linux-kernel - Re: [PATCH] nvmem: include bit index in cell sysfs file name

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Date: Thu, 25 Jan 2024 14:06:45 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: "Arnd Bergmann" <arnd@...db.de>
Cc: "Arnd Bergmann" <arnd@...nel.org>, "Srinivas Kandagatla"
 <srinivas.kandagatla@...aro.org>, regressions@...ts.linux.dev,
 Rafał Miłecki <rafal@...ecki.pl>, "Chen-Yu Tsai"
 <wenst@...omium.org>, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 asahi@...ts.linux.dev, "Sven Peter" <sven@...npeter.dev>, "Michael Walle"
 <michael@...le.cc>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvmem: include bit index in cell sysfs file name

Hi Arnd,

arnd@...db.de wrote on Thu, 25 Jan 2024 13:15:26 +0100:

> On Wed, Jan 24, 2024, at 23:11, Miquel Raynal wrote:
> > Hi Arnd,
> >
> > arnd@...db.de wrote on Wed, 24 Jan 2024 20:49:53 +0100:
> >  
> >> On Wed, Jan 24, 2024, at 18:22, Miquel Raynal wrote:  
> >> > arnd@...nel.org wrote on Mon, 22 Jan 2024 16:34:10 +0100:
> >> >    
> >> >> From: Arnd Bergmann <arnd@...db.de>
> >> >> 
> >> >> 
> >> >> As far as I can tell, this is a problem for any device with multiple cells on
> >> >> different bits of the same address. Avoid the issue by changing the file name
> >> >> to include the first bit number.    
> >> >
> >> > There is only one bit number right? We are talking about byte offsets
> >> > so this value can only range from 0 to 7? If we understand each other
> >> > correctly then why not, I'm fine with the extra ",0" thing.    
> >> 
> >> On the Apple M1, the nvmem registers are 32 bit wide, so the
> >> bit numbers can go up to 31. I can imagine some system using
> >> 64-bit registers, but it's unlikely to be higher than that.  
> >
> > In this case we will soon or later have a problem again. Can we include
> > the full offset of the bit and not just the first digit?  
> 
> I thought that is what my patch does, maybe I don't
> undestand the problem you are referring to. This is what
> I see on my system with the patch applied:
> 
> $ cd /sys/devices/platform/soc@...000000/2922bc000.efuse
> $ find . -name efuse\*
> ./apple_efuses_nvmem0/cells/efuse@a24,11

Sorry for the misunderstanding, I thought the above situation would
be:

  ./apple_efuses_nvmem0/cells/efuse@a24,1

But the below output is actually fine.

Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>

> ./apple_efuses_nvmem0/cells/efuse@a24,9
> ./apple_efuses_nvmem0/cells/efuse@a1c,f
> ./apple_efuses_nvmem0/cells/efuse@a20,17
> ./apple_efuses_nvmem0/cells/efuse@a20,1e
> ./apple_efuses_nvmem0/cells/efuse@a18,0
> ./apple_efuses_nvmem0/cells/efuse@a14,b
> ./apple_efuses_nvmem0/cells/efuse@a1c,1f
> ./apple_efuses_nvmem0/cells/efuse@a1c,d
> ./apple_efuses_nvmem0/cells/efuse@a20,1c
> ./apple_efuses_nvmem0/cells/efuse@a18,15
> ./apple_efuses_nvmem0/cells/efuse@a14,0
> ./apple_efuses_nvmem0/cells/efuse@a1c,14
> ./apple_efuses_nvmem0/cells/efuse@a24,3
> ./apple_efuses_nvmem0/cells/efuse@a20,7
> ./apple_efuses_nvmem0/cells/efuse@a18,5
> ./apple_efuses_nvmem0/cells/efuse@a10,16
> ./apple_efuses_nvmem0/cells/efuse@a1c,12
> ./apple_efuses_nvmem0/cells/efuse@a20,5
> ./apple_efuses_nvmem0/cells/efuse@a18,3
> ./apple_efuses_nvmem0/cells/efuse@a18,a
> ./apple_efuses_nvmem0/cells/efuse@a10,1b
> ./apple_efuses_nvmem0/cells/efuse@a14,5
> ./apple_efuses_nvmem0/cells/efuse@a1c,19
> ./apple_efuses_nvmem0/cells/efuse@a24,f
> ./apple_efuses_nvmem0/cells/efuse@a18,1d
> ./apple_efuses_nvmem0/cells/efuse@a14,13
> ./apple_efuses_nvmem0/cells/efuse@a18,8
> ./apple_efuses_nvmem0/cells/efuse@a18,f
> ./apple_efuses_nvmem0/cells/efuse@a20,14
> ./apple_efuses_nvmem0/cells/efuse@a10,19
> ./apple_efuses_nvmem0/cells/efuse@a18,1b
> ./apple_efuses_nvmem0/cells/efuse@a14,11
> ./apple_efuses_nvmem0/cells/efuse@a1c,a
> ./apple_efuses_nvmem0/cells/efuse@a10,1e
> ./apple_efuses_nvmem0/cells/efuse@a20,19
> 
>       Arnd


Thanks,
Miquèl