Re: [PATCH 3/3][POWERPC][V2] Xilinx: boot support for Xilinx uart 16550.

["Johann Baudy" <johaahn@gmail.com>]

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Hi John,

I've a small question about ns16550 boot support.
I can't see any code related to either "clock-frequency" or "current-speed"
key words.
Such actions are performed in of_serial.c to get appropriate baud rate
(update of UART_DLL and UART_DLM).

Is it needed or is it a misunderstanding?
Personally, I have added this below debug code (dirty :)) to make it work.

diff --git a/arch/powerpc/boot/ns16550.c b/arch/powerpc/boot/ns16550.c
index f8f1b2f..850e223 100644
--- a/arch/powerpc/boot/ns16550.c
+++ b/arch/powerpc/boot/ns16550.c
@@ -26,6 +26,9 @@
 #define UART_MSR    6    /* In:  Modem Status Register */
 #define UART_SCR    7    /* I/O: Scratch Register */

+#define UART_LCR_DLAB 0x80      /* Divisor latch access */
+#define UART_LCR_8_DATA_BITS 0x03
+
 static unsigned char *reg_base;
 static u32 reg_shift;

@@ -56,6 +59,10 @@ int ns16550_console_init(void *devp, struct
serial_console_data *scdp)
 {
     int n;
     unsigned long reg_phys;
+  unsigned long divisor=0;
+  unsigned long spd=0, clk=0;
+
+

     n = getprop(devp, "virtual-reg", &reg_base, sizeof(reg_base));
     if (n != sizeof(reg_base)) {
@@ -75,5 +82,23 @@ int ns16550_console_init(void *devp, struct
serial_console_data *scdp)
     scdp->tstc = ns16550_tstc;
     scdp->close = NULL;

+    n = getprop(devp, "current-speed", &spd, sizeof(spd));
+
+
+    n = getprop(devp, "clock-frequency", &clk, sizeof(clk));
+
+
+  if(spd&&clk)
+  {
+
+     divisor = clk / (spd * 16UL);
+
+     out_8(reg_base + (UART_FCR << reg_shift), 0x06);
+     out_8(reg_base + (UART_LCR << reg_shift),
UART_LCR_8_DATA_BITS|UART_LCR_DLAB);
+     out_8(reg_base + (UART_DLL << reg_shift), divisor&0xff);
+     out_8(reg_base + (UART_DLM << reg_shift), (divisor>>8)&0xff);
+     out_8(reg_base + (UART_LCR << reg_shift), UART_LCR_8_DATA_BITS);
+
+  }
     return 0;

Best regards,
Johann

On Wed, Apr 2, 2008 at 4:52 PM, John Linn <john.linn@xilinx.com> wrote:

> The Xilinx 16550 uart core is not a standard 16550 because it uses
> word-based addressing rather than byte-based adressing. With
> additional properties it is compatible with the open firmware
> 'ns16550' compatible binding.
>
> This code updates the ns16550 driver to use the reg-offset property
> so that the Xilinx UART 16550 can be used with it. The reg-shift
> was already being handled.
>
> Signed-off-by: John Linn <john.linn@xilinx.com>
> ---
>  arch/powerpc/boot/ns16550.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/boot/ns16550.c b/arch/powerpc/boot/ns16550.c
> index f8f1b2f..da9d2c2 100644
> --- a/arch/powerpc/boot/ns16550.c
> +++ b/arch/powerpc/boot/ns16550.c
> @@ -56,6 +56,7 @@ int ns16550_console_init(void *devp, struct
> serial_console_data *scdp)
>  {
>        int n;
>        unsigned long reg_phys;
> +       u32 reg_offset;
>
>        n = getprop(devp, "virtual-reg", &reg_base, sizeof(reg_base));
>        if (n != sizeof(reg_base)) {
> @@ -65,6 +66,10 @@ int ns16550_console_init(void *devp, struct
> serial_console_data *scdp)
>                reg_base = (void *)reg_phys;
>        }
>
> +       n = getprop(devp, "reg-offset", &reg_offset, sizeof(reg_offset));
> +       if (n == sizeof(reg_offset))
> +               reg_base += reg_offset;
> +
>        n = getprop(devp, "reg-shift", &reg_shift, sizeof(reg_shift));
>        if (n != sizeof(reg_shift))
>                reg_shift = 0;
> --
> 1.5.2.1
>
>
>
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> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
>



-- 
Johann Baudy
johaahn@gmail.com

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