[U-Boot] [PATCH] spi: fsl_qspi: Add controller busy check before new spi operation

[York Sun]

On 08/21/2017 03:25 AM, Suresh Gupta wrote:
> It is recommended to check either controller is free to take
> new spi action. The IP_ACC and AHB_ACC bits indicates that
> the controller is busy in IP or AHB mode respectively.
> And the BUSY bit indicates that the controller is currently
> busy handling a transaction to an external flash device
> 
> Signed-off-by: Suresh Gupta <suresh.gupta at nxp.com>
> ---
>   drivers/spi/fsl_qspi.c | 26 ++++++++++++++++++++++++++
>   drivers/spi/fsl_qspi.h |  4 ++++
>   2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/spi/fsl_qspi.c b/drivers/spi/fsl_qspi.c
> index 1dfa89a..69e9712 100644
> --- a/drivers/spi/fsl_qspi.c
> +++ b/drivers/spi/fsl_qspi.c
> @@ -165,6 +165,27 @@ static inline u32 qspi_endian_xchg(u32 data)
>   #endif
>   }
>   
> +static inline u32 qspi_controller_busy(struct fsl_qspi_priv *priv)
> +{
> +	u32 sr;
> +	u32 retry = 5;
> +
> +	do {
> +		sr = qspi_read32(priv->flags, &priv->regs->sr);
> +		if ((sr & QSPI_SR_BUSY_MASK) ||
> +		    (sr & QSPI_SR_AHB_ACC_MASK) ||
> +		    (sr & QSPI_SR_IP_ACC_MASK)) {
> +			debug("The controller is busy, sr = 0x%x\n", sr);
> +			udelay(1);
> +		} else {
> +			break;
> +		}
> +	} while (--retry);

Does the 5 microsecond-delay make any difference?

> +
> +	return (sr & QSPI_SR_BUSY_MASK) ||
> +		(sr & QSPI_SR_AHB_ACC_MASK) || (sr & QSPI_SR_IP_ACC_MASK);
> +}
> +
>   static void qspi_set_lut(struct fsl_qspi_priv *priv)
>   {
>   	struct fsl_qspi_regs *regs = priv->regs;
> @@ -765,6 +786,11 @@ int qspi_xfer(struct fsl_qspi_priv *priv, unsigned int bitlen,
>   
>   	WATCHDOG_RESET();
>   
> +	if (qspi_controller_busy(priv)) {
> +		printf("ERROR : The controller is busy\n");
> +		return -EBUSY;
> +	}

If the controller should never be busy for this operation, I wonder if 
you really need a delay above.

York