On Thu, Sep 16, 2021 at 10:21:16AM +0000, Cheng, Xuzhou wrote:
> > diff --git a/hw/ssi/imx_spi.c b/hw/ssi/imx_spi.c
> > index 189423bb3a..7a093156bd 100644
> > --- a/hw/ssi/imx_spi.c
> > +++ b/hw/ssi/imx_spi.c
> > @@ -167,6 +167,8 @@ static void imx_spi_flush_txfifo(IMXSPIState *s)
> > DPRINTF("Begin: TX Fifo Size = %d, RX Fifo Size = %d\n",
> > fifo32_num_used(&s->tx_fifo), fifo32_num_used(&s->rx_fifo));
> >
> > + qemu_set_irq(s->cs_lines[imx_spi_selected_channel(s)], 0);
> > +
> > while (!fifo32_is_empty(&s->tx_fifo)) {
> > int tx_burst = 0;
> >
> > @@ -385,13 +387,6 @@ static void imx_spi_write(void *opaque, hwaddr
> > offset, uint64_t value,
> > case ECSPI_CONREG:
> > s->regs[ECSPI_CONREG] = value;
> >
> > - burst = EXTRACT(s->regs[ECSPI_CONREG], ECSPI_CONREG_BURST_LENGTH)
> > + 1;
> > - if (burst % 8) {
> > - qemu_log_mask(LOG_UNIMP,
> > - "[%s]%s: burst length %d not supported: rounding
> > up to next multiple of 8\n",
> > - TYPE_IMX_SPI, __func__, burst);
> > - }
> > -
> > if (!imx_spi_is_enabled(s)) {
> > /* device is disabled, so this is a soft reset */
> > imx_spi_soft_reset(s);
> > @@ -404,9 +399,11 @@ static void imx_spi_write(void *opaque, hwaddr
> > offset, uint64_t value,
> >
> > /* We are in master mode */
> >
> > - for (i = 0; i < ECSPI_NUM_CS; i++) {
> > - qemu_set_irq(s->cs_lines[i],
> > - i == imx_spi_selected_channel(s) ? 0 : 1);
> > + burst = EXTRACT(s->regs[ECSPI_CONREG],
> > ECSPI_CONREG_BURST_LENGTH);
> > + if (burst == 0) {
> > + for (i = 0; i < ECSPI_NUM_CS; i++) {
> > + qemu_set_irq(s->cs_lines[i], 1);
> > + }
> > }
>
> I got some free time in the past days to investigate this issue. Guenter is
> right, the Linux imx-spi driver does not work on QEMU.
>
> The reason is that the state of m25p80 machine loops in STATE_READING_DATA
> state after receiving RDSR command, the new command is ignored. Before
> sending a new command, the CS line should be pulled to high, this make the
> state of m25p80 back to IDLE.
>
> I have same point with Guenter, it's that set CS to 1 when burst is zero. But
> i don't think it is necessary to set CS to 0 in imx_spi_flush_txfifo(). I
> will send a new patch to fix this issue.
>
Thanks a lot for looking into this. If you have a better solution than mine, by
all means, please go for it. As I mentioned in my patch, I didn't really like
it, but I was unable to find a better solution.
> BTW, the Linux driver uses DMA mode when transfer length is greater than the
> FIFO size, But QEMU imx-spi model doesn't support DMA now.
Does it have practical impact ? Obviously my tests were somewhat limited (I was
happy to get Linux booting from flash), but I don't recall seeing a problem.
Thanks,
Guenter
