Re: [PATCH] fbdev/ffb: fix corrupted video output on FFB1

[Helge Deller <deller@gmx.de>]

Hello Rene,

On 2/5/26 16:49, René Rebe wrote:
> Fix Sun FFB1 corrupted video out [1] by disabling overlay and
> initializing window mode to a known state. The issue never appeared on
> my FFB2+/vertical nor Elite3D/M6. It could also depend on the PROM
> version.
> 
> /SUNW,ffb@1e,0: FFB at 000001fc00000000, type 11, DAC pnum[236c] rev[10] manuf_rev[4]
> X (II) /dev/fb0: Detected FFB1, Z-buffer, Single-buffered.
> X (II) /dev/fb0: BT9068 (PAC1) ramdac detected (with normal cursor control)
> X (II) /dev/fb0: Detected Creator/Creator3D
> 
> [1] https://www.instagram.com/p/DUTcSmSjSem/

The patch itself seems ok.
But could you please link to a freely accessible website instead of Instagram?
I and many others don't have (and don't want) an instagram account, so
the link is not very useful.

Helge
  
> Signed-off-by: René Rebe <rene@exactco.de>
> Cc: stable@kernel.org
> ---
> Tested on Sun Ultra 2 w/ FFB1 BT9068 (PAC1) ramdac running T2/Linux.
> Defines re-used from xf86-video-sunffb.
> ---
> diff --git a/drivers/video/fbdev/ffb.c b/drivers/video/fbdev/ffb.c
> index 34b6abff9493..8d77f102dd82 100644
> --- a/drivers/video/fbdev/ffb.c
> +++ b/drivers/video/fbdev/ffb.c
> @@ -335,6 +335,9 @@ struct ffb_dac {
>   };
>   
>   #define FFB_DAC_UCTRL		0x1001 /* User Control */
> +#define FFB_DAC_UCTRL_OVENAB	0x00000008 /* Overlay Enable */
> +#define FFB_DAC_UCTRL_WMODE	0x00000030 /* Window Mode */
> +#define FFB_DAC_UCTRL_WM_COMB	0x00000000 /* Window Mode = Combined */
>   #define FFB_DAC_UCTRL_MANREV	0x00000f00 /* 4-bit Manufacturing Revision */
>   #define FFB_DAC_UCTRL_MANREV_SHIFT 8
>   #define FFB_DAC_TGEN		0x6000 /* Timing Generator */
> @@ -425,7 +428,7 @@ static void ffb_switch_from_graph(struct ffb_par *par)
>   {
>   	struct ffb_fbc __iomem *fbc = par->fbc;
>   	struct ffb_dac __iomem *dac = par->dac;
> -	unsigned long flags;
> +	unsigned long flags, uctrl;
>   
>   	spin_lock_irqsave(&par->lock, flags);
>   	FFBWait(par);
> @@ -442,7 +445,7 @@ static void ffb_switch_from_graph(struct ffb_par *par)
>   	upa_writel(par->bg_cache, &fbc->bg);
>   	FFBWait(par);
>   
> -	/* Disable cursor.  */
> +	/* Disable cursor. */
>   	upa_writel(FFB_DAC_CUR_CTRL, &dac->type2);
>   	if (par->flags & FFB_FLAG_INVCURSOR)
>   		upa_writel(0, &dac->value2);
> @@ -450,6 +453,15 @@ static void ffb_switch_from_graph(struct ffb_par *par)
>   		upa_writel((FFB_DAC_CUR_CTRL_P0 |
>   			    FFB_DAC_CUR_CTRL_P1), &dac->value2);
>   
> +	/* Disable overlay and window modes. */
> +	upa_writel(FFB_DAC_UCTRL, &dac->type);
> +	uctrl = upa_readl(&dac->value);
> +	uctrl &= ~FFB_DAC_UCTRL_WMODE;
> +	uctrl |= FFB_DAC_UCTRL_WM_COMB;
> +	uctrl &= ~FFB_DAC_UCTRL_OVENAB;
> +	upa_writel(FFB_DAC_UCTRL, &dac->type);
> +	upa_writel(uctrl, &dac->value);
> +
>   	spin_unlock_irqrestore(&par->lock, flags);
>   }
>   
>