Hi Daniel,
On Sun, Nov 14, 2010 at 02:12:31PM +0000, Daniel Drake wrote:
> Commit b5c26f97ec4a17c65 introduced some breakage for the OLPC XO-1 laptop,
> differences in the output video signal after the patch caused some problems
> with the XO's display controller chip.
>
> Reviewing of that commit against the AMD Geode LX Data Book, it seems
> that these bits were being set inversely. In both cases, active high
> output is denoted by a value of 0. See section 6.8.3.44 of the databook
> from February 2009 (Publication ID: 33234H)
>
I rechecked the Datasheet and it seems you are right with that.
But i don't like the logical mess in the statements. So here is what i
would prefer.
> Signed-off-by: Daniel Drake <dsd@xxxxxxxxxx>
> ---
> drivers/video/geode/lxfb_ops.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/geode/lxfb_ops.c b/drivers/video/geode/lxfb_ops.c
> index bc35a95..85ec7f6 100644
> --- a/drivers/video/geode/lxfb_ops.c
> +++ b/drivers/video/geode/lxfb_ops.c
> @@ -276,10 +276,10 @@ static void lx_graphics_enable(struct fb_info *info)
> write_fp(par, FP_PT1, 0);
> temp = FP_PT2_SCRC;
>
> - if (info->var.sync & FB_SYNC_HOR_HIGH_ACT)
> + if (!(info->var.sync & FB_SYNC_HOR_HIGH_ACT))
> temp |= FP_PT2_HSP;
Instead i would like to see something like this:
if (info->var.sync & FB_SYNC_HOR_HIGH_ACT)
temp &= ~(FP_PT2_HSP);
>
> - if (info->var.sync & FB_SYNC_VERT_HIGH_ACT)
> + if (!(info->var.sync & FB_SYNC_VERT_HIGH_ACT))
> temp |= FP_PT2_VSP;
if (info->var.sync & FB_SYNC_VERT_HIGH_ACT)
temp &= ~(FP_PT2_VSP);
>
> write_fp(par, FP_PT2, temp);
> --
> 1.7.3.2
So the meaning of the switch FB_SYNC_{HOR,VERT}_HIGH_ACT stays correct
for the user, but the commits on the register act as described in the
datasheet.
Regards,
Michael
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