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

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Message-ID: <20200429120632.7bce63e6@xps13>
Date:   Wed, 29 Apr 2020 12:06:32 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Christophe Kerello <christophe.kerello@...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

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