Re: [PATCH 2/2] drm/i915: Add wait_for in init_ring_common

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, Mar 16, 2012 at 12:43:22PM -0400, Sean Paul wrote:
> I have seen a number of "blt ring initialization failed" messages
> where the ctl or start registers are not the correct value. Upon further
> inspection, if the code just waited a little bit, it would read the
> correct value. Adding the wait_for to these reads should eliminate the
> issue.
> 
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 8357822..d95f0f9 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -298,9 +298,9 @@ static int init_ring_common(struct intel_ring_buffer *ring)
>  			| RING_REPORT_64K | RING_VALID);
>  
>  	/* If the head is still not zero, the ring is dead */
> -	if ((I915_READ_CTL(ring) & RING_VALID) == 0 ||
> -	    I915_READ_START(ring) != obj->gtt_offset ||
> -	    (I915_READ_HEAD(ring) & HEAD_ADDR) != 0) {
> +	if (wait_for((I915_READ_CTL(ring) & RING_VALID) != 0 &&
> +		     I915_READ_START(ring) == obj->gtt_offset &&
> +		     (I915_READ_HEAD(ring) & HEAD_ADDR) == 0, 50)) {
>  		DRM_ERROR("%s initialization failed "
>  				"ctl %08x head %08x tail %08x start %08x\n",
>  				ring->name,
> -- 
> 1.7.7.3
> 
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