Re: [PATCH 2/5] mtd: rawnand: qcom: Add initial support for qspi nand

[Md Sadre Alam]

On 3/6/2023 7:45 PM, Md Sadre Alam wrote:
> On 10/29/2020 2:37 PM, Boris Brezillon wrote:
> > Hello,
> >
> > On Sat, 10 Oct 2020 11:01:39 +0530
> > Md Sadre Alam <mdalam@xxxxxxxxxxxxxx> wrote:
> >
> > > This change will add initial support for qspi (serial nand).
> > >
> > > QPIC Version v.2.0 onwards supports serial nand as well so this
> > > change will initialize all required register to enable qspi (serial
> > > nand).
> > >
> > > This change is supporting very basic functionality of qspi nand flash.
> > >
> > > 1. Reset device (Reset QSPI NAND device).
> > >
> > > 2. Device detection (Read id QSPI NAND device).
> > Unfortunately, that's not going to work in the long term. You're
> > basically hacking the raw NAND framework to make SPI NANDs fit. I do
> > understand the rationale behind this decision (re-using the code for
> > ECC and probably other things), but that's not going to work. So I'd
> > recommend doing the following instead:
> >
> > 1/ implement a SPI-mem controller driver
> > 2/ implement an ECC engine driver so the ECC logic can be shared
> >     between the SPI controller and raw NAND controller drivers
> > 3/ convert the raw NAND driver to the exec_op() interface (none of
> >     this hack would have been possible if the driver was using the new
> >     API)
> >
> > Regards,
> >
> > Boris
>    Sorry for late reply, again started working on this feature 
> support.  The QPIC v2 on wards there is serial nand support got added 
> , its not a standard SPI controller
>
>    its QPIC controller having support for serial nand. All SPI related 
> configuration done by QPIC hardware and its not exposed as SPI bus to 
> the external world. Only based on
>
>    QPIC_SPI_CFG = 1, serial functionality will get selected. So that 
> no need to implement as SPI-mem controller driver, since its not a SPI 
> controller.
>
>   Please check the below diagram for top view of QPIC controller.
___________________________________________________________________________

| QPIC wrapper                        |

            AHB master IF                                     | 
|_______________________                __________________________     
            |

<-------------------------------------------------     |                 
  |          QPIC                                |             |    
QPIC_IO_MACRO | |--------------------------------------------->Serial 
NAND IOs

|                        |     QPIC_SPI_CFG = 1     ----> |             
| (Control SPI Bus internally) | 
|--------------------------------------------->

| |                                                   | | 
|                 |

| |                                                   | | 
|                  |

| |                                                   | 
|__________________________|                 |

| |                                                    |          _ 
___________________________                 |

| |                                                    | |               
Ebi2_ext_if                        | |

|                        |   QPIC_SPI_CFG=0     -------> | | | 
|------------------------------------------------->

| |                                                     | | | 
|-------------------------------------------------->Parallel NAND IOs

<----------------------------------------------------   |               
   |________________________ |           | __________________________| 
             |

          AHB Slav IF | |

|_____________________________________________________________________________|

>   Regards,
>
> Alam.
>
>
> >