# \[PATCH\] viafb: correct sync polarity for OLPC DCON

- Subsystems: FRAMEBUFFER LAYER, THE REST
- Maintainers: Helge Deller, Linus Torvalds
- List: linux-fbdev
- 2 messages, 2 authors
- Page: https://ratatoskr.run/linux-fbdev/2011/11/13462146/t

## \[PATCH\] viafb: correct sync polarity for OLPC DCON

- From: Daniel Drake \<hidden\>
- Date: 2011-11-21 15:05:56 
- Message: https://ratatoskr.run/linux-fbdev/2011/11/13462146.md

```text
While the OLPC display appears to be able to handle either positive
or negative sync, the Display Controller only recognises positive sync.

This brings viafb (for XO-1.5) in line with lxfb (for XO-1) and
fixes a recent regression where the XO-1.5 DCON could no longer be
frozen. Thanks to Florian Tobias Schandinat for helping identify
the fix.

Test case: from a vt,
	echo 1 > /sys/devices/platform/dcon/freeze
should cause the current screen contents to freeze, rather than garbage being
displayed.

Signed-off-by: Daniel Drake <redacted>
---
 drivers/video/via/share.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/via/share.h b/drivers/video/via/share.h
index 69d882c..c01c1c1 100644
--- a/drivers/video/via/share.h
+++ b/drivers/video/via/share.h
@@ -559,8 +559,8 @@
 #define M1200X720_R60_VSP       POSITIVE
 
 /* 1200x900@60 Sync Polarity (DCON) */
-#define M1200X900_R60_HSP       NEGATIVE
-#define M1200X900_R60_VSP       NEGATIVE
+#define M1200X900_R60_HSP       POSITIVE
+#define M1200X900_R60_VSP       POSITIVE
 
 /* 1280x600@60 Sync Polarity (GTF Mode) */
 #define M1280x600_R60_HSP       NEGATIVE
-- 
1.7.7.3

```

## Re: \[PATCH\] viafb: correct sync polarity for OLPC DCON

- From: Florian Tobias Schandinat \<FlorianSchandinat@gmx.de\>
- Date: 2011-11-23 06:53:42 
- Message: https://ratatoskr.run/linux-fbdev/2011/11/13462147.md

```text
On 11/21/2011 03:05 PM, Daniel Drake wrote:
> While the OLPC display appears to be able to handle either positive
> or negative sync, the Display Controller only recognises positive sync.
> 
> This brings viafb (for XO-1.5) in line with lxfb (for XO-1) and
> fixes a recent regression where the XO-1.5 DCON could no longer be
> frozen. Thanks to Florian Tobias Schandinat for helping identify
> the fix.
> 
> Test case: from a vt,
> 	echo 1 > /sys/devices/platform/dcon/freeze
> should cause the current screen contents to freeze, rather than garbage being
> displayed.
> 
> Signed-off-by: Daniel Drake <redacted>

Applied.


Thanks,

Florian Tobias Schandinat

> ---
>  drivers/video/via/share.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/via/share.h b/drivers/video/via/share.h
> index 69d882c..c01c1c1 100644
> --- a/drivers/video/via/share.h
> +++ b/drivers/video/via/share.h
> @@ -559,8 +559,8 @@
>  #define M1200X720_R60_VSP       POSITIVE
>  
>  /* 1200x900@60 Sync Polarity (DCON) */
> -#define M1200X900_R60_HSP       NEGATIVE
> -#define M1200X900_R60_VSP       NEGATIVE
> +#define M1200X900_R60_HSP       POSITIVE
> +#define M1200X900_R60_VSP       POSITIVE
>  
>  /* 1280x600@60 Sync Polarity (GTF Mode) */
>  #define M1280x600_R60_HSP       NEGATIVE

```