[OpenPower-Firmware] [PATCH V3] Update VGA Ownership register value.

[Joel Stanley]

On Tue, Jun 28, 2016 at 4:31 AM, Mamatha Inamdar
<mamatha4 at linux.vnet.ibm.com> wrote:
> Problem Description:
> Right now SCU2C: Control Register  values are not set correctly to enable VGA mode.
> SCU2C register value is set to 0x00041080, where bit 18, 17,16 and bit 7 are set
> to 1 which is CRT mode.
>
> Fix:
> To enable VGA mode we have to set all register bit values to default values ie VGA mode.
>
> 1)  bit 18 in SCU2C register is to select  the DVO source for display output,
>     by default it is VGA mode but it was set to 1(CRT mode).
>
>         18  RW Select the DVO source for display output
>         0: VGA mode (default)
>         1: Graphics CRT mode
>
> 2) bit 17 and 16 in SCU2C register is to select the DAC source for display output,
>     by default it is VGA mode but it was set to 1(CRT mode).
>         00: VGA mode
>         01: Grafics CRT mode
>         1X: pass-through DVO mode
>
> 2) second issue is  bit 7 in SCU2C register is to Enable 2D CRT Mode function as
>    below and it was set to 1 as CRT mode.
>
>         7 Enable 2D CRT Mode function
>         0: VGA mode (default)
>         1: CRT mode
>
> The new value of SCU2C register is updated with mask value ~0x70080, which will enable
> VGA mode by resetting bits 18,17,16 and 7 in SCU2C control register.

I wasn't sure as to the context of this change. Is this new value
something we want in the petitboot kernel for all systems?

If so, I will need Jeremy ack before including it.

Cheers,

Joel

>
> Signed-off-by: Mamatha Inamdar <mamatha4 at linux.vnet.ibm.com>
> ---
>  drivers/gpu/drm/ast/ast_post.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ast/ast_post.c b/drivers/gpu/drm/ast/ast_post.c
> index 703dba2..00ebe4f 100644
> --- a/drivers/gpu/drm/ast/ast_post.c
> +++ b/drivers/gpu/drm/ast/ast_post.c
> @@ -1681,7 +1681,7 @@ static void ast_init_output_control(struct drm_device *dev)
>                 break;
>         default:
>                 /* VGA only: enable DAC output */
> -               val &= ~0x30000;
> +               val &= ~0x70080;
>                 break;
>         }
>
>