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

[Md Sadre Alam]

On 10/29/2020 2:37 PM, Boris Brezillon wrote:
> Hello,
>
> On Sat, 10 Oct 2020 11:01:39 +0530
> Md Sadre Alam <mdalam at codeaurora.org> 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 IO_MACRO     
        |        |

                                     |                           |     
                         QPIC           |               |             
(control the SPI BUS         |        | 
-------------------------------------------------->  Serial NAND IOs

                                     |                           |     
        QPIC_SPI_CFG = 1       --------------->     |          |         
        internally)                            |         |  
-------------------------------------------------->

                                     |                           |     
            |               |                             |         |

                                     | |                 |               
|_____________________________|      |

                                     |                           |     
            | | |

                                     |                           |     
         |               |  _____________________________|     |

                                     |                           |     
          |               |                                 |        | 
                                       | |                  
|               | Ebi2_ext_if                       |         |

                                     | | | | |         |

                                    |                            |    
          QPIC_SPI_CFG = 0  ----------------------> |           |       
       | |-------------------------------------------------> Parallel 
NAND IOs

                                    |                            |     
             |               |                                  | 
|--------------------------------------------------->

<------------------------------------------ 
|_____________|_____________________________________|_______|______________________________|____|

                            AHB Slave IF


   Regards,

Alam.


>