Subject: Re: [PATCH 19/23] mtd: spi-nor: Rework spansion(_no)_read_cr_quad_enable()

From: Vignesh Raghavendra <[email-masked]>
Date: Thu, 19 Sep 2019 23:04:15 +0530

On 17-Sep-19 9:25 PM, [email-masked] wrote:
> From: Tudor Ambarus <[email-masked]>
> 
> Merge:
> spansion_no_read_cr_quad_enable()
> spansion_read_cr_quad_enable()
> 
> in spi_nor_sr2_bit1_quad_enable().
> 
> Avoid duplication of code by using spi_nor_write_16bit_sr_and_check(),
> the SNOR_F_NO_READ_CR case is treated there.
> 
> We now do the Read Back test even for the old
> spansion_no_read_cr_quad_enable() case.
> 
> Signed-off-by: Tudor Ambarus <[email-masked]>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 89 ++++++++++---------------------------------
>  include/linux/mtd/spi-nor.h   |  4 +-
>  2 files changed, 22 insertions(+), 71 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 2f79923e7db5..8648666fb9bd 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -907,7 +907,7 @@ static int spi_nor_write_16bit_sr_and_check(struct spi_nor *nor, u8 status_new,
>  		 * Write Status (01h) command is available just for the cases
>  		 * in which the QE bit is described in SR2 at BIT(1).
>  		 */
> -		sr_cr[1] = CR_QUAD_EN_SPAN;
> +		sr_cr[1] = SR2_QUAD_EN_BIT1;
>  	} else {
>  		sr_cr[1] = 0;
>  	}
> @@ -1963,81 +1963,34 @@ static int spi_nor_sr1_bit6_quad_enable(struct spi_nor *nor)
>  }
>  
>  /**
> - * spansion_no_read_cr_quad_enable() - set QE bit in Configuration Register.
> + * spi_nor_sr2_bit1_quad_enable() - set the Quad Enable BIT(1) in the Status
> + * Register 2.
>   * @nor:	pointer to a 'struct spi_nor'
>   *
> - * Set the Quad Enable (QE) bit in the Configuration Register.
> - * This function should be used with QSPI memories not supporting the Read
> - * Configuration Register (35h) instruction.
> - *
> - * bit 1 of the Configuration Register is the QE bit for Spansion like QSPI
> - * memories.
> - *
> - * Return: 0 on success, -errno otherwise.
> - */
> -static int spansion_no_read_cr_quad_enable(struct spi_nor *nor)
> -{
> -	u8 *sr_cr = nor->bouncebuf;
> -	int ret;
> -
> -	/* Keep the current value of the Status Register. */
> -	ret = spi_nor_read_sr(nor, &sr_cr[0]);
> -	if (ret)
> -		return ret;
> -
> -	sr_cr[1] = CR_QUAD_EN_SPAN;
> -
> -	return spi_nor_write_sr(nor, sr_cr, 2);
> -}
> -
> -/**
> - * spansion_read_cr_quad_enable() - set QE bit in Configuration Register.
> - * @nor:	pointer to a 'struct spi_nor'
> - *
> - * Set the Quad Enable (QE) bit in the Configuration Register.
> - * This function should be used with QSPI memories supporting the Read
> - * Configuration Register (35h) instruction.
> - *
> - * bit 1 of the Configuration Register is the QE bit for Spansion like QSPI
> - * memories.
> + * Bit 1 of the Status Register 2 is the QE bit for Spansion like QSPI memories.
>   *
>   * Return: 0 on success, -errno otherwise.
>   */
> -static int spansion_read_cr_quad_enable(struct spi_nor *nor)
> +static int spi_nor_sr2_bit1_quad_enable(struct spi_nor *nor)
>  {
> -	u8 *sr_cr = nor->bouncebuf;
>  	int ret;
>  
> -	/* Check current Quad Enable bit value. */
> -	ret = spi_nor_read_cr(nor, &sr_cr[1]);
> -	if (ret)
> -		return ret;
> -
> -	if (sr_cr[1] & CR_QUAD_EN_SPAN)
> -		return 0;
> +	if (!(nor->flags & SNOR_F_NO_READ_CR)) {
> +		/* Check current Quad Enable bit value. */
> +		ret = spi_nor_read_cr(nor, &nor->bouncebuf[0]);
> +		if (ret)
> +			return ret;
>  
> -	sr_cr[1] |= CR_QUAD_EN_SPAN;
> +		if (nor->bouncebuf[0] & SR2_QUAD_EN_BIT1)
> +			return 0;
> +	}
>  
>  	/* Keep the current value of the Status Register. */
> -	ret = spi_nor_read_sr(nor, &sr_cr[0]);
> -	if (ret)
> -		return ret;
> -
> -	ret = spi_nor_write_sr(nor, sr_cr, 2);
> -	if (ret)
> -		return ret;
> -
> -	/* Read back and check it. */
> -	ret = spi_nor_read_cr(nor, &sr_cr[1]);
> +	ret = spi_nor_read_sr(nor, &nor->bouncebuf[0]);
>  	if (ret)
>  		return ret;
>  
> -	if (!(sr_cr[1] & CR_QUAD_EN_SPAN)) {
> -		dev_err(nor->dev, "Spansion Quad bit not set\n");
> -		return -EIO;
> -	}
> -
> -	return 0;

You need to set QE bit here before writing to CR register. This function
does not do that.

> +	return spi_nor_write_16bit_sr_and_check(nor, nor->bouncebuf[0], 0xFF);

Neither does spi_nor_write_16bit_sr_and_check().
We need a function that allows to modify SR2/CR register content as well
so as to set QE bit right?

Regards
Vignesh

>  }
>  
>  /**
> @@ -2117,7 +2070,7 @@ 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_read_cr_quad_enable() function. Both assume that
> + * coupled with the spi_nor_sr2_bit1_quad_enable() function. Both assume that
>   * the Write Register with 16 bits, together with the Read Configuration
>   * Register (35h) instructions are supported.
>   *
> @@ -2138,7 +2091,7 @@ static int spi_nor_spansion_clear_sr_bp(struct spi_nor *nor)
>  	 * When the configuration register Quad Enable bit is one, only the
>  	 * Write Status (01h) command with two data bytes may be used.
>  	 */
> -	if (sr_cr[1] & CR_QUAD_EN_SPAN) {
> +	if (sr_cr[1] & SR2_QUAD_EN_BIT1) {
>  		ret = spi_nor_read_sr(nor, &sr_cr[0]);
>  		if (ret)
>  			return ret;
> @@ -3642,7 +3595,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>  		 * supported.
>  		 */
>  		nor->flags |= SNOR_F_NO_READ_CR;
> -		flash->quad_enable = spansion_no_read_cr_quad_enable;
> +		flash->quad_enable = spi_nor_sr2_bit1_quad_enable;
>  		break;
>  
>  	case BFPT_DWORD15_QER_SR1_BIT6:
> @@ -3663,7 +3616,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>  		 * assumption of a 16-bit Write Status (01h) command.
>  		 */
>  		nor->flags |= SNOR_F_HAS_16BIT_SR;
> -		flash->quad_enable = spansion_read_cr_quad_enable;
> +		flash->quad_enable = spi_nor_sr2_bit1_quad_enable;
>  		break;
>  
>  	default:
> @@ -4626,7 +4579,7 @@ static void spi_nor_info_init_flash_params(struct spi_nor *nor)
>  	u8 i, erase_mask;
>  
>  	/* Initialize legacy flash parameters and settings. */
> -	flash->quad_enable = spansion_read_cr_quad_enable;
> +	flash->quad_enable = spi_nor_sr2_bit1_quad_enable;
>  	flash->set_4byte = spansion_set_4byte;
>  	flash->setup = spi_nor_default_setup;
>  	/* Default to 16-bit Write Status (01h) Command */
> @@ -4844,7 +4797,7 @@ static int spi_nor_init(struct spi_nor *nor)
>  	int err;
>  
>  	if (nor->clear_sr_bp) {
> -		if (nor->flash.quad_enable == spansion_read_cr_quad_enable)
> +		if (nor->flash.quad_enable == spi_nor_sr2_bit1_quad_enable)
>  			nor->clear_sr_bp = spi_nor_spansion_clear_sr_bp;
>  
>  		err = nor->clear_sr_bp(nor);
> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
> index 3a835de90b6a..5590a36eb43e 100644
> --- a/include/linux/mtd/spi-nor.h
> +++ b/include/linux/mtd/spi-nor.h
> @@ -144,10 +144,8 @@
>  #define FSR_P_ERR		BIT(4)	/* Program operation status */
>  #define FSR_PT_ERR		BIT(1)	/* Protection error bit */
>  
> -/* Configuration Register bits. */
> -#define CR_QUAD_EN_SPAN		BIT(1)	/* Spansion Quad I/O */
> -
>  /* Status Register 2 bits. */
> +#define SR2_QUAD_EN_BIT1	BIT(1)
>  #define SR2_QUAD_EN_BIT7	BIT(7)
>  
>  /* Supported SPI protocols */
> 

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