linux-kernel - Re: [PATCH v4 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

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Date:   Thu, 30 Apr 2020 16:30:15 +0800
From:   "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     qi-ming.wu@...el.com, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        cheol.yong.kim@...el.com, hauke.mehrtens@...el.com,
        anders.roxell@...aro.org, vigneshr@...com, arnd@...db.de,
        richard@....at, brendanhiggins@...gle.com,
        linux-mips@...r.kernel.org, robh+dt@...nel.org,
        miquel.raynal@...tlin.com, tglx@...utronix.de,
        masonccyang@...c.com.tw, andriy.shevchenko@...el.com
Subject: Re: [PATCH v4 2/2] mtd: rawnand: Add NAND controller support on Intel
 LGM SoC

H Boris,

On 30/4/2020 4:21 pm, Boris Brezillon wrote:
> On Thu, 30 Apr 2020 15:50:30 +0800
> "Ramuthevar, Vadivel MuruganX"
> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
> 
>> Hi Boris,
>>
>>     Thank you very much for keep reviewing the patches and more queries...
>>
>> On 29/4/2020 11:31 pm, Boris Brezillon wrote:
>>> On Wed, 29 Apr 2020 23:18:31 +0800
>>> "Ramuthevar, Vadivel MuruganX"
>>> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>>>    
>>>> Hi Boris,
>>>>
>>>> On 29/4/2020 10:48 pm, Boris Brezillon wrote:
>>>>> On Wed, 29 Apr 2020 22:33:37 +0800
>>>>> "Ramuthevar, Vadivel MuruganX"
>>>>> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>>>>>       
>>>>>> Hi Boris,
>>>>>>
>>>>>> On 29/4/2020 10:22 pm, Boris Brezillon wrote:
>>>>>>> On Wed, 29 Apr 2020 18:42:05 +0800
>>>>>>> "Ramuthevar, Vadivel MuruganX"
>>>>>>> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>>>>>>>          
>>>>>>>> +
>>>>>>>> +#define EBU_ADDR_SEL(n)		(0x20 + (n) * 4)
>>>>>>>> +#define EBU_ADDR_MASK		(5 << 4)
>>>>>>>
>>>>>>> It's still unclear what ADDR_MASK is for. Can you add a comment
>>>>>>> explaining what it does?
>>>>>>
>>>>>> Thank you Boris, keep review and giving inputs, will update.
>>>>>
>>>>> Can you please explain it here before sending a new version?
>>>>
>>>> Memory Region Address Mask:
>>>> Specifies the number of right-most bits in the base address that should
>>>> be included in the address comparison. bits positions(7:4).
>>>
>>> Okay, then the macro should be
>>>
>>> #define EBU_ADDR_MASK(x)	((x) << 4)
>>>
>>> And now I'd like you to explain why 5 is the right value for that field
>>> (I guess that has to do with the position of the CS/ALE/CLE pins).
>>
>> 5 : bit 26, 25, 24, 23, 22 to be included for comparison in the
> 
> That's 6 bits to me, not 5.

No , 5 bits only the above case.
> 
>> ADDR_SELx , it compares only 5 bits.
> 
> Definitely not what I would qualify as right-most bits. So, you say the
> comparison always starts at bit 22, and ends at 22+<num-addr-bits>?

Correct

> 
>>>>>> Yes , we are setting both CS0 and CS1 memory access region, if you have
>>>>>> any concern to optimize, please suggest me, Thanks!
>>>>>
>>>>> If you want to setup both CS, and the address written in EBU_ADDR_SEL(x)
>>>>> is really related to the nand_pa address, then retrieve resources for
>>>>> all CS ranges.
>>>> If it's not related, please explain what those
>>>>> EBU_MEM_BASE_CS_X values encode.
>>>>
>>>> Memory Region Base Address
>>>> FPI Bus addresses are compared to this base address in conjunction with
>>>> the mask control(EBU_ADDR_MASK). Driver need to program this field!
>>>
>>> That's not explaining what the base address should be. Is 'nand_pa' the
>>> value we should have there?
>>
>> The one prorgrammed in the addr_sel register is used by the HW
>> controller, it remaps to  0x174XX-> CS0 and 0x17CXX->CS1.
>> The hardware itself, decodes only for 1740xx/17c0xx, other random values
>> cannot be programmed
> 
> The question is, is it the same value we have in nand_pa or it is
> different?
> 
Different address which is 0xE1400000 NAND_BASE_PHY address.

Thanks!

Regards
Vadivel