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

["Grant Likely" <grant.likely@secretlab.ca>]

On Thu, Mar 20, 2008 at 8:43 AM, 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 addressing.  As a result,
>  it is not compatible with the open firmware 'ns16550' compatible
>  binding.
>
>  This code adds the Xilinx uart 16550 to the serial console
>  of the boot. A new initialization function for the Xilinx 16550 uart
>  is added to the ns16550 driver. It sets up the correct register base
>  and regshift properties specific to the Xilinx 16550.
>
>  Signed-off-by: John Linn <john.linn@xilinx.com>
>  ---
>   arch/powerpc/boot/ns16550.c |   24 ++++++++++++++++++++++++
>   arch/powerpc/boot/ops.h     |    1 +
>   arch/powerpc/boot/serial.c  |    8 ++++++++
>   3 files changed, 33 insertions(+), 0 deletions(-)
>
>  diff --git a/arch/powerpc/boot/ns16550.c b/arch/powerpc/boot/ns16550.c
>  index f8f1b2f..5385255 100644
>  --- a/arch/powerpc/boot/ns16550.c
>  +++ b/arch/powerpc/boot/ns16550.c
>  @@ -77,3 +77,27 @@ int ns16550_console_init(void *devp, struct serial_console_data *scdp)
>
>         return 0;
>   }
>  +
>  +int xilinx16550_console_init(void *devp, struct serial_console_data *scdp)
>  +{
>  +       int n;
>  +       unsigned long reg_phys;
>  +
>  +       n = getprop(devp, "virtual-reg", &reg_base, sizeof(reg_base));
>  +       if (n != sizeof(reg_base)) {
>  +               if (!dt_xlate_reg(devp, 0, &reg_phys, NULL))
>  +                       return -1;
>  +
>  +               reg_base = (void *)reg_phys + 3;
>  +       }
>  +
>  +       reg_shift = 2;
>  +
>  +       scdp->open = ns16550_open;
>  +       scdp->putc = ns16550_putc;
>  +       scdp->getc = ns16550_getc;
>  +       scdp->tstc = ns16550_tstc;
>  +       scdp->close = NULL;
>  +
>  +       return 0;

This is mostly duplicated code.  xilinx16550_console_init should
simply call ns16550_console_init and then modify reg_base/reg_shift
after it returns.

However, if something like sparse16550 is used, then the need for this
function disappears.  In fact, ns16550_console_init already supports
the reg-shift property.  It just doesn't know about the 3 byte offset.

Cheers,
g.



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.