Re: [PATCH 4/6] drm/i915/vga: Include the current pipe in the VGA disable debug message

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 17 Apr 2025, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Add some debugs to the VGA plane disable so that we can at least
> see from the logs when it happens (and on which pipe). I was curious
> about this at some point when I was seeing some random underruns
> near the time when we disable the VGA plane, but I think in the end
> that turned out to be a red herring.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_vga.c | 29 +++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vga.c b/drivers/gpu/drm/i915/display/intel_vga.c
> index 56047f701798..7ee689a9da92 100644
> --- a/drivers/gpu/drm/i915/display/intel_vga.c
> +++ b/drivers/gpu/drm/i915/display/intel_vga.c
> @@ -12,6 +12,7 @@
>  #include "i915_drv.h"
>  #include "i915_reg.h"
>  #include "intel_de.h"
> +#include "intel_display.h"
>  #include "intel_vga.h"
>  #include "intel_vga_regs.h"
>  
> @@ -25,16 +26,42 @@ static i915_reg_t intel_vga_cntrl_reg(struct intel_display *display)
>  		return VGACNTRL;
>  }
>  
> +static bool has_vga_pipe_sel(struct intel_display *display)
> +{
> +	if (display->platform.i845g ||
> +	    display->platform.i865g)
> +		return false;
> +
> +	if (display->platform.valleyview ||
> +	    display->platform.cherryview)
> +		return true;
> +
> +	return DISPLAY_VER(display) < 7;
> +}
> +
>  /* Disable the VGA plane that we never use */
>  void intel_vga_disable(struct intel_display *display)
>  {
>  	struct pci_dev *pdev = to_pci_dev(display->drm->dev);
>  	i915_reg_t vga_reg = intel_vga_cntrl_reg(display);
> +	enum pipe pipe;
> +	u32 tmp;
>  	u8 sr1;
>  
> -	if (intel_de_read(display, vga_reg) & VGA_DISP_DISABLE)
> +	tmp = intel_de_read(display, vga_reg);
> +	if (tmp & VGA_DISP_DISABLE)
>  		return;
>  
> +	if (display->platform.cherryview)
> +		pipe = REG_FIELD_GET(VGA_PIPE_SEL_MASK_CHV, tmp);
> +	else if (has_vga_pipe_sel(display))
> +		pipe = REG_FIELD_GET(VGA_PIPE_SEL_MASK, tmp);
> +	else
> +		pipe = PIPE_A;
> +
> +	drm_dbg_kms(display->drm, "Disabling VGA plane on pipe %c\n",
> +		    pipe_name(pipe));
> +
>  	/* WaEnableVGAAccessThroughIOPort:ctg,elk,ilk,snb,ivb,vlv,hsw */
>  	vga_get_uninterruptible(pdev, VGA_RSRC_LEGACY_IO);
>  	outb(0x01, VGA_SEQ_I);

-- 
Jani Nikula, Intel