Re: [PATCH 3/5] drm/i915: Extract CSB status read

[Michel Thierry <michel.thierry@intel.com>]

On 1/5/2016 6:30 PM, Ben Widawsky wrote:
> This is a useful thing to have around as a function because the mechanism may
> change in the future.
>
> There is a net increase in LOC here, and it will continue to be the case on GEN8
> and GEN9 - but future GENs may have an alternate mechanism for doing this.
>
> Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
> ---
>   drivers/gpu/drm/i915/intel_lrc.c | 19 ++++++++++++++++---
>   1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 14affaa..23839ff 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -496,6 +496,19 @@ static bool execlists_check_remove_request(struct intel_engine_cs *ring,
>          return false;
>   }
>
> +static void get_context_status(struct intel_engine_cs *ring,
> +                              u8 read_pointer,
> +                              u32 *status, u32 *context_id)
> +{
> +       struct drm_i915_private *dev_priv = ring->dev->dev_private;
> +
> +       if (WARN_ON(read_pointer >= GEN8_CSB_ENTRIES))
> +               return;
> +
> +       *status = I915_READ(RING_CONTEXT_STATUS_BUF_LO(ring, read_pointer));
> +       *context_id = I915_READ(RING_CONTEXT_STATUS_BUF_HI(ring, read_pointer));
> +}
> +
>   /**
>    * intel_lrc_irq_handler() - handle Context Switch interrupts
>    * @ring: Engine Command Streamer to handle.
> @@ -523,9 +536,9 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
>          spin_lock(&ring->execlist_lock);
>
>          while (read_pointer < write_pointer) {
> -               read_pointer++;
> -               status = I915_READ(RING_CONTEXT_STATUS_BUF_LO(ring, read_pointer % GEN8_CSB_ENTRIES));
> -               status_id = I915_READ(RING_CONTEXT_STATUS_BUF_HI(ring, read_pointer % GEN8_CSB_ENTRIES));
> +
> +               get_context_status(ring, ++read_pointer % GEN8_CSB_ENTRIES,
> +                                  &status, &status_id);
>
>                  if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
>                          continue;
> --
> 2.6.4

Future GENs may need a completely new lrc_irq_handler anyway.

Reviewed-by: Michel Thierry <michel.thierry@intel.com>

>
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