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

[Miquel Raynal]

Hi Arseniy,

avkrasnov@xxxxxxxxxxxxxx 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.

> 
> 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