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

Maxime Ripard
2015-02-18T14:05:06Z

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On Wed, Feb 18, 2015 at 10:40:02AM -0300, Ezequiel Garcia wrote:
> On 02/18/2015 07:32 AM, Maxime Ripard 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>
> > ---
> > 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);
>
> This is probably a stupid nit.. but here it goes is it any
> difference if udelay is used here?
>
> Does this makes anything better/worse?

It doesn't make any difference. On the board I've been using, we never
hit the delay.

So I really don't care about the number of retries and the sleep
behind them. I made these numbers up, feel free to come up with others
if it makes you more comfortable, but could we settle this?

Thanks,
Maxime

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

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