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

[Arseniy Krasnov]

On 12.05.2023 17:49, Miquel Raynal wrote:
> Hi Arseniy,
> 
> I'm adding Rafał & Michael: any idea what could be wrong? The behavior
> below does not look expected at all, but I thought we (= Rafał, mainly)
> already sorted this out?
> 

Hi Miquel, thanks for help!

just to clarify an expected behaviour: if i have the following layout in the device tree

mtd_nand: nfc@7800 {                            
 	compatible = "amlogic,meson-axg-nfc";
 	...
 	nand@0 {                                
         	reg = <0>;
         };
}

node used by 'nvmem_add_cells_from_of()' must be NULL? or 'nand@0'?

I guess, that in above dts I have node 'nfc@7800' in use, because 'mtd_otp_nvmem_register()' uses
the following device before passing 'config' to 'nvmem_register()':

        /* OTP nvmem will be registered on the physical device */       
        config.dev = mtd->dev.parent;

'mtd->dev.parent' is 'nfc@7800'.

May be 'mtd_otp_nvmem_register()' must initialize 'no_of_node' field of 'config' like in 'mtd_nvmem_add()' ?
This field is documented as:

* @no_of_node:	Device should not use the parent's of_node even if it's !NULL.

In this case node passed to 'nvmem_add_cells_from_of()' will be NULL.

Thanks, 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?    
>>>>>
>>>>> My current version is:
>>>>>
>>>>> VERSION = 6                                                             
>>>>> PATCHLEVEL = 2                                                          
>>>>> SUBLEVEL = 0                                                            
>>>>> EXTRAVERSION = -rc8 
>>>>>
>>>>> Fix was in drivers/nvmem/* ?
>>>>>
>>>>> Thanks, Arseniy    
>>>>
>>>> Upd: I resolved problem in the following way:
>>>>
>>>> nand@0 {                                
>>>> 	reg = <0>;//chip select
>>>>  
>>> 	partitions {
>>> 		compatible = ...
>>>   
>>>> 	otp@0 {                         
>>>> 		#address-cells = <2>;   
>>>> 		#size-cells = <0>;        
>>>
>>> #address/size-cells is not needed here
>>>   
>>>> 		compatible = "user-otp";
>>>> 		reg = <A B>;            
>>>> 	};                              
>>>> 	otp@1 {                         
>>>> 		#address-cells = <2>;   
>>>> 		#size-cells = <0>;        
>>>
>>> Ditto
>>>   
>>>> 		compatible = "factory-otp";
>>>> 		reg = <C D>;            
>>>> 	};                                
>>>
>>> 	};
>>>   
>>>> };
>>>>
>>>> Now nvmem subsystem parses 'otp@0' and 'otp@1' and error is gone. 'compatible' values are
>>>> the same as in drivers/mtd/mtdcore.c:mtd_otp_nvmem_add(). 'reg' in 'nand@0' is used as
>>>> chip select as supposed.  
>>>
>>> I don't fully get it. The parsing on the nvmem side should not fail if
>>> there is no subpartition/otp-region defined. Can you confirm an empty
>>> NAND device node works? Because your last e-mail suggested the opposite.  
>>
>> Ok, so i'll describe what happens in my case. Let's NAND node be like this (IIUC this is
>> considered as empty NAND device):
>>
>> mtd_nand: nfc@7800 {                            
>> 	compatible = "amlogic,meson-axg-nfc";
>> 	...
>> 	nand@0 {                                
>> 	       	reg = <0>;
>> 	};
>> }
>>
>> I see, that
>>
>> 1) 'mtd_otp_nvmem_add()' calls 'mtd_otp_nvmem_register()' twice for two types of
>>    OTP memory "user-otp" and "factory-otp". Let's take a look only on "user-otp".
>> 2) 'mtd_otp_nvmem_register()' tries to lookup for node in 'nand@0' which is compatible with
>>    "user-otp" and then passes found (or not found, e.g. NULL) node to  'nvmem_register()'.
>> 3) 'nvmem_register()' uses this node iterating over its childs and searching value "reg" in
>>    each child. If "user-otp" node is not found in 2), 'nvmem_register()' uses node 'nfc@7800'
>>    also looking for "reg" value in each of its child. In this case it found "reg" in 'nand@0'
>>    and fails.
>>
>> Now, if i add "compatible = "user-otp";" to 'nand@0', in step 2) search will be successful,
>> and "reg" value will be used from this new node (or we remove "reg" from it - nothing happens
>> as You wrote). So, problem is that nvmem tries to parse node with invalid "reg" value.
>>
>> Also I see, that 'nvmem_register()' is called earlier in 'mtd_nvmem_add()', but with no effect.
>> I think, that it is not related with enabled OTP feature.
>>
>> Thanks, Arseniy