Re: [PATCH v6 13/20] drm/i915/guc: Provide register list to be saved/restored during engine reset

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On ke, 2017-04-19 at 11:35 -0700, Michel Thierry wrote:
> From: Arun Siluvery <arun.siluvery@linux.intel.com>
> 
> GuC expects a list of registers from the driver which are saved/restored
> during engine reset. The type of value to be saved is controlled by
> flags. We provide a minimal set of registers that we want GuC to save and
> restore. This is not an issue in case of engine reset as driver initializes
> most of them following an engine reset, but in case of media reset (aka
> watchdog reset) which is completely internal to GuC (including resubmission
> of hung workload), it is necessary to provide this list, otherwise GuC won't
> be able to schedule further workloads after a reset. This is the minimal
> set of registers identified for things to work as expected but if we see
> any new issues, this register list can be expanded.
> 
> In order to not loose any existing workarounds, we have to let GuC know
> the registers and its values. These will be reapplied after the reset.
> Note that we can't just read the current value because most of these
> registers are masked (so we have a workaround for a workaround for a
> workaround).
> 
> v2: REGSET_MASKED is too difficult for GuC, use REGSET_SAVE_DEFAULT_VALUE
> and current value from RING_MODE reg instead; no need to preserve
> head/tail either, be extra paranoid and save whitelisted registers (Daniele).
> 
> v3: Workarounds added only once during _init_workarounds also have to
> been restored, or we risk loosing them after internal GuC reset
> (Daniele).
> 
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
> Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
> Signed-off-by: Michel Thierry <michel.thierry@intel.com>

<SNIP>

> @@ -732,15 +755,16 @@ static int gen9_init_workarounds(struct intel_engine_cs *engine)
> >  	int ret;
>  
>  	/* WaConextSwitchWithConcurrentTLBInvalidate:skl,bxt,kbl,glk */
> -	I915_WRITE(GEN9_CSFE_CHICKEN1_RCS, _MASKED_BIT_ENABLE(GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE));
> +	I915_GUC_REG_WRITE(GEN9_CSFE_CHICKEN1_RCS,
> +			   _MASKED_BIT_ENABLE(GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE));

To make grepping easier, how about?

	I915_WRITE(GUC_REG(GEN9_CSFE_CHICKEN1_RCS),
		   ...);

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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