[Intel-gfx] [PATCH 3/5] drm/i915/vlv: warn on bad VLV PLL divider values

[Chris Wilson]

On Fri, Sep 27, 2013 at 12:57:24PM -0700, Jesse Barnes wrote:
> This avoids a divide by zero and warns appropriately on this serious bug.
> 
> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 8da1c96..9a83236 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5109,6 +5109,11 @@ static void vlv_crtc_clock_get(struct intel_crtc *crtc,
>  	clock.p1 = (mdiv >> DPIO_P1_SHIFT) & 7;
>  	clock.p2 = (mdiv >> DPIO_P2_SHIFT) & 0x1f;
>  
> +	if (!clock.n || !(clock.p1 * clock.p2)) {

if ((clock.n & clock.p1 & clock.p2) == 0) {

or just

if (!clock.n || !clock.p1 || !clock.p2)

> +		WARN(1, "bad divider values on pipe %d\n", crtc->pipe);
> +		return;
> +	}
> +

So I think you want

if (WARN_ONCE(clock.n == 0 || clock.p1 == 0 || clock.p2 == 0,
              "bad divider values on pipe %d (m1=%d, m2=%d, p1=%d, p2=%d, n=%d)\n",
	      crtc->pipe, clock.m1, clock.m2, clock.p1, clock.p2, clock.n))
   return;
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre