[Intel-gfx] [PATCH] drm/i915/gen9: implement WaConextSwitchWithConcurrentTLBInvalidate

[Arun Siluvery]

On 09/06/2016 13:48, tim.gore at intel.com wrote:
> From: Tim Gore <tim.gore at intel.com>
>
> This patch enables a workaround for a mid thread preemption
> issue where a hardware timing problem can prevent the
> context restore from happening, leading to a hang.
>
> Signed-off-by: Tim Gore <tim.gore at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem_gtt.c | 6 ++++++
>   drivers/gpu/drm/i915/i915_reg.h     | 4 ++++
>   2 files changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 4668477..e9046f6 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -2156,6 +2156,12 @@ static void gtt_write_workarounds(struct drm_device *dev)
>   		I915_WRITE(GEN8_L3_LRA_1_GPGPU, GEN9_L3_LRA_1_GPGPU_DEFAULT_VALUE_SKL);
>   	else if (IS_BROXTON(dev))
>   		I915_WRITE(GEN8_L3_LRA_1_GPGPU, GEN9_L3_LRA_1_GPGPU_DEFAULT_VALUE_BXT);
> +
> +	/* WaConextSwitchWithConcurrentTLBInvalidate:gen9 */
> +	if (IS_GEN9(dev))
> +	{
> +		I915_WRITE(GEN9_CSFE_CHICKEN1_RCS, _MASKED_BIT_ENABLE(GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE));
> +	}
This is not the correct place, it should be added in 
gen9_init_workarounds() in intel_ringbuffer.c as it applies to both skl 
and bxt.

Please also correct the spelling and we usually mention both skl, bxt 
instead of gen9.
WaContextSwitchWithConcurrentTLBInvalidate:skl,bxt

regards
Arun

>   }
>
>   static int i915_ppgtt_init(struct drm_device *dev, struct i915_hw_ppgtt *ppgtt)
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 81d1896..2a6fc62 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1810,6 +1810,10 @@ enum skl_disp_power_wells {
>   #define   GEN9_IZ_HASHING_MASK(slice)			(0x3 << ((slice) * 2))
>   #define   GEN9_IZ_HASHING(slice, val)			((val) << ((slice) * 2))
>
> +/* chicken reg for WaConextSwitchWithConcurrentTLBInvalidate */
> +#define GEN9_CSFE_CHICKEN1_RCS _MMIO(0x20D4)
> +#define   GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE (1 << 2)
> +
>   /* WaClearTdlStateAckDirtyBits */
>   #define GEN8_STATE_ACK		_MMIO(0x20F0)
>   #define GEN9_STATE_ACK_SLICE1	_MMIO(0x20F8)
>