linux-kernel - Re: [PATCH 2/9] mtd: spi-nor: add an alternative method to support memory >16MiB

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Message-ID: <b95b1271-0ba1-91a7-ffc6-b2d47c42222d@ti.com>
Date:   Thu, 6 Oct 2016 15:33:39 +0530
From:   Vignesh R <vigneshr@...com>
To:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>
CC:     "marex@...x.de" <marex@...x.de>,
        "boris.brezillon@...e-electrons.com" 
        <boris.brezillon@...e-electrons.com>,
        "nicolas.ferre@...el.com" <nicolas.ferre@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/9] mtd: spi-nor: add an alternative method to support
 memory >16MiB



On Wednesday 05 October 2016 06:23 PM, Cyrille Pitchen wrote:
> Hi Vignesh,
> 
> Le 05/10/2016 à 14:12, Vignesh R a écrit :
>> Hi,
>>
>>
>> On Tuesday 04 October 2016 10:07 PM, Cyrille Pitchen wrote:
>> [...]
>>>  static struct seq_rw_config stfsm_s25fl_write4_configs[] = {
>>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>>> index 5c87b2d99507..423448c1c7a8 100644
>>> --- a/drivers/mtd/spi-nor/spi-nor.c
>>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>>> @@ -75,6 +75,10 @@ struct flash_info {
>>>  					 * bit. Must be used with
>>>  					 * SPI_NOR_HAS_LOCK.
>>>  					 */
>>> +#define SPI_NOR_4B_OPCODES	BIT(10)	/*
>>> +					 * Use dedicated 4byte address op codes
>>> +					 * to support memory size above 128Mib.
>>> +					 */
>>
>>
>> I don't see this flag being added to any flash_info data for any m25p80
>> compatible flashes? Is that part of a separate series?
>>
> 
> Indeed, this flag is not used yet by any entry in the spi_nor_ids[] array.
> At first, I tested this patch with a Macronix mx25l25673g memory.
> This memory shares the very same JEDEC ID as the older mx25l25635e, so
> I added the SPI_NOR_4B_OPCODES flag in the mx25l25635e entry during my test.
> However I didn't commit this change since the actual mx25l25635e memory
> doesn't support The 4-byte address instruction test.
> 
> Also the mx25l25673g provides the optional 4-byte Address Instruction Table,
> as described in the JESD216 rev B specification, so patches 6 and 7 allow
> to use the 4-byte address op codes without setting the SPI_NOR_4B_OPCODES flag.
> 
> Hence the SPI_NOR_4B_OPCODES, will be useful for memories which don't
> provide the JESD216B 4-byte Address Instruction Table but still support
> the associated op code. It will have to be tested for each individual entry
> in the spi_nor_ids[] array, which can be done later.
> 
> Anyway, the 4-byte address op codes introduced by this patch are also used
> by patch 7 (parse SFDP 4-byte Address Instruction Table).

OK, thanks for the explanation!


-- 
Regards
Vignesh