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

Maxime Ripard
2015-02-16T20:58:25Z

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Hi Robert,

On Mon, Feb 16, 2015 at 09:11:24PM +0100, Robert Jarzmik wrote:
> 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.

That's very true that this driver would need some love, but
valentine's day was last week.

I'm sorry, but this is a patch targeted for stable. This is a pure
bugfix. I won't rewrite the whole driver solely to make the driver
better, especially since that would make such a patch (or more likely
a whole serie) unsuitable for stable.

Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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