Re: [PATCH v2] mtd: rawnand: marvell: check for RDY bits after enabling the IRQ

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Mon, 1 Oct 2018 22:01:27 +0000
Chris Packham <Chris.Packham@alliedtelesis.co.nz> wrote:

> On 02/10/18 10:41, Boris Brezillon wrote:
> > On Mon, 1 Oct 2018 22:34:38 +0200
> > Boris Brezillon <boris.brezillon@bootlin.com> wrote:
> >      
> >>>
> >>> I'd previously tried readl() based on the same hunch. No change.
> >>>
> >>> I think my snippet above might be misleading. While a delay between
> >>> readl_relaxed() and the if should not change the outcome, this is also a
> >>> delay between marvell_nfc_enable_int() and marvell_nfc_disable_int()
> >>> which is probably more significant. Sure enough if I move the delay to
> >>> just before the marvell_nfc_disable_int() the error is not seen.  
> >>
> >> AFAICT, your timeout always happens when waiting for RDREQ, not RDYM.
> >> So maybe disabling MRDY too early has a side-effect on the RDREQ event.  
> > 
> > Can you try with this patch [1]? It should ensure that NDSR_RDY bits
> > are cleared before starting an operation.
> > 
> > [1]http://code.bulix.org/lgs30c-468205
> >   
> 
> No luck. I applied that on top of Daniel's and got the same result.
> 
> One thing that does look promising is the following modification of 
> Daniel's patch[1]. Which moves the RDY check to before where the 
> interrupts are enabled.

Except we still don't know why this is happening, and I'm not sure I
want to take a fix without understanding why it does fix the problem.

Also, it looks like complete() is not called until the RDDREQ, WRDREQ
and WRCMDREQ are cleared in the interrupt handler [1], which is weird.
Miquel, do you happen to remember why you had to do that?

[1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mtd/nand/raw/marvell_nand.c?h=v4.19-rc6#n689