linux-kernel - Re: [RESEND PATCH v2] mtd: spi-nor: Fix address width on flash chips

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Message-ID: <096b2b97-6b6b-a46e-1239-e5d257e80c0b@ti.com>
Date:   Wed, 7 Oct 2020 12:59:56 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Pratyush Yadav <p.yadav@...com>, Bert Vermeulen <bert@...t.com>
CC:     <tudor.ambarus@...rochip.com>, <miquel.raynal@...tlin.com>,
        <richard@....at>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v2] mtd: spi-nor: Fix address width on flash chips
 > 16MB



On 10/6/20 8:48 PM, Pratyush Yadav wrote:
> On 06/10/20 03:23PM, Bert Vermeulen wrote:
>> If a flash chip has more than 16MB capacity but its BFPT reports
>> BFPT_DWORD1_ADDRESS_BYTES_3_OR_4, the spi-nor framework defaults to 3.
>>
>> The check in spi_nor_set_addr_width() doesn't catch it because addr_width
>> did get set. This fixes that check.
>>
>> Fixes: f9acd7fa80be ("mtd: spi-nor: sfdp: default to addr_width of 3 for configurable widths")
>> Signed-off-by: Bert Vermeulen <bert@...t.com>
>> Reviewed-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
>> ---
>>  drivers/mtd/spi-nor/core.c | 8 +++++---
>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> index 0369d98b2d12..a2c35ad9645c 100644
>> --- a/drivers/mtd/spi-nor/core.c
>> +++ b/drivers/mtd/spi-nor/core.c
>> @@ -3009,13 +3009,15 @@ static int spi_nor_set_addr_width(struct spi_nor *nor)
>>  		/* already configured from SFDP */
>>  	} else if (nor->info->addr_width) {
>>  		nor->addr_width = nor->info->addr_width;
>> -	} else if (nor->mtd.size > 0x1000000) {
>> -		/* enable 4-byte addressing if the device exceeds 16MiB */
>> -		nor->addr_width = 4;
>>  	} else {
>>  		nor->addr_width = 3;
>>  	}
>>  
>> +	if (nor->addr_width == 3 && nor->mtd.size > 0x1000000) {
> Nitpick:    ^^^^^^^^^^^^^^^^^^^^^^^^ you can drop this part. But its 
> fine either way.
> 

I don't think its a good idea to drop nor->addr_width == 3 check as
nor->info->addr_width is permitted to have a value > 4 (although there
is no such flash today)...

> Reviewed-by: Pratyush Yadav <p.yadav@...com>
> 
>> +		/* enable 4-byte addressing if the device exceeds 16MiB */
>> +		nor->addr_width = 4;
>> +	}
>> +
>>  	if (nor->addr_width > SPI_NOR_MAX_ADDR_WIDTH) {
>>  		dev_dbg(nor->dev, "address width is too large: %u\n",
>>  			nor->addr_width);
> 

Regards
Vignesh