Re: [PATCH V3] Add support for flag status register on Micron chips.

[Huang Shijie]

On Tue, Apr 22, 2014 at 09:03:16AM -0500, Graham Moore wrote:
> Some new Micron flash chips require reading the flag
> status register to determine when operations have completed.
> 
> Furthermore, chips with multi-die stacks of the 65nm 256Mb QSPI also
> require reading the status register before reading the flag status register.
> 
> This patch adds support for the flag status register in the n25q512ax3 and n25q00
> Micron QSPI flash chips.
> 
> Signed-off-by: Graham Moore <grmoore@xxxxxxxxxx>
> ---
> V3:
> Rebase to l2-mtd spinor branch.
> V2:
> Remove leading underscore in function names.
> Remove type cast in dev_err call and use the proper format
> specifier instead.
> ---
>  drivers/mtd/spi-nor/spi-nor.c |   51 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/mtd/spi-nor.h   |    4 ++++
>  2 files changed, 55 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index d6f44d5..24b84d8 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -48,6 +48,25 @@ static int read_sr(struct spi_nor *nor)
>  }
>  
>  /*
> + * Read the flag status register, returning its value in the location
> + * Return the status register value.
> + * Returns negative if error occurred.
> + */
> +static int read_fsr(struct spi_nor *nor)
> +{
> +	int ret;
> +	u8 val;
> +
> +	ret = nor->read_reg(nor, SPINOR_OP_RDFSR, &val, 1);
> +	if (ret < 0) {
> +		pr_err("error %d reading FSR\n", ret);
> +		return ret;
> +	}
> +
> +	return val;
> +}
> +
> +/*
>   * Read configuration register, returning its value in the
>   * location. Return the configuration register value.
>   * Returns negative if error occured.
> @@ -165,6 +184,32 @@ static int spi_nor_wait_till_ready(struct spi_nor *nor)
>  	return -ETIMEDOUT;
>  }
>  
> +static int spi_nor_wait_till_fsr_ready(struct spi_nor *nor)
> +{
> +	unsigned long deadline;
> +	int sr;
> +	int fsr;
> +
> +	deadline = jiffies + MAX_READY_WAIT_JIFFIES;
> +
> +	do {
> +		cond_resched();
> +
> +		sr = read_sr(nor);
> +		if (sr < 0)
> +			break;
> +		else if (!(sr & SR_WIP)) {
> +			fsr = read_fsr(nor);
> +			if (fsr < 0)
> +				break;
> +			if (fsr & FSR_READY)
> +				return 0;			
> +		}
> +	} while (!time_after_eq(jiffies, deadline));
> +
> +	return -ETIMEDOUT;
> +}
> +
>  /*
>   * Service routine to read status register until ready, or timeout occurs.
>   * Returns non-zero if error.
> @@ -402,6 +447,7 @@ struct flash_info {
>  #define	SECT_4K_PMC		0x10	/* SPINOR_OP_BE_4K_PMC works uniformly */
>  #define	SPI_NOR_DUAL_READ	0x20    /* Flash supports Dual Read */
>  #define	SPI_NOR_QUAD_READ	0x40    /* Flash supports Quad Read */
> +#define	USE_FSR			0x80	/* use flag status register */
>  };
>  
>  #define INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags)	\
> @@ -488,6 +534,8 @@ const struct spi_device_id spi_nor_ids[] = {
>  	{ "n25q128a13",  INFO(0x20ba18, 0, 64 * 1024,  256, 0) },
>  	{ "n25q256a",    INFO(0x20ba19, 0, 64 * 1024,  512, SECT_4K) },
>  	{ "n25q512a",    INFO(0x20bb20, 0, 64 * 1024, 1024, SECT_4K) },
> +	{ "n25q512ax3",  INFO(0x20ba20, 0, 64 * 1024, 1024, USE_FSR) },
> +	{ "n25q00",      INFO(0x20ba21, 0, 64 * 1024, 2048, USE_FSR) },
>  
>  	/* PMC */
>  	{ "pm25lv512",   INFO(0,        0, 32 * 1024,    2, SECT_4K_PMC) },
> @@ -965,6 +1013,9 @@ int spi_nor_scan(struct spi_nor *nor, const struct spi_device_id *id,
>  	else
>  		mtd->_write = spi_nor_write;
>  
> +	if (info->flags & USE_FSR)
> +		nor->wait_till_ready = spi_nor_wait_till_fsr_ready;
> +
the drivers may fills this hook itself, so the code should like this:
   --------------------------------------------------
	if ((info->flags & USE_FSR) &&
	       	nor->wait_till_ready == spi_nor_wait_till_fsr_ready)
		nor->wait_till_ready = spi_nor_wait_till_fsr_ready;
   --------------------------------------------------


thanks
Huang Shijie
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