Re: [PATCH v5 1/3] mtd: spi-nor: add support for is25wp256

From: Vignesh Raghavendra <vigneshr@ti.com>
To: Sagar Kadam <sagar.kadam@sifive.com>
Cc: aou@eecs.berkeley.edu, tudor.ambarus@microchip.com,
	Wesley Terpstra <wesley@sifive.com>,
	richard@nod.at, Palmer Dabbelt <palmer@sifive.com>,
	linux-kernel@vger.kernel.org, marek.vasut@gmail.com,
	linux-mtd@lists.infradead.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	miquel.raynal@bootlin.com, linux-riscv@lists.infradead.org,
	computersforpeace@gmail.com, dwmw2@infradead.org
Subject: Re: [PATCH v5 1/3] mtd: spi-nor: add support for is25wp256
Date: Fri, 21 Jun 2019 11:34:21 +0530	[thread overview]
Message-ID: <93b9c5fd-8f59-96d7-5e40-2b9d540965dd@ti.com> (raw)
In-Reply-To: <CAARK3H=O=h1VDgOMxs_0ThcisrH=2tzpW5pQqt0O9oYs=MFFVw@mail.gmail.com>

Hi,

On 17/06/19 8:48 PM, Sagar Kadam wrote:
> Hello Vignesh,
> 
> Thanks for your review comments.
> 
> On Sun, Jun 16, 2019 at 6:14 PM Vignesh Raghavendra <vigneshr@ti.com> wrote:
>>
>> Hi,
>>
>> On 12-Jun-19 4:17 PM, Sagar Shrikant Kadam wrote:
>> [...]
>>
>>> @@ -4129,7 +4137,7 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
>>>       if (ret)
>>>               return ret;
>>>
>>> -     if (nor->addr_width) {
>>> +     if (nor->addr_width && JEDEC_MFR(info) != SNOR_MFR_ISSI) {
>>>               /* already configured from SFDP */
>>
>> Hmm, why would you want to ignore addr_width that's read from SFDP table?
> 
> The SFDP table for ISSI device considered here, has addr_width set to
> 3 byte, and the flash considered
> here is 32MB. With 3 byte address width we won't be able to access
> flash memories higher address range.

Is it specific to a particular ISSI part as indicated here[1]? If so,
please submit solution agreed there i.e. use spi_nor_fixups callback

[1]https://patchwork.ozlabs.org/patch/1056049/

> Hence I have ignored the addr width from SFDP.  I have verified that
> with 3 byte address width, the
> flascp util fails while verifying the written data.  Please let me
> know your views on this?
> 
If this affects multiple ISSI parts then:
Instead of checking for mfr code, look for SNOR_F_4B_OPCODES flag in
flash_info struct of the device and let it take precedence over SFDP in
case size is over 16MB

Regards
Vignesh

> BR,
> Sagar Kadam
> 
>> Regards
>> Vignesh
>>
>>
>>>       } else if (info->addr_width) {
>>>               nor->addr_width = info->addr_width;
>>> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
>>> index b3d360b..ff13297 100644
>>> --- a/include/linux/mtd/spi-nor.h
>>> +++ b/include/linux/mtd/spi-nor.h
>>> @@ -19,6 +19,7 @@
>>>  #define SNOR_MFR_ATMEL               CFI_MFR_ATMEL
>>>  #define SNOR_MFR_GIGADEVICE  0xc8
>>>  #define SNOR_MFR_INTEL               CFI_MFR_INTEL
>>> +#define SNOR_MFR_ISSI                0x9d            /* ISSI */
>>>  #define SNOR_MFR_ST          CFI_MFR_ST      /* ST Micro */
>>>  #define SNOR_MFR_MICRON              CFI_MFR_MICRON  /* Micron */
>>>  #define SNOR_MFR_MACRONIX    CFI_MFR_MACRONIX
>>>

-- 
Regards
Vignesh

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