Re: [PATCH] drm/i915: Shift driver's HWSP usage out of reserved range

[Dave Gordon <david.s.gordon@intel.com>]

On 18/02/15 11:48, Thomas Daniel wrote:
> As of Gen6, the general purpose area of the hardware status page has shrunk and
> now begins at dword 0x30.  i915 driver uses dword 0x20 to store the seqno which
> is now reserved.  So shift our HWSP dwords up into the general purpose range
> before this bites us.
> 
> Signed-off-by: Thomas Daniel <thomas.daniel@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.h |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index b6c484f..39183fc 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -373,11 +373,12 @@ intel_write_status_page(struct intel_engine_cs *ring,
>   * 0x06: ring 2 head pointer (915-class)
>   * 0x10-0x1b: Context status DWords (GM45)
>   * 0x1f: Last written status offset. (GM45)
> + * 0x20-0x2f: Reserved (Gen6+)
>   *
> - * The area from dword 0x20 to 0x3ff is available for driver usage.
> + * The area from dword 0x30 to 0x3ff is available for driver usage.
>   */
> -#define I915_GEM_HWS_INDEX		0x20
> -#define I915_GEM_HWS_SCRATCH_INDEX	0x30
> +#define I915_GEM_HWS_INDEX		0x30
> +#define I915_GEM_HWS_SCRATCH_INDEX	0x40
>  #define I915_GEM_HWS_SCRATCH_ADDR (I915_GEM_HWS_SCRATCH_INDEX << MI_STORE_DWORD_INDEX_SHIFT)
>  
>  void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf);

Well, nothing much can go wnorg here!

Reviewed-by: Dave Gordon <david.s.gordon@intel.com>

But just FYI, these will all get changed again when we add support for
preemption (: because then we'll need more than one place to store
'sequence numbers' :)

.Dave.

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