Re: [PATCH 1/2] drm/i915: Switch to fake context on older gens

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 14 Mar 2014, Mika Kuoppala <mika.kuoppala@linux.intel.com> wrote:
> We used to have per file descriptor hang stats for the
> i915_get_reset_stats_ioctl() and for default context banning.
>
> commit 0eea67eb26000657079b7fc41079097942339452
> Author: Ben Widawsky <ben@bwidawsk.net>
> Date:   Fri Dec 6 14:11:19 2013 -0800
>
>     drm/i915: Create a per file_priv default context
>
> made having separate hangstats in file_private redundant
> as i915_hw_context already contained hangstats. So
>
> commit c482972a086e03e6a6d27e4f7af2d868bf659648
> Author: Ben Widawsky <benjamin.widawsky@intel.com>
> Date:   Fri Dec 6 14:11:20 2013 -0800
>
>     drm/i915: Piggy back hangstats off of contexts
>
> consolidated the hangstats and enabled further improvements.
>
> commit 44e2c0705a19e09d7b0f30a591f92e473e5ef89e
> Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Date:   Thu Jan 30 16:01:15 2014 +0200
>
>     drm/i915: Use i915_hw_context to set reset stats
>
> tried to reap full benefits of consolidation but fell short
> as we never 'switch' to the fake private context on gens
> that don't have hw_contexts, so request->ctx remained NULL
> on those.
>
> Fix this by 'switching' to fake context so that when
> request is submitted to ring, proper context gets assigned
> to it.
>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=76055

I'd say this still applies:

Tested-by: Lu Hua <huax.lu@intel.com>

> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_context.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index ce41cff..b5a5837 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -775,9 +775,11 @@ int i915_switch_context(struct intel_ring_buffer *ring,
>  
>  	BUG_ON(file && to == NULL);
>  
> -	/* We have the fake context, but don't supports switching. */
> -	if (!HAS_HW_CONTEXTS(ring->dev))
> +	/* We have the fake context */
> +	if (!HAS_HW_CONTEXTS(ring->dev)) {
> +		ring->last_context = to;
>  		return 0;
> +	}
>  
>  	return do_switch(ring, to);
>  }
> -- 
> 1.7.9.5
>
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-- 
Jani Nikula, Intel Open Source Technology Center