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

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Arseniy,

avkrasnov@sberdevices.ru wrote on Tue, 6 Jun 2023 10:40:21 +0300:

> 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.

It needs to be very well contained in dedicated helpers and documented.
You choose what is easier for you (Liang's method or
nand_soft_waitrdy()), but I don't want to see spurious READ0 or
READ_STATUS calls inside read/write_page helpers like before.

> 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  


Thanks,
Miquèl

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