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Reply-To: vadivel.muruganx.ramuthevar@linux.intel.com
Subject: Re: [PATCH v4 2/2] mtd: rawnand: Add NAND controller support on Intel
 LGM SoC
To:     Boris Brezillon <boris.brezillon@collabora.com>
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From:   "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@linux.intel.com>
Message-ID: <eed59a7a-b91d-84cd-add0-31e108d87e6f@linux.intel.com>
Date:   Mon, 4 May 2020 09:54:35 +0800
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Hi Boris,

   Thank you very much for the review comments and giving inputs...

On 30/4/2020 8:36 pm, Boris Brezillon wrote:
> On Thu, 30 Apr 2020 17:07:03 +0800
> "Ramuthevar, Vadivel MuruganX"
> <vadivel.muruganx.ramuthevar@linux.intel.com> wrote:
> 
>>>>> 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.
>>>
>>> Then why didn't you tell me they didn't match when I suggested to pass
>>
>> sorry, because you keep asking nand_pa after that only I realized that.
>>
>>> nand_pa? So now the question is, what does this address represent?
>>
>>                  EBU-MODULE
>>    _________     _______________________
>> |         |   |            |NAND CTRL  |
>> | FPI BUS |==>| CS0(0x174) | 0xE100    ( 0xE14/0xE1C) NAND_PHY_BASE
>> |_________|   |_CS1(0x17C)_|__________ |
>>
>> EBU_CONRTROLLER_BASE : 0xE0F0_0000
>> HSNAND_BASE: 0xE100_0000
>> NAND_CS0: 0xE140_0000
>> NAND_CS1: 0xE1C0_0000
>>
>> MEM_REGION_BASE_CS0: 0x17400 (internal to ebu controller )
>> MEM_REGION_BASE_CS1: 0x17C00
>>
> 
> Hm, I wonder if we shouldn't use a 'ranges' property to describe this
> address translation. Something like
> 
> 	ebu@xxx {
> 		ranges = <0x17400000 0xe1400000 0x1000>,
> 			 <0x17c00000 0xe1c00000 0x1000>;
> 		reg = <0x17400000>, <0x17c00000>;
> 		reg-names = "cs-0", "cs-1";
> 	}
> 
> The translated address (0xE1X00000) will be available in res->start,
> and the non-translated one (0x17X00000) can be retrieved with
> of_get_address(). All you'd have to do then would be calculate the
> mask:
> 
> 	mask = (translated_address & original_address) >> 22;
> 	num_comp_bits = fls(mask);
> 	WARN_ON(mask != GENMASK(num_comp_bits - 1, 0));
> 
> Which allows you to properly set the ADDR_SEL() register without
> relying on some hardcoded values:
> 
> 	writel(original_address | EBU_ADDR_SEL_REGEN |
> 	       EBU_ADDR_COMP_BITS(num_comp_bits),
> 	       ebu_host->ebu + EBU_ADDR_SEL(csid));
> 
> That's quite important if we want to merge the xway NAND driver with
> this one.

Thanks! , for the optimized and made it generic way, will update in the 
next patch-set.

Regards
Vadivel
>