Re: [PATCH v2] drm/i915/gen9: implement WaConextSwitchWithConcurrentTLBInvalidate

[Arun Siluvery <arun.siluvery@linux.intel.com>]

On 09/06/2016 20:19, tim.gore@intel.com wrote:
> From: Tim Gore <tim.gore@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.
>
> v2: move to gen9_init_workarounds (Arun)
>
> Signed-off-by: Tim Gore <tim.gore@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_reg.h         | 4 ++++
>   drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
>   2 files changed, 7 insertions(+)
>
> 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)
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index cf8d0bf..7c756ac 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1022,6 +1022,9 @@ static int gen9_init_workarounds(struct intel_engine_cs *engine)
>   	if (ret)
>   		return ret;
>
> +	/* WaConextSwitchWithConcurrentTLBInvalidate:skl,bxt,kbl */
> +	I915_WRITE(GEN9_CSFE_CHICKEN1_RCS, _MASKED_BIT_ENABLE(GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE));
> +
WA_SET_BIT_MASKED(GEN9_CSFE_CHICKEN1_RCS, 
GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE);

Please correct the spelling.
We should try to keep WA regs in some order although it is not true for 
some of the existing ones but we should try to follow this rule for the 
new ones; HW whitelist registers are normally kept at the end.
I think the correct place for this one is at the beginning of this 
function to maintain increasing order.

regards
Arun


>   	return 0;
>   }
>
>

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