Hi Ezequiel,
On Mon, 2014-04-07 at 10:13 +0400, Alexey Brodkin wrote:
> Hi Ezequiel,
>
> On Fri, 2014-04-04 at 11:09 -0300, Ezequiel Garcia wrote:
> > On Apr 04, Alexey Brodkin wrote:
> > > Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
> > >
> >
> > Maybe it would be nice adding some driver description here, so the commit
> > log actually says something useful about the commit.
>
> Well, I thought about it but frankly I'm not sure if there's anything
> else to add to commit title "driver for NAND controller used on Synopsys
> AXS dev boards".
>
> Do you think more info may make sense?
>
> > > +/**
> > > + * axs_flag_wait_and_reset - Waits until requested flag in INT_STATUS register
> > > + * is set by HW and resets it by writing "1" in INT_CLR_STATUS.
> > > + * @host: Pointer to private data structure.
> > > + * @flag: Bit/flag offset in INT_STATUS register
> > > + */
> > > +static void axs_flag_wait_and_reset(struct axs_nand_host *host, int flag)
> > > +{
> > > + unsigned int i;
> > > +
> > > + for (i = 0; i < AXS_FLAG_WAIT_DELAY * 100; i++) {
> > > + unsigned int status = reg_get(host, INT_STATUS);
> > > +
> > > + if (status & (1 << flag)) {
> > > + reg_set(host, INT_CLR_STATUS, 1 << flag);
> > > + return;
> > > + }
> > > +
> > > + udelay(10);
> > > + }
> > > +
> > > + /*
> > > + * Since we cannot report this problem any further than
> > > + * axs_nand_{write|read}_buf() letting user know there's a problem.
> > > + */
> > > + dev_err(host->dev, "Waited too long (%d s.) for flag/bit %d\n",
> > > + AXS_FLAG_WAIT_DELAY, flag);
> > > +}
> >
> > Hm... I'm not sure the above is really true.
> >
> > The NAND core uses the replaceable chip->waitfunc callback to check the
> > status of issued commands. See for instance:
> >
> > static int nand_write_oob_std(struct mtd_info *mtd, struct nand_chip *chip,
> > int page)
> > {
> > int status = 0;
> > const uint8_t *buf = chip->oob_poi;
> > int length = mtd->oobsize;
> >
> > chip->cmdfunc(mtd, NAND_CMD_SEQIN, mtd->writesize, page);
> > chip->write_buf(mtd, buf, length);
> > /* Send command to program the OOB data */
> > chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
> >
> > status = chip->waitfunc(mtd, chip);
> >
> > return status & NAND_STATUS_FAIL ? -EIO : 0;
> > }
> >
> > On the other side, if you are clearing the flags in axs_flag_wait_and_reset()
> > it might be a bit hard for you to get this right.
> >
> > IOW, I'm not saying you *must* do this, but instead suggesting that you take
> > a look at waitfunc() and see if it helps report a proper error in the
> > read/write path.
>
> As I may understand from generic implementation of "waitfunc" in
> "nand_base.c" it checks status of NAND chip itself - which IMHO makes
> sense. And this is done via NAND_CMD_STATUS command sent to chip through
> NAND controller.
>
> In AXS NAND driver you may see 2 types of wait checks:
> 1. NAND_ISR_CMDDONE - this flag means that NAND controller has just
> executed provided command (i.e. set proper signal on control lines of
> NAND chip etc), but it doesn't mean NAND chip itself has completed
> command execution. That's why "waitfunc" is not direct replacement here.
>
> 2. NAND_ISR_{RX|TX}DMACOMPLETE - this flag indicates completion of DMA
> transfer to/from NAND chip to RAM. "waitfunc" won't work here as well.
>
> I hope this explanation makes sense.
Please treat this message as a gentle reminder.
I'm wondering if my explanation in the previous email makes any sense or
I still need to fix stuff.
Regards,
Alexey
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
