Re: [PATCH] spi: xilinx: Inhibit transmitter while filling TX FIFO

[Ricardo Ribalda Delgado <ribalda@xxxxxxxxxx>]

Hi Jonathan

On Sat, May 8, 2021 at 4:45 AM Jonathan Lemon <jonathan.lemon@xxxxxxxxx> wrote:
>
> On 7 May 2021, at 17:46, Jonathan Lemon wrote:
>
> > On 7 May 2021, at 16:02, Ricardo Ribalda Delgado wrote:
> >
> >> Hi Jonathan
> >>
> >> Thanks for your patch.
> >>
> >> On Fri, May 7, 2021 at 11:53 PM Jonathan Lemon
> >> <jonathan.lemon@xxxxxxxxx> wrote:
> >>>
> >>> Contrary to the comment in xilinx_spi_txrx_bufs(), the transmitter
> >>> was not disabled on entry.  On my particular board, when sending a
> >>> PP
> >>> sequence, the first address byte was clocked out 3 times, writing
> >>> data
> >>> into the wrong location, and generally locking up the chip.
> >>
> >> Sorry, what do you mean by PP sequence?
> >>
> >> By clocked out 3 times you mean that the sequence is sent like
> >> B0........B1.........B2
> >> instead of:
> >> B0B1B2
> >
> > PP: Page program.  When I’m trying to write to the flash, the
> > sequence
> > [opcode 02][A1 A2 A3][D1 D2 ..] is sent.  The result is a flash write
> > at location [A1 A1 A1] = [A2 A3 D1 D2 ...]
> >
> > In other words, the first byte of the address appears to have been
> > sent to the chip 3x.
> >
> >
> >> If your hardware supports IRQ. can you try forcing use_irq to true?
> >
> > Will try this in a bit.  The hw does have an irq registered, but it
> > it isn't always set, as it depends on how many how many bytes the
> > spi_transfer sets.  So sometimes it will set use_irq, and sometimes
> > not.
>
> So I tried the following change:
>
> -       if (xspi->irq >= 0 &&  remaining_words > xspi->buffer_size) {
> +       if (xspi->irq >= 0) {
>
> And that also allows writes to to through successfully.   Perhaps
> this is a simpler change that would work?

It was just a test... we do not want to disable the non-irq mode,
because for small operations it is much faster.

I think this probes that it might be a timming issue. I would really
like to see the output from your logic analyser/chipscope/

Thanks :)

> --
> Jonathan