c
>>>>>> index ab53314..f159c39 100644
>>>>>> --- a/drivers/mtd/nand/raw/stm32_fmc2_nand.c
>>>>>> +++ b/drivers/mtd/nand/raw/stm32_fmc2_nand.c
>>>>>> @@ -37,8 +37,7 @@
>>>>>>     /* Max ECC buffer length */
>>>>>>     #define FMC2_MAX_ECC_BUF_LEN		(FMC2_BCHDSRS_LEN * FMC2_MAX_SG)
>>>>>>     >> -#define FMC2_TIMEOUT_US			1000
>>>>>> -#define FMC2_TIMEOUT_MS			1000
>>>>>> +#define FMC2_TIMEOUT_MS			5000
>>>>>>     >>   /* Timings */
>>>>>>     #define FMC2_THIZ			1
>>>>>> @@ -525,9 +524,9 @@ static int stm32_fmc2_ham_calculate(struct nand_chip *chip, const u8 *data,
>>>>>>     	u32 sr, heccr;
>>>>>>     	int ret;
>>>>>>     >> -	ret = readl_relaxed_poll_timeout(fmc2->io_base + FMC2_SR,
>>>>>> -					 sr, sr & FMC2_SR_NWRF, 10,
>>>>>> -					 FMC2_TIMEOUT_MS);
>>>>>> +	ret = readl_relaxed_poll_timeout_atomic(fmc2->io_base + FMC2_SR,
>>>>>> +						sr, sr & FMC2_SR_NWRF, 1,
>>>>>> +						1000 * FMC2_TIMEOUT_MS);
>>>>>
>>>>> Is the _atomic suffix needed here? If yes it would deserve a separate
>>>>> patch with Fixes/Stable tags.
>>>>>     >>
>>>> I have currently not seen any issues. So, I will remove this modification as we will move to regmap_read_poll_timeout in patch 10.
>>>>   
>>>>>>     	if (ret) {
>>>>>>     		dev_err(fmc2->dev, "ham timeout\n");
>>>>>>     		return ret;
>>>>>> @@ -1315,7 +1314,7 @@ static int stm32_fmc2_waitrdy(struct nand_chip *chip, unsigned long timeout_ms)
>>>>>>     	/* Check if there is no pending requests to the NAND flash */
>>>>>>     	if (readl_relaxed_poll_timeout_atomic(fmc2->io_base + FMC2_SR, sr,
>>>>>>     					      sr & FMC2_SR_NWRF, 1,
>>>>>> -					      FMC2_TIMEOUT_US))
>>>>>> +					      1000 * FMC2_TIMEOUT_MS))
>>>>>>     		dev_warn(fmc2->dev, "Waitrdy timeout\n");
>>>>>>     >>   	/* Wait tWB before R/B# signal is low */
>>>>>
>>>>> You change the timeouts from 1ms to 5s.
>>>>>
>>>>> Maybe 5s is a little bit too much IMHO but we don't really care as this
>>>>> is a timeout. However 1ms is tight. If you are changing this value
>>>>> because it triggers error (eg. when the machine is loaded), then it is
>>>>> a fix and should appear like it.
>>>>>
>>>>> Thanks,
>>>>> Miquèl
>>>>>     >>
>>>> No errors currently happens.
>>>> During our stress tests, in a overloaded system, we have seen that we could be close to 1 second, even if we never met this value.
>>>> So, to be safe, I have set this timeout to 5 seconds.
>>>> As it is just a timeout value, I have not seen any side effect.
>>>> I am using the same timeout constant to avoid to have one timeout per cases.
>>>
>>> Something is wrong in my mind:
>>> You say you observe delays of almost up to 1 second, but the polling
>>> currently happens on 1000 us = 1ms, either you had timeouts or I
>>> misread something?
>>>
>>> Thanks,
>>> Miquèl
>>>    
>>
>> Hi Miquèl,
>>
>> My fault. For this polling, we never met 1 ms.
>> The 1 second observed was on the sequencer when we read/write a page (as it the same timeout value that is used)
> 
> OK I get it. So perhaps you can give these details in the commit log to
> explain why you use 5 seconds instead of one.
> 
> Thanks,
> Miquèl
> 

Hi Miquèl,

A proposal could also be to split this patch:
  - a first patch that is using only one timeout value.
  - a second patch that is increasing the value to 5 seconds.

Regards,
Christophe Kerello.