[PATCH v3 6/6] mtd: rawnand: meson: rename node for chip select
Arseniy Krasnov
avkrasnov at sberdevices.ru
Thu May 11 07:22:24 PDT 2023
On 11.05.2023 15:11, Miquel Raynal wrote:
> Hi Arseniy,
>
> avkrasnov at sberdevices.ru wrote on Thu, 11 May 2023 13:16:59 +0300:
>
>> On 11.05.2023 12:17, Arseniy Krasnov wrote:
>>>
>>>
>>> On 11.05.2023 12:12, Miquel Raynal wrote:
>>>> Hi Arseniy,
>>>>
>>>> avkrasnov at sberdevices.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 at googlemail.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 at sberdevices.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 at 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 at 7800 {
>>>>> compatible = "amlogic,meson-axg-nfc";
>>>>> ...
>>>>> nand at 0 {
>>>>> reg = <0>;
>>>>> };
>>>>> }
>>>>>
>>>>> I checked, that 'nand_set_flash_node()' is called with 'nand at 0' and i suppose
>>>>> that it is correct (as You mentioned below). But, 'nvmem_add_cells_from_of()' is called
>>>>> with parent: 'nfc at 7800', then it iterates over its childs, e.g. 'nand at 0' and thus i get such
>>>>> situation. I guess, that 'nvmem_add_cells_from_of()' must be called with 'nand at 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 at 0 {
>> reg = <0>;//chip select
>>
> partitions {
> compatible = ...
>
>> otp at 0 {
>> #address-cells = <2>;
>> #size-cells = <0>;
>
> #address/size-cells is not needed here
>
>> compatible = "user-otp";
>> reg = <A B>;
>> };
>> otp at 1 {
>> #address-cells = <2>;
>> #size-cells = <0>;
>
> Ditto
>
>> compatible = "factory-otp";
>> reg = <C D>;
>> };
>
> };
>
>> };
>>
>> Now nvmem subsystem parses 'otp at 0' and 'otp at 1' and error is gone. 'compatible' values are
>> the same as in drivers/mtd/mtdcore.c:mtd_otp_nvmem_add(). 'reg' in 'nand at 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 at 7800 {
compatible = "amlogic,meson-axg-nfc";
...
nand at 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 at 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 at 7800'
also looking for "reg" value in each of its child. In this case it found "reg" in 'nand at 0'
and fails.
Now, if i add "compatible = "user-otp";" to 'nand at 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
>
>>
>> I think, this patch should be abandoned in the next version.
>>
>> Thanks, Arseniy
>>
>>>
>>>>
>>>> Thanks,
>>>> Miquèl
>
>
> Thanks,
> Miquèl
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