[U-Boot] [PATCH v2 2/2] bcm283x_pl011: Flush RX queue after setting baud rate

[Peter Robinson]

On Wed, Mar 7, 2018 at 9:08 PM, Alexander Graf <agraf at suse.de> wrote:
> After the UART was initialized, we may still have bogus data in the
> RX queue if it was enabled with incorrect pin muxing before.
>
> So let's flush the RX queue whenever we initialize baud rates.
>
> This fixes a regression with the dynamic pinmuxing code when enable_uart=1
> is not set in config.txt on Raspberry Pis that use pl011 for serial.
>
> Fixes: caf2233b28 ("bcm283x: Add pinctrl driver")
> Reported-by: Göran Lundberg <goran at lundberg.email>
> Reported-by: Peter Robinson <pbrobinson at gmail.com>
> Signed-off-by: Alexander Graf <agraf at suse.de>
Tested-by: Peter Robinson <pbrobinson at gmail.com>

Tested on RPi2 and works a lot better, I can boot, interact with the
console etc :-)


> ---
>
> v1 -> v2:
>
>   - correctly drain the queue
> ---
>  drivers/serial/serial_bcm283x_pl011.c  | 25 ++++++++++++++++++++++++-
>  drivers/serial/serial_pl01x.c          | 10 +++++-----
>  drivers/serial/serial_pl01x_internal.h |  7 ++++++-
>  3 files changed, 35 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/serial/serial_bcm283x_pl011.c b/drivers/serial/serial_bcm283x_pl011.c
> index bfd39f84f3..dad7236895 100644
> --- a/drivers/serial/serial_bcm283x_pl011.c
> +++ b/drivers/serial/serial_bcm283x_pl011.c
> @@ -9,6 +9,7 @@
>  #include <asm/gpio.h>
>  #include <dm/pinctrl.h>
>  #include <dm/platform_data/serial_pl01x.h>
> +#include <serial.h>
>  #include "serial_pl01x_internal.h"
>
>  /*
> @@ -55,6 +56,28 @@ static int bcm283x_pl011_serial_ofdata_to_platdata(struct udevice *dev)
>         return 0;
>  }
>
> +static int bcm283x_pl011_serial_setbrg(struct udevice *dev, int baudrate)
> +{
> +       int r;
> +
> +       r = pl01x_serial_setbrg(dev, baudrate);
> +
> +       /*
> +        * We may have been muxed to a bogus line before. Drain the RX
> +        * queue so we start at a clean slate.
> +        */
> +       while (pl01x_serial_getc(dev) != -EAGAIN) ;
> +
> +       return r;
> +}
> +
> +static const struct dm_serial_ops bcm283x_pl011_serial_ops = {
> +       .putc = pl01x_serial_putc,
> +       .pending = pl01x_serial_pending,
> +       .getc = pl01x_serial_getc,
> +       .setbrg = bcm283x_pl011_serial_setbrg,
> +};
> +
>  static const struct udevice_id bcm283x_pl011_serial_id[] = {
>         {.compatible = "brcm,bcm2835-pl011", .data = TYPE_PL011},
>         {}
> @@ -67,7 +90,7 @@ U_BOOT_DRIVER(bcm283x_pl011_uart) = {
>         .ofdata_to_platdata = of_match_ptr(bcm283x_pl011_serial_ofdata_to_platdata),
>         .platdata_auto_alloc_size = sizeof(struct pl01x_serial_platdata),
>         .probe  = pl01x_serial_probe,
> -       .ops    = &pl01x_serial_ops,
> +       .ops    = &bcm283x_pl011_serial_ops,
>         .flags  = DM_FLAG_PRE_RELOC,
>         .priv_auto_alloc_size = sizeof(struct pl01x_priv),
>  };
> diff --git a/drivers/serial/serial_pl01x.c b/drivers/serial/serial_pl01x.c
> index 23d9d839cb..45f1282770 100644
> --- a/drivers/serial/serial_pl01x.c
> +++ b/drivers/serial/serial_pl01x.c
> @@ -273,7 +273,7 @@ __weak struct serial_device *default_serial_console(void)
>
>  #ifdef CONFIG_DM_SERIAL
>
> -static int pl01x_serial_setbrg(struct udevice *dev, int baudrate)
> +int pl01x_serial_setbrg(struct udevice *dev, int baudrate)
>  {
>         struct pl01x_serial_platdata *plat = dev_get_platdata(dev);
>         struct pl01x_priv *priv = dev_get_priv(dev);
> @@ -299,21 +299,21 @@ int pl01x_serial_probe(struct udevice *dev)
>                 return 0;
>  }
>
> -static int pl01x_serial_getc(struct udevice *dev)
> +int pl01x_serial_getc(struct udevice *dev)
>  {
>         struct pl01x_priv *priv = dev_get_priv(dev);
>
>         return pl01x_getc(priv->regs);
>  }
>
> -static int pl01x_serial_putc(struct udevice *dev, const char ch)
> +int pl01x_serial_putc(struct udevice *dev, const char ch)
>  {
>         struct pl01x_priv *priv = dev_get_priv(dev);
>
>         return pl01x_putc(priv->regs, ch);
>  }
>
> -static int pl01x_serial_pending(struct udevice *dev, bool input)
> +int pl01x_serial_pending(struct udevice *dev, bool input)
>  {
>         struct pl01x_priv *priv = dev_get_priv(dev);
>         unsigned int fr = readl(&priv->regs->fr);
> @@ -324,7 +324,7 @@ static int pl01x_serial_pending(struct udevice *dev, bool input)
>                 return fr & UART_PL01x_FR_TXFF ? 0 : 1;
>  }
>
> -const struct dm_serial_ops pl01x_serial_ops = {
> +static const struct dm_serial_ops pl01x_serial_ops = {
>         .putc = pl01x_serial_putc,
>         .pending = pl01x_serial_pending,
>         .getc = pl01x_serial_getc,
> diff --git a/drivers/serial/serial_pl01x_internal.h b/drivers/serial/serial_pl01x_internal.h
> index c56dd54c7b..d4605f24a3 100644
> --- a/drivers/serial/serial_pl01x_internal.h
> +++ b/drivers/serial/serial_pl01x_internal.h
> @@ -43,7 +43,12 @@ struct pl01x_regs {
>
>  int pl01x_serial_ofdata_to_platdata(struct udevice *dev);
>  int pl01x_serial_probe(struct udevice *dev);
> -extern const struct dm_serial_ops pl01x_serial_ops;
> +
> +/* Needed for external pl01x_serial_ops drivers */
> +int pl01x_serial_putc(struct udevice *dev, const char ch);
> +int pl01x_serial_pending(struct udevice *dev, bool input);
> +int pl01x_serial_getc(struct udevice *dev);
> +int pl01x_serial_setbrg(struct udevice *dev, int baudrate);
>
>  struct pl01x_priv {
>         struct pl01x_regs *regs;
> --
> 2.12.3
>