[PATCH 2/3] drm/komeda - At init write GCU control block to handle already on DPU

[Liviu Dudau]

On Mon, Jun 06, 2022 at 12:47:13PM +0100, carsten.haitzler at foss.arm.com wrote:
> From: Carsten Haitzler <carsten.haitzler at arm.com>
> 
> If something has already set up the DPU before the komeda driver comes
> up, it will fail to init because it was just writing to the SRST bit in
> the GCU control register and ignoring others. This resulted in TBU
> bringup stalling and init failing. By writing completely we also  set the
> mode back to 0 (inactive) too and thus TBU bringup works.

This is a rather large hammer, tbh. I would like to see if there is a better way of
handling the handover from EFIFB that this patch is trying to fix, but I lack an
usable plaform for that. It will generate a flicker at module load time, but if users
of Morello are happy with that, then

Acked-by: Liviu Dudau <liviu.dudau at arm.com>

Best regards,
Liviu

> 
> Signed-off-by: Carsten Haitzler <carsten.haitzler at arm.com>
> ---
>  drivers/gpu/drm/arm/display/komeda/d71/d71_dev.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_dev.c b/drivers/gpu/drm/arm/display/komeda/d71/d71_dev.c
> index 00fa56c29b3e..39618c1a4c81 100644
> --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_dev.c
> +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_dev.c
> @@ -309,8 +309,7 @@ static int d71_reset(struct d71_dev *d71)
>  	u32 __iomem *gcu = d71->gcu_addr;
>  	int ret;
>  
> -	malidp_write32_mask(gcu, BLK_CONTROL,
> -			    GCU_CONTROL_SRST, GCU_CONTROL_SRST);
> +	malidp_write32(gcu, BLK_CONTROL, GCU_CONTROL_SRST);
>  
>  	ret = dp_wait_cond(!(malidp_read32(gcu, BLK_CONTROL) & GCU_CONTROL_SRST),
>  			   100, 1000, 10000);
> -- 
> 2.32.0
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯