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

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Message-ID: <dd25efa3-e46a-e857-d355-53330a8a4181@sberdevices.ru>
Date:   Thu, 11 May 2023 12:17:31 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
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



On 11.05.2023 12:12, Miquel Raynal wrote:
> 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?

My current version is:

VERSION = 6                                                             
PATCHLEVEL = 2                                                          
SUBLEVEL = 0                                                            
EXTRAVERSION = -rc8 

Fix was in drivers/nvmem/* ?

Thanks, Arseniy

> 
> Thanks,
> Miquèl