linux-kernel - Re: [PATCH v4] mtd: spi-nor: add support for GD25Q256

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Date:   Wed, 16 Aug 2017 11:40:27 +0800
From:   Andy Yan <andy.yan@...k-chips.com>
To:     Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>
Cc:     linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        boris.brezillon@...e-electrons.com, marek.vasut@...il.com,
        computersforpeace@...il.com, richard@....at, dwmw2@...radead.org
Subject: Re: [PATCH v4] mtd: spi-nor: add support for GD25Q256

Hi Cyrille:


On 2017年08月16日 00:04, Cyrille Pitchen wrote:
> Hi Andy,
>
> Le 25/07/2017 à 12:12, Andy Yan a écrit :
>> Add support for GD25Q256, a 32MiB SPI Nor
>> flash from Gigadevice.
>>
>> Signed-off-by: Andy Yan <andy.yan@...k-chips.com>
>>
>> ---
>>
>> Changes in v4:
>> - add SPI_NOR_HAS_LOCK and SPI_NOR_HAS_TB
> Between v3 and v4, I see that you've also changed the procedure to the
> the Quad Enable bit on all Gigadevice memories with QSPI capabilities.
> This is not a detail and should have been reported here.

  Sorry, I will keep this in mind.
>
>> Changes in v3:
>> - rebase on top of spi-nor tree
>> - add SPI_NOR_4B_OPCODES flag
>>
>> Changes in v2:
>> - drop one line unnecessary modification
>>
>>   drivers/mtd/spi-nor/spi-nor.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index 196b52f..e4145cd 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -986,6 +986,11 @@ static const struct flash_info spi_nor_ids[] = {
>>   			SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
>>   			SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
>>   	},
>> +	{
>> +		"gd25q256", INFO(0xc84019, 0, 64 * 1024, 512,
>> +			SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
>> +			SPI_NOR_4B_OPCODES | SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB)
>> +	},
>>   
>>   	/* Intel/Numonyx -- xxxs33b */
>>   	{ "160s33b",  INFO(0x898911, 0, 64 * 1024,  32, 0) },
>> @@ -2365,6 +2370,7 @@ static int spi_nor_init_params(struct spi_nor *nor,
>>   				   SNOR_HWCAPS_PP_QUAD)) {
>>   		switch (JEDEC_MFR(info)) {
>>   		case SNOR_MFR_MACRONIX:
>> +		case SNOR_MFR_GIGADEVICE:
>>   			params->quad_enable = macronix_quad_enable;
> Here, you've have changed the Quad Enable requirement for *all*
> Gigadevice memories with Quad SPI capabilities.
>
> However, I'm reading the GD25Q128 datasheet and it claims that the QE
> bit is BIT(1) of the Status Register 2. Hence some
> spansion*_quad_enable() should be used, as before your patch.
>
> Then, still according to the datasheet, the GD25Q128 memory is compliant
> with the JESD216 specification (minor 0) but neither with rev A (minor
> 5) nor rev B (minor 6).
> So its Basic Flash Parameter Table is limited to 9 DWORDs instead of 16
> DWORDs, hence doesn't provide the Quad Enable requirements. It means
> that the SFDP tables would not help to select the right _quad_enable()
> function by overriding the choice made by the switch() statement above.
>
> tl;dr
> This chunk would introduce a regression with some already supported
> Gigadevice memories. So I reject this patch, sorry.

     After check some other Gigadevice memories, I found it's true as 
you mentioned.
Some memories use S9 as the QE bit, but some use S6.
     Do you have some ideas for this case? Add a check for the full 
jedec_id or encode
the QE bit in the flash_info?
     I am a new bee in the flash failed, very appreciate for your advice.
>
> Best regards,
>
> Cyrille
>
>>   			break;
>>   
>>
>
>
>