Message-ID: <6d5ea6d8-d8c6-0875-f0b3-2fcaac64899d@quicinc.com>
Date:   Mon, 6 Mar 2023 20:03:41 +0530
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Subject: Re: [PATCH 2/5] mtd: rawnand: qcom: Add initial support for qspi nand
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To:     Boris Brezillon <boris.brezillon@collabora.com>
CC:     <linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-mtd@lists.infradead.org>, <linux-arm-msm@vger.kernel.org>,
        <robh+dt@kernel.org>, <vigneshr@ti.com>, <richard@nod.at>,
        <miquel.raynal@bootlin.com>, <agross@kernel.org>,
        <bjorn.andersson@linaro.org>, <quic_srichara@quicinc.com>,
        <qpic_varada@quicinc.com>, <quic_sjaganat@quicinc.com>
References: <1602307902-16761-1-git-send-email-mdalam@codeaurora.org>
 <1602307902-16761-3-git-send-email-mdalam@codeaurora.org>
 <20201029100751.713e27df@collabora.com>
 <b70ddb40-a1f1-f967-6b7b-057a39b0bcc2@quicinc.com>
From:   Md Sadre Alam <quic_mdalam@quicinc.com>
In-Reply-To: <b70ddb40-a1f1-f967-6b7b-057a39b0bcc2@quicinc.com>
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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@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                                |             |    
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.
>
>
>>