Subject: [PATCH v1 2/7] mtd: spi-nor: add DDR quad read support

From: [email-masked] (Marek Vasut)
Date: Wed, 23 Apr 2014 21:45:57 +0200

On Wednesday, April 23, 2014 at 12:16:50 PM, Huang Shijie wrote:
> This patch adds the DDR quad read support by the following:
> 
>   [1] add SPI_NOR_DDR_QUAD read mode.
> 
>   [2] add DDR Quad read opcodes:
>        SPINOR_OP_READ_1_4_4_D / SPINOR_OP_READ4_1_4_4_D
> 
>   [3] add set_ddr_quad_mode() to initialize for the DDR quad read.
>       Currently it only works for Spansion NOR.
> 
>   [3] set the dummy with 8 for DDR quad read.
>       The m25p80.c can not support the DDR quad read, the SPI NOR
> controller can set the dummy value in its driver, such as fsl-quadspi.c.
> 
> Test this patch for Spansion s25fl128s NOR flash.
> 
> Signed-off-by: Huang Shijie <[email-masked]>
> ---
>  drivers/mtd/spi-nor/spi-nor.c |   50
> +++++++++++++++++++++++++++++++++++++++- include/linux/mtd/spi-nor.h   |  
>  8 +++++-
>  2 files changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 1a12f81..e2f69db 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -74,6 +74,15 @@ static int read_cr(struct spi_nor *nor)
>  static inline int spi_nor_read_dummy_cycles(struct spi_nor *nor)
>  {
>  	switch (nor->flash_read) {
> +	case SPI_NOR_DDR_QUAD:
> +		/*
> +		 * The m25p80.c can not support the DDR quad read.
> +		 * We set the dummy cycles to 8 by default. If the SPI NOR
> +		 * controller driver has already set it before call the
> +		 * spi_nor_scan(), we just keep it as it is.
> +		 */
> +		if (nor->read_dummy)
> +			return nor->read_dummy;

Can the controller set this variable to zero ?

[...]

> +static int set_ddr_quad_mode(struct spi_nor *nor, u32 jedec_id)
> +{
> +	int status;
> +
> +	switch (JEDEC_MFR(jedec_id)) {
> +	case CFI_MFR_AMD: /* Spansion, actually */
> +		status = spansion_quad_enable(nor);
> +		if (status) {
> +			dev_err(nor->dev,
> +				"Spansion DDR quad-read not enabled\n");
> +			return -EINVAL;

Can't you just return status here as well to propagate the failure?
[...]