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

[Liang Yang]

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.

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.

> > 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