[PATCH] ARM: EXYNOS: autodetect enabled serial port in uncompress

[Kyungmin Park]

Hi,

On Tue, Apr 3, 2012 at 4:17 AM, Kukjin Kim <kgene.kim at samsung.com> wrote:
> From: Colin Cross <ccross at android.com>
>
> Check the ULCON register of each serial port to determine if
> it has been enabled by the bootloader.  If only one serial port
> is found enabled, use that one.  Otherwise, use the value from
> CONFIG_S3C_LOWLEVEL_UART_PORT.
>
> Signed-off-by: Colin Cross <ccross at android.com>
> Signed-off-by: Kukjin Kim <kgene.kim at samsung.com>
> ---
>  arch/arm/mach-exynos/include/mach/uncompress.h |   25 ++++++++++++++++++++++-
>  1 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mach-exynos/include/mach/uncompress.h b/arch/arm/mach-exynos/include/mach/uncompress.h
> index 2979995..0d17a43 100644
> --- a/arch/arm/mach-exynos/include/mach/uncompress.h
> +++ b/arch/arm/mach-exynos/include/mach/uncompress.h
> @@ -25,6 +25,25 @@ static unsigned int __raw_readl(unsigned int ptr)
>        return *((volatile unsigned int *)ptr);
>  }
>
> +static volatile u8 *exynos_autodetect_uart(volatile u8 *base)
> +{
> +       int i;
> +       int found = 0;
> +       int port;
> +
> +       for (i = 0; i < CONFIG_SERIAL_SAMSUNG_UARTS; i++) {
> +               if (__raw_readl((unsigned int)base + S3C_UART_OFFSET * i)) {
1. Even though ULCON has offset 0, it's better to add ULCON_OFFSET.
2. In our case, we disable the unused UART at bootloader except the
debug uart, then does it possible to read this value at kernel?
I think it's hang at here. So read it correctly it should enable the
required uart clock before read it.
3. As similar tegra, how about to read specific value from RX
register. e.g., 'D'?
> +                       port = i;
> +                       found++;
To match the description, it should brake at here. if not it detects
the last uart at several detected uarts.

BR,
kmpark
> +               }
> +       }
> +
> +       if (found != 1)
> +               port = CONFIG_S3C_LOWLEVEL_UART_PORT;
> +
> +       return base + S3C_UART_OFFSET * port;
> +}
> +
>  static void arch_detect_cpu(void)
>  {
>        u32 chip_id = __raw_readl(EXYNOS_PA_CHIPID);
> @@ -38,9 +57,11 @@ static void arch_detect_cpu(void)
>        chip_id &= 0xf;
>
>        if (chip_id == 0x5)
> -               uart_base = (volatile u8 *)EXYNOS5_PA_UART + (S3C_UART_OFFSET * CONFIG_S3C_LOWLEVEL_UART_PORT);
> +               uart_base = (volatile u8 *)EXYNOS5_PA_UART;
>        else
> -               uart_base = (volatile u8 *)EXYNOS4_PA_UART + (S3C_UART_OFFSET * CONFIG_S3C_LOWLEVEL_UART_PORT);
> +               uart_base = (volatile u8 *)EXYNOS4_PA_UART;
> +
> +       uart_base = exynos_autodetect_uart(uart_base);
>
>        /*
>         * For preventing FIFO overrun or infinite loop of UART console,
> --
> 1.7.2.3
>
> --
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