mtd: cfi_cmdset_0002: Read data 3 times to check write operation status

[Joakim Tjernlund]

On Tue, 2018-04-24 at 14:08 +0000, IKEGAMI Tokunori wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> Hi Jocke-san,
> 
> Thanks for your comment.
> 
> > I find this a bit odd. I am looking at some other erase suspend problems we
> > see on Cypress AMD NOR flash and I have noted that there is more than just DQ6 toggling.
> > Checking DQ5 in combination with DQ6 is one.
> 
>   By the way I have also found only once do_erase_oneblock() was failed by the timeout on the write failure situation.
>   So I thought that the error also can be resolved by the 3 times reading for checking chip_ready().

We have see several times that too many Erase suspend for one block will cause 5.5.2.6 DQ5: Exceeded Timing
Limits
This condition is not checked for nor handled in any way.


> 
> > How did you you arrive at reading 3 times is correct? Is the any documentation
> > supporting this?
> 
>   About the 3 times reading is described by the page 32 on following Cypress S29GLxxxP flash data sheet.
>     <http://www.cypress.com/file/219926/download>

I don't have such info for my chip at page 32, I am looking at S29GL01GS/S29GL512S
S29GL256S/S29GL128S from http://www.cypress.com/file/177976/download

I am looking at chap 5.5.2.5 Reading Toggle Bits DQ6/DQ2

> 
> > All in all, error handling in cmdset0002 is lacking.
> 
>   I have understood as that it is for example FIXME parts for the error case in cfi_cmdset_0002.
>   Is this correct?

Haven't looked at all the FIXME's but I am looking are how erase suspend failure are handled

> 
> Regards,
> Ikegami
> 
> -----Original Message-----
> From: Joakim Tjernlund [mailto:Joakim.Tjernlund at infinera.com]
> Sent: Tuesday, April 24, 2018 8:05 PM
> To: IKEGAMI Tokunori; linux-mtd at lists.infradead.org
> Cc: PACKHAM Chris
> Subject: Re: mtd: cfi_cmdset_0002: Read data 3 times to check write operation status
> 
> On Tue, 2018-04-24 at 05:54 +0000, IKEGAMI Tokunori wrote:
> > 
> > Hi,
> > 
> > Let us consult to change mtd cfi_cmdset_0002 to read data 3 times as below patch.
> > Can we change the mtd cfi_cmdset_0002 driver like this?
> > If any comment or concern please let us know.
> > 
> > From d924822c996b9c0eccc815e5018a0c3ea6077137 Mon Sep 17 00:00:00 2001
> > From: Tokunori Ikegami <ikegami at allied-telesis.co.jp>
> > Date: Tue, 24 Apr 2018 13:26:37 +0900
> > Subject: [PATCH 2/2] mtd: cfi_cmdset_0002: Read data 3 times to check write
> >  operation status
> > 
> > Cypress S29GLxxxP flash is needed to read data 3 times to check DQ6 toggles.
> > Actually the read data is sometimes changed by the 3rd reading.
> > Also this is caused on other flash device also.
> > The flash write failure is possible to be caused by the error.
> > To resolve the issue change the read number of times to 3 from 2.
> 
> Hi
> 
> I find this a bit odd. I am looking at some other erase suspend problems we
> see on Cypress AMD NOR flash and I have noted that there is more than just DQ6 toggling.
> Checking DQ5 in combination with DQ6 is one.
> How did you you arrive at reading 3 times is correct? Is the any documentation
> supporting this?
> 
> All in all, error handling in cmdset0002 is lacking.
> 
>  Jocke
>