linux-kernel - Re: [PATCH v5 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

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Date:   Thu, 7 May 2020 14:38:52 +0800
From:   "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, miquel.raynal@...tlin.com,
        richard@....at, vigneshr@...com, arnd@...db.de,
        brendanhiggins@...gle.com, tglx@...utronix.de,
        anders.roxell@...aro.org, masonccyang@...c.com.tw,
        robh+dt@...nel.org, linux-mips@...r.kernel.org,
        hauke.mehrtens@...el.com, andriy.shevchenko@...el.com,
        qi-ming.wu@...el.com, cheol.yong.kim@...el.com
Subject: Re: [PATCH v5 2/2] mtd: rawnand: Add NAND controller support on Intel
 LGM SoC

Hi Boris,

   Thank you very much for the review comments and your time...

On 7/5/2020 2:27 pm, Boris Brezillon wrote:
> On Thu, 7 May 2020 14:13:42 +0800
> "Ramuthevar, Vadivel MuruganX"
> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
> 
>> Hi Boris,
>>
>>      Thank you very much for the review comments and your time...
>>
>> On 7/5/2020 1:28 pm, Boris Brezillon wrote:
>>> On Thu,  7 May 2020 08:15:37 +0800
>>> "Ramuthevar,Vadivel MuruganX"
>>> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>>>    
>>>> +	reg = readl(ebu_host->ebu + EBU_ADDR_SEL(ebu_host->cs_num));
>>>> +	writel(reg | EBU_ADDR_MASK(5) | EBU_ADDR_SEL_REGEN,
>>>> +	       ebu_host->ebu + EBU_ADDR_SEL(ebu_host->cs_num));
>>>
>>> Seriously, did you really think I would not notice what you're doing
>>> here?
>> Yes , I know that you have very good understanding about this.
>>    You're reading the previous value which either contains a default
>>> mapping or has the mapping set by the bootloader, and write it back to
>>> the register along with a new mask and the REGEN bit set (which
>>> BTW is wrong since you don't mask out other fields before updating
>>> them).
>> There is no other field get overwritten
>>    This confirms that this Core -> FPI address translation exists
>>> and has to be set properly, so please stop lying about that.
>>
>> Sorry, there is no SW translation, as I have mentioned that it's
>> optional only, for safer side , reading and writing the default values.
> 
> Then write EBU_ADDR_SEL_REGEN and we'll if see that works. I suspect it
> won't.

You mean, without reading just writing EBU_ADDR_SEL_REGEN bit alone in 
EBU_ADDR_SELx , as you said it won't work because it overwrites 0x174 
with 0x0 values so BASE is lost.
either we can leave it or read & write with ORed | EBU_ADDR_SEL_REGEN

Please correct me if anything is wrong, Thanks!
> 
>> The memory region to enabled that's my concern so written the same
>> register values.
> 
> I don't buy that, sorry.
> 
>>
>> This will not be impact other fields, so please see below for reference
>>
>> The EBU Address Select Registers EBU_ADDR_SEL_0 to EBU_ADDSEL3 establish
>> and control memory regions for external accesses.
>>
>> Reset Value: 17400001H
> 
> See, as suspected the reset value is exactly what you expect.

Yes , that's the reason said being optional.

Regards
Vadivel
>