linux-kernel - Re: [PATCH v3 6/6] mtd: rawnand: meson: rename node for chip select

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Message-ID: <20230511111204.0b0b3d70@xps-13>
Date:   Thu, 11 May 2023 11:12:04 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>, <oxffffaa@...il.com>,
        <kernel@...rdevices.ru>, <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 6/6] mtd: rawnand: meson: rename node for chip select

Hi Arseniy,

avkrasnov@...rdevices.ru wrote on Thu, 11 May 2023 11:59:07 +0300:

> On 10.05.2023 23:53, Miquel Raynal wrote:
> 
> Hello Martin, Miquel
> 
> > Hi Martin & Arseniy,
> > 
> > martin.blumenstingl@...glemail.com wrote on Wed, 10 May 2023 22:40:37
> > +0200:
> >   
> >> Hello Arseniy,
> >>
> >> On Wed, May 10, 2023 at 1:13 PM Arseniy Krasnov
> >> <AVKrasnov@...rdevices.ru> wrote:  
> >>>
> >>> This renames node with values for chip select from "reg" to "cs". It is
> >>> needed because when OTP access is enabled on the attached storage, MTD
> >>> subsystem registers this storage in the NVMEM subsystem. NVMEM in turn
> >>> tries to use "reg" node in its own manner, supposes that it has another
> >>> layout. All of this leads to device initialization failure.    
> >> In general: if we change the device-tree interface (in this case:
> >> replacing a "reg" with a "cs" property) the dt-bindings have to be
> >> updated as well.  
> > 
> > True, and I would add, bindings should not be broken.  
> 
> I see, that's true. That is bad way to change bindings.
> 
> >   
> >> Documentation/devicetree/bindings/mtd/nand-controller.yaml and
> >> Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml show
> >> that the chip select of a NAND chip is specified with a "reg"
> >> property.  
> > 
> > All NAND controller binding expect the chip-select to be in the
> > 'reg' property, very much like a spi device would use reg to store the
> > cs as well: the reg property tells you how you address the device.
> > 
> > I also fully agree with Martin's comments below. Changing reg is likely
> > a wrong approach :)
> >   
> >> Also the code has to be backwards compatible with old .dtbs.
> >>  
> >>> Example:
> >>>
> >>> [...] nvmem mtd0-user-otp: nvmem: invalid reg on /soc/bus@...00000/...
> >>> [...] mtd mtd0: Failed to register OTP NVMEM device
> >>> [...] meson-nand ffe07800.nfc: failed to register MTD device: -22
> >>> [...] meson-nand ffe07800.nfc: failed to init NAND chips
> >>> [...] meson-nand: probe of ffe07800.nfc failed with error -22    
> >> This is odd - can you please share your definition of the &nfc node?  
> 
> Sure, here it is:
> 
> mtd_nand: nfc@...0 {                            
> 	compatible = "amlogic,meson-axg-nfc";
> 	...
> 	nand@0 {                                
>         	reg = <0>;
>         };
> }
> 
> I checked, that 'nand_set_flash_node()' is called with 'nand@0' and i suppose
> that it is correct (as You mentioned below). But, 'nvmem_add_cells_from_of()' is called
> with parent: 'nfc@...0', then it iterates over its childs, e.g. 'nand@0' and thus i get such
> situation. I guess, that 'nvmem_add_cells_from_of()' must be called with 'nand@0' ?

We recently had issues with nvmem parsing, but I believe a mainline
kernel should now be perfectly working on this regard. What version of
the Linux kernel are you using?

Thanks,
Miquèl