[U-Boot] [PATCH 2/2] serial: bcm283x_mu: Detect disabled serial device

[Simon Glass]

Hi Alex,

On 11 August 2016 at 05:38, Alexander Graf <agraf at suse.de> wrote:
> On the raspberry pi, you can disable the serial port to gain dynamic frequency
> scaling which can get handy at times.
>
> However, in such a configuration the serial controller gets its rx queue filled
> up with zero bytes which then happily get transmitted on to whoever calls
> getc() today.
>
> This patch adds detection logic for that case by checking whether the RX pin is
> mapped to GPIO15 and disables the mini uart if it is not mapped properly.
>
> That way we can leave the driver enabled in the tree and can determine during
> runtime whether serial is usable or not, having a single binary that allows for
> uart and non-uart operation.
>
> Signed-off-by: Alexander Graf <agraf at suse.de>
>
> ---
>
> v2 -> v3:
>
>   - Disable and detect pinmux in board file
> ---
>  board/raspberrypi/rpi/rpi.c | 29 +++++++++++++++++++++++++++++
>  configs/rpi_3_32b_defconfig |  1 +
>  configs/rpi_3_defconfig     |  1 +
>  include/configs/rpi.h       |  1 +
>  4 files changed, 32 insertions(+)
>
> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
> index 4c8253d..20b0d1b 100644
> --- a/board/raspberrypi/rpi/rpi.c
> +++ b/board/raspberrypi/rpi/rpi.c
> @@ -453,6 +453,35 @@ int board_init(void)
>         return power_on_module(BCM2835_MBOX_POWER_DEVID_USB_HCD);
>  }
>
> +static bool rpi_is_serial_active(void)
> +{
> +#ifndef CONFIG_PL01X_SERIAL
> +       int serial_gpio = 15;
> +       struct udevice *dev;
> +
> +       /*
> +        * The RPi3 disables the mini uart by default. The easiest way to find
> +        * out whether it is available is to check if the pin is muxed.
> +        */
> +       if (uclass_first_device(UCLASS_GPIO, &dev) || !dev)
> +               return true;
> +
> +       if (bcm2835_gpio_get_func_id(dev, serial_gpio) != BCM2835_GPIO_ALT5)
> +               return false;

Do you mean gpio_get_function()?


> +#endif
> +
> +       return true;
> +}
> +
> +int board_late_init(void)
> +{
> +       /* Disable mini-UART I/O if it's not pinmuxed to our pins */
> +       if (!rpi_is_serial_active())
> +               gd->cur_serial_dev = NULL;
> +
> +       return 0;
> +}
> +
>  int board_mmc_init(bd_t *bis)
>  {
>         ALLOC_CACHE_ALIGN_BUFFER(struct msg_get_clock_rate, msg_clk, 1);
> diff --git a/configs/rpi_3_32b_defconfig b/configs/rpi_3_32b_defconfig
> index 922e01b..4c2f106 100644
> --- a/configs/rpi_3_32b_defconfig
> +++ b/configs/rpi_3_32b_defconfig
> @@ -20,3 +20,4 @@ CONFIG_CMD_FAT=y
>  CONFIG_CMD_FS_GENERIC=y
>  CONFIG_PHYS_TO_BUS=y
>  CONFIG_OF_LIBFDT=y
> +# CONFIG_REQUIRE_SERIAL_CONSOLE is not set
> diff --git a/configs/rpi_3_defconfig b/configs/rpi_3_defconfig
> index bff92df..288214c 100644
> --- a/configs/rpi_3_defconfig
> +++ b/configs/rpi_3_defconfig
> @@ -19,3 +19,4 @@ CONFIG_CMD_FAT=y
>  CONFIG_CMD_FS_GENERIC=y
>  CONFIG_PHYS_TO_BUS=y
>  CONFIG_OF_LIBFDT=y
> +# CONFIG_REQUIRE_SERIAL_CONSOLE is not set
> diff --git a/include/configs/rpi.h b/include/configs/rpi.h
> index b5543f4..e3b890a 100644
> --- a/include/configs/rpi.h
> +++ b/include/configs/rpi.h
> @@ -22,6 +22,7 @@
>
>  /* Architecture, CPU, etc.*/
>  #define CONFIG_ARCH_CPU_INIT
> +#define CONFIG_BOARD_LATE_INIT
>
>  /* Use SoC timer for AArch32, but architected timer for AArch64 */
>  #ifndef CONFIG_ARM64
> --
> 1.8.5.6
>

Regards,
Simon