Re: [RFC PATCH v5 2/6] mtd: rawnand: meson: wait for command in polling mode

[Arseniy Krasnov <avkrasnov@sberdevices.ru>]

On 06.06.2023 10:03, Miquel Raynal wrote:
> Hi Arseniy,
> 
> avkrasnov@sberdevices.ru wrote on Mon, 5 Jun 2023 19:58:02 +0300:
> 
>> On 05.06.2023 16:30, Liang Yang wrote:
>>>
>>>
>>> On 2023/6/5 21:19, Liang Yang wrote:  
>>>> Hi Miquel and Arseniy,
>>>>
>>>>
>>>> On 2023/6/5 17:05, Miquel Raynal wrote:  
>>>>> [ EXTERNAL EMAIL ]
>>>>>
>>>>> Hi Arseniy,
>>>>>  
>>>>>>>> @@ -1412,6 +1419,8 @@ static int meson_nfc_probe(struct platform_device *pdev)
>>>>>>>>             return ret;
>>>>>>>>     }
>>>>>>>>
>>>>>>>> +  nfc->use_polling = of_property_read_bool(dev->of_node, "polling");  
>>>>>>>
>>>>>>> This is a problem. You cannot add a polling property like that.
>>>>>>>
>>>>>>> There is already a nand-rb property which is supposed to carry how are
>>>>>>> wired the RB lines. I don't see any in-tree users of the compatibles, I
>>>>>>> don't know how acceptable it is to consider using soft fallback when
>>>>>>> this property is missing, otherwise take the values of the rb lines
>>>>>>> provided in the DT and user hardware control, but I would definitely
>>>>>>> prefer that.  
>>>>>>
>>>>>> I see. So i need to implement processing of this property here? And if it
>>>>>> is missed -> use software waiting. I think interesting thing will be that:
>>>>>>
>>>>>> 1) Even with support of this property here, I really don't know how to pass
>>>>>>     RB values to this controller - I just have define for RB command and that's
>>>>>>     it. I found that this property is an array of u32 - IIUC each element is
>>>>>>     RB pin per chip. May be i need to dive into the old vendor's driver to find
>>>>>>     how to use RB values (although this driver uses software waiting so I'm not
>>>>>>     sure that I'll find something in it).  
>>>>>
>>>>> Liang, can you please give use the relevant information here? How do we
>>>>> target RB0 and RB1? It seems like you use the CS as only information
>>>>> like if the RB lines where hardwired internally to a CS. Can we invert
>>>>> the lines with a specific configuration?  
>>>>
>>>> Controllor has only one external RB pinmux (NAND_RB0). all the RB pins
>>>> of different CEs need to be bound into one wire and connect with
>>>> NAND_RB0 if want to use controller polling rb. the current operating
>>>> CE of NAND is decided to "chip_select", of course controller internally has different nfc commands to regconize which Ce's RB signal is polling.
>>>>
>>>> <&nand_pins> in dts/yaml should include the NAND_RB0 if hardware connects, or use software polling here.
>>>>
>>>> @Arseniy, sorry, i don't travel all the informations yet. but why don't you use the new RB_INT command with irq that i provided in another thread. the new RB_INT command doesn't depend on the physical RB wires, it also send the READ status command(0x70) and wait for the irq wake up completion.  
>>
>> Technically no problem! I can use new RB_INT instead of 'nand_soft_waitrdy()' as software fallback, and currently
>> implemented RB_INT as interrupt driven way. What do You think Miquel ?
>>
>>>
>>> Use "nand-rb" in dts to decide old RB_INT(physical RB wires is needed) or new RB_INT(no physical RB wires). the new RB_INT command decides the RB0 or RB1 by the previous command with ce args.
>>>   
>>
>> So I can implement "nand-rb" in dts as boolean value - "false" or missing means use "no physical RB wires", "true" - means use "physical RB wires" ?
> 
> As long as it works and does not contain any extremely strange READ0 or
> READ_STATUS in the middle of nothing, I'm fine, take the simplest
> approach which will work for all.

"extremetely strange READ0" is method which uses STATUS, interrupt, READ0? This method was
described by Liang.

And You mean to use the following logic:
if ("nand-rb" == true)
    use RB_INT which requires wire
else
    use 'nand_soft_waitrdy()'

?

Thanks, Arseniy

> 
>>
>> Thanks, Arseniy
>>
>>>>  
>>>>> Arseniy, if the answer to my above question is no, then you should
>>>>> expect the nand-rb and reg arrays to be identical. If they are not,
>>>>> then you can return -EINVAL.
>>>>>
>>>>> If the nand-rb property is missing, then fallback to software wait.
>>>>>  
>>>>>> 2) I can't test RB mode - I don't have such device :(
>>>>>>
>>>>>> Also for example in arasan-nand-controller.c parsed 'nand-rb' values are used
>>>>>> in controller specific register for waiting (I guess Meson controller has something
>>>>>> like that, but I don't have doc). While in marvell_nand.c it looks like that they parse
>>>>>> 'nand-rb' property, but never use it.  
>>>>>
>>>>> Yes, the logic around the second RB line (taking care of CS1/CS3) is
>>>>> slightly broken or at least badly documented, and thus should not be
>>>>> used.
>>>>>  
>>>>>>> In any case you'll need a dt-binding update which must be acked by
>>>>>>> dt-binding maintainers.  
>>>>>>
>>>>>> You mean to add this property desc to Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml ?  
>>>>>
>>>>> Yes. In a dedicated patch. Something along the lines:
>>>>>
>>>>>          nand-rb: true
>>>>>
>>>>> inside the nand chip object should be fine. And flag the change as a
>>>>> fix because we should have used and parsed this property since the
>>>>> beginning.
>>>>>
>>>>> Thanks,
>>>>> Miquèl  
> 
> 
> Thanks,
> Miquèl

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