Re: [RFC PATCH 2/2] mtd: spi-nor: Disable the flash quad mode in spi_nor_restore()

[Pratyush Yadav <me@xxxxxxxxxxxxxxxxx>]

Hi Yicong,

On 24/04/20 05:20PM, Yicong Yang wrote:
> If the flash's quad mode is enabled, it'll remain in the quad mode when
> it's removed. If we drive the flash next time in SPI/Dual mode, then
> problem occurs as the flash's quad enable bit is not cleared.
> 
> Disable the quad mode in spi_nor_restore(), the flash will leave
> quad mode when remove. This will make sure the flash always enter the
> correct mode when loaded.
> 
> Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
> ---
>  drivers/mtd/spi-nor/core.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index d0516e8..611c0b7 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -3001,6 +3001,11 @@ void spi_nor_restore(struct spi_nor *nor)
>  	if (nor->addr_width == 4 && !(nor->flags & SNOR_F_4B_OPCODES) &&
>  	    nor->flags & SNOR_F_BROKEN_RESET)
>  		nor->params->set_4byte_addr_mode(nor, false);
> +
> +	/* disable quad mode */
> +	if (spi_nor_get_protocol_width(nor->read_proto) == 4 ||
> +	    spi_nor_get_protocol_width(nor->write_proto) == 4)
> +		nor->params->quad_enable(nor, false);

If a flash doesn't have a quad enable function, this will lead to a NULL 
pointer access. Please use spi_nor_quad_enable() instead.

>  }
>  EXPORT_SYMBOL_GPL(spi_nor_restore);

-- 
Regards,
Pratyush Yadav

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