linux-kernel - Re: [PATCH] mtd: rawnand: qcom: update last code word register

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Date:   Wed, 24 Feb 2021 07:48:50 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     mdalam@...eaurora.org
Cc:     mani@...nel.org, boris.brezillon@...labora.com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        sricharan@...eaurora.org, mdalam=codeaurora.org@...eaurora.org
Subject: Re: [PATCH] mtd: rawnand: qcom: update last code word register

Hello,

mdalam@...eaurora.org wrote on Wed, 24 Feb 2021 10:09:48 +0530:

> On 2021-02-24 01:13, mdalam@...eaurora.org wrote:
> > On 2021-02-23 22:04, Miquel Raynal wrote:  
> >> Hello,  
> >> >> Md Sadre Alam <mdalam@...eaurora.org> wrote on Tue, 23 Feb 2021  
> >> 01:34:27 +0530:  
> >> >>> From QPIC version 2.0 onwards new register got added to read last  
> >> >>                                a new  
> >> >>> codeword. This change will add the READ_LOCATION_LAST_CW_n register.  
> >> >>             Add support for this READ_LOCATION_LAST_CW_n register.  
> >> >>> >>> For first three code word READ_LOCATION_n register will be  
> >>> use.For last code word READ_LOCATION_LAST_CW_n register will be
> >>> use.  
> >> >> "  
> >> In the case of QPIC v2, codewords 0, 1 and 2 will be accessed through
> >> READ_LOCATION_n, while codeword 3 will be accessed through
> >> READ_LOCATION_LAST_CW_n.
> >> "  
> >> >> When I read my own sentence, I feel that there is something wrong.  
> >> If there are only 4 codewords, I guess a QPIC v2 is able to use
> >> READ_LOCATION_3 or READ_LOCATION_LAST_CW_0 interchangeably. Isn't it?  
> >> >> I guess the point of having these "last_cw_n" registers is to support  
> >> up to 8 codewords, am I wrong? If this the case, the current patch
> >> completely fails doing that I don't get the point of such change.  
> > 
> > This register is only use to read last code word.
> > 
> > I have address all the comments from all the previous sub sequent
> > patches and pushed
> > all patches in only one series.
> > 
> > Please check.  
> 
>   The registers READ_LOCATION & READ_LOCATION_LAST are not associated with number of code words.
>   These two registers are used to access the location inside a code word.

Ok. Can you please explain what is a location then? Or point me to a
datasheet that explains it.

Bottom line question: why having READ_LOCATION_0, _1,... an
READ_LOCATION_LAST_0, _1, etc?

> So whether we are having 4 code words
>   or 8 code words it doesn't matter. If we wanted access the location within normal code word we have to
>   use READ_LOCATION register and if we wanted to access location in last code word then we have to use
>   READ_LOCATION_LAST.
> >   
> >> >>> Signed-off-by: Md Sadre Alam <mdalam@...eaurora.org>  

Thanks,
Miquèl