linux-kernel - Re: [PATCH 1/3] mtd: spi-nor: sst: fix write support for SST

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Message-ID: <dc80d00a-27a3-6c75-5820-97ad2e297d8e@ti.com>
Date:   Mon, 14 Sep 2020 17:30:38 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Marco Felsch <m.felsch@...gutronix.de>,
        <tudor.ambarus@...rochip.com>, <miquel.raynal@...tlin.com>,
        <richard@....at>, <sergei.shtylyov@...entembedded.com>,
        <boris.brezillon@...labora.com>, <michael@...le.cc>,
        <j.neuschaefer@....net>
CC:     <linux-mtd@...ts.infradead.org>, <kernel@...gutronix.de>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mtd: spi-nor: sst: fix write support for SST_WRITE
 marked devices



On 9/11/20 8:17 PM, Marco Felsch wrote:
> The sst write support for devices using the special SST_WRITE routine
> is broken since commit commit df5c21002cf4 ("mtd: spi-nor: use spi-mem
> dirmap API") because the spi_nor_create_write_dirmap() function checks
> SPINOR_OP_AAI_WP and sst_write_second. These checks are not valid during
> probe. The check seems also to be broken since the "op->addr.nbytes = 0"
> causes the devm_spi_mem_dirmap_create() function to return
> PTR_ERR(-EINVAL) and the probe() function will fail.
> 
> It seems that the commit only copy'n'pasted the existing logic. Use the
> correct SST_WRITE flag and return 0 to fix both issues.
> 
> Fixes: df5c21002cf4 ("mtd: spi-nor: use spi-mem dirmap API")
> Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> ---
>  drivers/mtd/spi-nor/core.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 65eff4ce6ab1..31869ac245a8 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -3289,15 +3289,21 @@ static int spi_nor_create_write_dirmap(struct spi_nor *nor)
>  	};
>  	struct spi_mem_op *op = &info.op_tmpl;
>  
> +	/*
> +	 * Most SST SPI-NOR's have a special write routine.which should so

s/SPI-NOR/SPI NOR.

> +	 * dirmap.wdesc is not supported for these.

Or How about more readable version:

"Most SST flashes have special sequence for writing data to the flash
and therefore cannot support writes through direct mapping APIs."

> +	 */
> +	if (nor->info->flags & SST_WRITE) {
> +		nor->dirmap.wdesc = NULL;

nor->dirmap.wdesc is known to be NULL at this point. So no need to set
to NULL again.

> +		return 0;
> +	}
> +
>  	/* get transfer protocols. */
>  	op->cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->write_proto);
>  	op->addr.buswidth = spi_nor_get_protocol_addr_nbits(nor->write_proto);
>  	op->dummy.buswidth = op->addr.buswidth;
>  	op->data.buswidth = spi_nor_get_protocol_data_nbits(nor->write_proto);
>  
> -	if (nor->program_opcode == SPINOR_OP_AAI_WP && nor->sst_write_second)
> -		op->addr.nbytes = 0;
> -
>  	nor->dirmap.wdesc = devm_spi_mem_dirmap_create(nor->dev, nor->spimem,
>  						       &info);
>  	return PTR_ERR_OR_ZERO(nor->dirmap.wdesc);
>