Re: [PATCH 3/6] drm/i915: Error out if we are trying to use VGA with SPLL already in use

[Ben Widawsky <ben@bwidawsk.net>]

On Thu, Mar 07, 2013 at 03:30:25PM +0000, Damien Lespiau wrote:
> Our static analysis tool noticed that 'reg' could be used uninitialized if
> we are trying to get a PLL to drive VGA and SPLL is already in use
> (plls->spll_refcoung != 0).
> 
> In the (error) case above, let's return false to the caller and emit an
> error.
> 
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index a1505e3..0eab200 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -898,6 +898,9 @@ bool intel_ddi_pll_mode_set(struct drm_crtc *crtc, int clock)
>  			plls->spll_refcount++;
>  			reg = SPLL_CTL;
>  			intel_crtc->ddi_pll_sel = PORT_CLK_SEL_SPLL;
> +		} else {
> +			DRM_ERROR("SPLL already in use\n");
> +			return false;
>  		}
>  
>  		WARN(I915_READ(reg) & SPLL_PLL_ENABLE,

I know very little about this code, but the warning still seems valuable
to me.

How about instead of else, move the reg = SPLL_CTL above the 'if'

-- 
Ben Widawsky, Intel Open Source Technology Center