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

[Miquel Raynal]

Hi Arseniy,

avkrasnov@xxxxxxxxxxxxxx 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@xxxxxxxxxxxxxx wrote on Wed, 10 May 2023 22:40:37
> > +0200:
> >   
> >> Hello Arseniy,
> >>
> >> On Wed, May 10, 2023 at 1:13 PM Arseniy Krasnov
> >> <AVKrasnov@xxxxxxxxxxxxxx> 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@ffe00000/...
> >>> [...] 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@7800 {                            
> 	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@7800', 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