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

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

Hi Boris,

Boris Brezillon <boris.brezillon@xxxxxxxxxxx> wrote on Tue, 2 Oct 2018
00:13:28 +0200:

> On Mon, 1 Oct 2018 22:01:27 +0000
> Chris Packham <Chris.Packham@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> > On 02/10/18 10:41, Boris Brezillon wrote:  
> > > On Mon, 1 Oct 2018 22:34:38 +0200
> > > Boris Brezillon <boris.brezillon@xxxxxxxxxxx> 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?

The RDDREQ, WRDREQ and WRCMDREQ events might potentially happen while
the interrupts are enabled while we only wait for R/B signalling. This
check is to avoid calling complete() on these situations.

> 
> [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


Thanks,
Miquèl

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