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

[Liang Yang]

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.

> 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