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

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Date:   Wed, 7 Oct 2020 13:18:38 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     Vignesh Raghavendra <vigneshr@...com>
CC:     Bert Vermeulen <bert@...t.com>, <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 07/10/20 12:59PM, Vignesh Raghavendra wrote:
> 
> 
> 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)...

The check below for SPI_NOR_MAX_ADDR_WIDTH will return an error when 
nor->addr_width > 4, but I see your point.
 
> > 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

-- 
Regards,
Pratyush Yadav
Texas Instruments India