linux-kernel - Re: [PATCH v4 09/20] mtd: spi-nor: Drop spansion_quad

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Message-ID: <1547a4b2-b279-ab4c-0b2c-cd88df219b4a@ti.com>
Date:   Tue, 5 Nov 2019 18:05:37 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     <Tudor.Ambarus@...rochip.com>, <boris.brezillon@...labora.com>
CC:     <miquel.raynal@...tlin.com>, <richard@....at>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 09/20] mtd: spi-nor: Drop spansion_quad_enable()



On 02/11/19 4:53 PM, Tudor.Ambarus@...rochip.com wrote:
> From: Tudor Ambarus <tudor.ambarus@...rochip.com>
> 
> Drop the default spansion_quad_enable() method and replace it with
> spansion_read_cr_quad_enable().
> 
> The function was buggy, it didn't care about the previous values
> of the Status and Configuration Registers. spansion_read_cr_quad_enable()
> is a Read-Modify-Write-Check function that keeps track of what were
> the previous values of the Status and Configuration Registers.
> 
> In terms of instruction types sent to the flash, the only difference
> between the spansion_quad_enable() and spansion_read_cr_quad_enable()
> is that the later calls spi_nor_read_sr(). We can safely assume that all
> flashes support spi_nor_read_sr(), because all flashes call it in
> spi_nor_sr_ready(). The transition from spansion_quad_enable() to
> spansion_read_cr_quad_enable() will not affect anybody, drop the buggy
> code.
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>

Reviewed-by: Vignesh Raghavendra <vigneshr@...com>

Regards
Vignesh

> ---
>  drivers/mtd/spi-nor/spi-nor.c | 58 ++++---------------------------------------
>  1 file changed, 5 insertions(+), 53 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 99a9a6aba41d..f5193733a0f6 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -1971,54 +1971,6 @@ static int macronix_quad_enable(struct spi_nor *nor)
>  }
>  
>  /**
> - * spansion_quad_enable() - set QE bit in Configuraiton Register.
> - * @nor:	pointer to a 'struct spi_nor'
> - *
> - * Set the Quad Enable (QE) bit in the Configuration Register.
> - * This function is kept for legacy purpose because it has been used for a
> - * long time without anybody complaining but it should be considered as
> - * deprecated and maybe buggy.
> - * First, this function doesn't care about the previous values of the Status
> - * and Configuration Registers when it sets the QE bit (bit 1) in the
> - * Configuration Register: all other bits are cleared, which may have unwanted
> - * side effects like removing some block protections.
> - * Secondly, it uses the Read Configuration Register (35h) instruction though
> - * some very old and few memories don't support this instruction. If a pull-up
> - * resistor is present on the MISO/IO1 line, we might still be able to pass the
> - * "read back" test because the QSPI memory doesn't recognize the command,
> - * so leaves the MISO/IO1 line state unchanged, hence spi_nor_read_cr() returns
> - * 0xFF.
> - *
> - * bit 1 of the Configuration Register is the QE bit for Spansion like QSPI
> - * memories.
> - *
> - * Return: 0 on success, -errno otherwise.
> - */
> -static int spansion_quad_enable(struct spi_nor *nor)
> -{
> -	u8 *sr_cr = nor->bouncebuf;
> -	int ret;
> -
> -	sr_cr[0] = 0;
> -	sr_cr[1] = CR_QUAD_EN_SPAN;
> -	ret = spi_nor_write_sr(nor, sr_cr, 2);
> -	if (ret)
> -		return ret;
> -
> -	/* read back and check it */
> -	ret = spi_nor_read_cr(nor, nor->bouncebuf);
> -	if (ret)
> -		return ret;
> -
> -	if (!(nor->bouncebuf[0] & CR_QUAD_EN_SPAN)) {
> -		dev_dbg(nor->dev, "Spansion Quad bit not set\n");
> -		return -EINVAL;
> -	}
> -
> -	return 0;
> -}
> -
> -/**
>   * spansion_no_read_cr_quad_enable() - set QE bit in Configuration Register.
>   * @nor:	pointer to a 'struct spi_nor'
>   *
> @@ -2170,9 +2122,9 @@ static int spi_nor_clear_sr_bp(struct spi_nor *nor)
>   *
>   * Read-modify-write function that clears the Block Protection bits from the
>   * Status Register without affecting other bits. The function is tightly
> - * coupled with the spansion_quad_enable() function. Both assume that the Write
> - * Register with 16 bits, together with the Read Configuration Register (35h)
> - * instructions are supported.
> + * coupled with the spansion_read_cr_quad_enable() function. Both assume that
> + * the Write Register with 16 bits, together with the Read Configuration
> + * Register (35h) instructions are supported.
>   *
>   * Return: 0 on success, -errno otherwise.
>   */
> @@ -4654,7 +4606,7 @@ static void spi_nor_info_init_params(struct spi_nor *nor)
>  	u8 i, erase_mask;
>  
>  	/* Initialize legacy flash parameters and settings. */
> -	params->quad_enable = spansion_quad_enable;
> +	params->quad_enable = spansion_read_cr_quad_enable;
>  	params->set_4byte = spansion_set_4byte;
>  	params->setup = spi_nor_default_setup;
>  
> @@ -4869,7 +4821,7 @@ static int spi_nor_init(struct spi_nor *nor)
>  	int err;
>  
>  	if (nor->clear_sr_bp) {
> -		if (nor->params.quad_enable == spansion_quad_enable)
> +		if (nor->params.quad_enable == spansion_read_cr_quad_enable)
>  			nor->clear_sr_bp = spi_nor_spansion_clear_sr_bp;
>  
>  		err = nor->clear_sr_bp(nor);
> 

-- 
Regards
Vignesh