[U-Boot] [BUG] display_options() fails on Raspberry Pi 3B+

[Matthias Brugger]

Hi Heinrich,

adding Alex just in case he knows better, as he wrote the initial code.

On 06/11/2019 01:57, Heinrich Schuchardt wrote:
> Hello Matthias,
> 
> Tom reported:
> 
> Since patch
> 143256b353c4d2ad1cf5e5e63b38410188b35e49
> fdt: update bcm283x device tree sources to Linux 5.1-rc6 state
> 
> the console no longer shows the initial message, e.g. "U-Boot
> 2020.01-rc1-00159-g73b6e6ad25-dirty". This leads to a failure in
> automated testing.
> 
> To find out what is happening I applied the following code change:
> 
> diff --git a/drivers/serial/serial_bcm283x_mu.c
> b/drivers/serial/serial_bcm283x_mu.c
> index bd1d89ec83..395c49c60a 100644
> --- a/drivers/serial/serial_bcm283x_mu.c
> +++ b/drivers/serial/serial_bcm283x_mu.c
> @@ -171,8 +171,11 @@ static int
> bcm283x_mu_serial_ofdata_to_platdata(struct udevice *dev)
>         fdt_addr_t addr;
> 
>         /* Don't spawn the device if it's not muxed */
> -       if (!bcm283x_is_serial_muxed())
> +       if (!bcm283x_is_serial_muxed()) {
> +               sprintf((void *)0x02400000, "muxed4 false\n");
>                 return -ENODEV;
> +       }
> +       sprintf((void *)0x02400010, "muxed5 true");
> 
>         addr = devfdt_get_addr(dev);
>         if (addr == FDT_ADDR_T_NONE)
> diff --git a/lib/display_options.c b/lib/display_options.c
> index ec16d75e0e..9d44f49731 100644
> --- a/lib/display_options.c
> +++ b/lib/display_options.c
> @@ -45,6 +45,7 @@ int display_options(void)
> 
>         display_options_get_banner(true, buf, sizeof(buf));
>         printf("%s", buf);
> +       sprintf((void *)0x02400009, "disp5options");
> 
>         return 0;
>  }
> 
> 
> And see:
> 
> 02400000: 6d 75 78 65 64 34 20 66 61 64 69 73 70 35 6f 70    muxed4
> fadisp5op
> 02400010: 6d 75 78 65 64 35 20 74 72 75 65 00 05 07 06 01    muxed5
> true.....
> 
> bcm283x_mu_serial_ofdata_to_platdata() is obviously called twice.
> 
> The first call is in serial_init(). At that time the GPIOs are not
> correctly set up to use the serial port. So display_options() fails.
> After relocation another call call occurs after the GPIOs are set up and
> this call succeeds.
> 
> Do you have an idea how to proceed?
> 

After digging a bit, my guess is: in the mentioned devicetree commit you change
the stdout-path from serial0 (pl011) to serial1 (aux-uart).

My guess is, that the FW sets the pin mux to ALT0 which leads
bcm283x_is_serial_muxed() to fail.

I wasn't able to find where the pinctrl is initialized. Shouldn't that happen
before we call serial_init()?

Regards,
Matthias