Re: [PATCH v4 1/2] mtd: nand: pxa3xx: Fix PIO FIFO draining

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Wed, 18 Feb 2015 11:32:07 +0100
Maxime Ripard <maxime.ripard@free-electrons.com> wrote:

> The NDDB register holds the data that are needed by the read and write
> commands.
> 
> However, during a read PIO access, the datasheet specifies that after each 32
> bytes read in that register, when BCH is enabled, we have to make sure that the
> RDDREQ bit is set in the NDSR register.
> 
> This fixes an issue that was seen on the Armada 385, and presumably other mvebu
> SoCs, when a read on a newly erased page would end up in the driver reporting a
> timeout from the NAND.
> 
> Cc: <stable@vger.kernel.org> # v3.14
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> ---
>  drivers/mtd/nand/pxa3xx_nand.c | 48 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 42 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
> index 96b0b1d27df1..bc677362bc73 100644
> --- a/drivers/mtd/nand/pxa3xx_nand.c
> +++ b/drivers/mtd/nand/pxa3xx_nand.c
> @@ -480,6 +480,42 @@ static void disable_int(struct pxa3xx_nand_info *info, uint32_t int_mask)
>  	nand_writel(info, NDCR, ndcr | int_mask);
>  }
>  
> +static void drain_fifo(struct pxa3xx_nand_info *info, void *data, int len)
> +{
> +	if (info->ecc_bch) {
> +		int timeout;
> +
> +		/*
> +		 * According to the datasheet, when reading from NDDB
> +		 * with BCH enabled, after each 32 bytes reads, we
> +		 * have to make sure that the NDSR.RDDREQ bit is set.
> +		 *
> +		 * Drain the FIFO 8 32 bits reads at a time, and skip
> +		 * the polling on the last read.
> +		 */
> +		while (len > 8) {
> +			__raw_readsl(info->mmio_base + NDDB, data, 8);
> +
> +			for (timeout = 0;
> +			     !(nand_readl(info, NDSR) & NDSR_RDDREQ);
> +			     timeout++) {
> +				if (timeout >= 5) {
> +					dev_err(&info->pdev->dev,
> +						"Timeout on RDDREQ while draining the FIFO\n");
> +					return;
> +				}
> +
> +				mdelay(1);
> +			}
> +
> +			data += 32;
> +			len -= 8;
> +		}
> +	}
> +
> +	__raw_readsl(info->mmio_base + NDDB, data, len);
> +}
> +
>  static void handle_data_pio(struct pxa3xx_nand_info *info)
>  {
>  	unsigned int do_bytes = min(info->data_size, info->chunk_size);
> @@ -496,14 +532,14 @@ static void handle_data_pio(struct pxa3xx_nand_info *info)
>  				      DIV_ROUND_UP(info->oob_size, 4));
>  		break;
>  	case STATE_PIO_READING:
> -		__raw_readsl(info->mmio_base + NDDB,
> -			     info->data_buff + info->data_buff_pos,
> -			     DIV_ROUND_UP(do_bytes, 4));
> +		drain_fifo(info,
> +			   info->data_buff + info->data_buff_pos,
> +			   DIV_ROUND_UP(do_bytes, 4));
>  
>  		if (info->oob_size > 0)
> -			__raw_readsl(info->mmio_base + NDDB,
> -				     info->oob_buff + info->oob_buff_pos,
> -				     DIV_ROUND_UP(info->oob_size, 4));
> +			drain_fifo(info,
> +				   info->oob_buff + info->oob_buff_pos,
> +				   DIV_ROUND_UP(info->oob_size, 4));
>  		break;
>  	default:
>  		dev_err(&info->pdev->dev, "%s: invalid state %d\n", __func__,



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com