Re: spi-ar934x: Using GPIO CS issue

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Dave,

On Thu, Nov 4, 2021 at 3:58 PM Dave Bender <codehero@gmail.com> wrote:
> On Thu, Nov 4, 2021 at 5:50 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > Does it work if you change GPIO_ACTIVE_LOW to GPIO_ACTIVE_HIGH?
>
>   There is a pullup resistor on that CS line, so that GPIO must be active low.

I do believe you.  But there's been some issues with inverted CS
gpio behavior when switching from board files to DT, so I thought
I'd better ask to try...

>   Digging deeper into the code, it looks like David Bauer made some
> changes that limit the spi driver's CS usage to only the CS0, CS1, CS2
> pins.
>   There is also no bounds checking on the CS value.
>   I don't understand how this driver can even use generic GPIO if it
> forces use of the CS bits on the SPI_IOC register.

OK, that sounds like a reasonable culprit...

>
> static int ar934x_spi_transfer_one_message(struct spi_controller *master,
>              struct spi_message *m)
> {
>    ....
>    ....
>     for (trx_done = 0; trx_done < t->len; trx_done += 4) {
>
>    .....
>       reg = AR934X_SPI_SHIFT_VAL(spi->chip_select, term,
>                trx_cur * 8);
>       iowrite32(reg, sp->base + AR934X_SPI_REG_SHIFT_CTRL);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds