Re: [PATCH v3 1/2] mtd: nand: pxa3xx: Fix PIO FIFO draining

Robert Jarzmik
2015-02-16T20:11:56Z

Maxime Ripard <maxime.ripard@free-electrons.com> writes:

> drivers/mtd/nand/pxa3xx_nand.c | 47 ++++++++++++++++++++++++++++++++++++------
> 1 file changed, 41 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
> index 96b0b1d27df1..b2d8d6960765 100644
> --- a/drivers/mtd/nand/pxa3xx_nand.c
> +++ b/drivers/mtd/nand/pxa3xx_nand.c
> @@ -480,6 +480,41 @@ 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 index = 0;
> +
> + while (index < (len * 4)) {
> + u32 timeout;
> +
> + __raw_readsl(info->mmio_base + NDDB, data + index, 8);
> +
> + /*
> + * 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
> + */
> + 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);
So in worst case, we'll end up with 4 times mdelay(1) times len / 32.
For a 2048 page, it is : 256ms where everything is stuck (mdelay and not
msleep).

I know you had no choice because this is called from interrupt handler (top
half). But having a irq handler and a irq thread handler would solve that issue,
and you'll end up with msleep(1) in this code.

I don't think an mdelay(256) is acceptable.

Cheers.

--
Robert