[Intel-gfx] [PATCH] drm/i915/gt: Make the CTX_TIMESTAMP readable on !rcs

[Souza, Jose]

On Tue, 2020-06-02 at 16:48 +0100, Chris Wilson wrote:
> For reasons that be, the HW only allows usersace to read its own
> CTX_TIMESTAMP [context local HW runtime] on rcs. Make it available for
> all by adding it to the whitelists.
> 
> v2: The change took effect from Cometlake.
> v3: Ignore timestamps that autoincrement when validating the whitelist

I would have separated add the register to the whitelist from the selftest but anyways looks good.

Reviewed-by: José Roberto de Souza <jose.souza at intel.com>

> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gt/intel_workarounds.c   | 25 ++++++++++++++++++-
>  .../gpu/drm/i915/gt/selftest_workarounds.c    | 17 +++++++++++++
>  2 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> index 6e1accbcc045..0731bbcef06c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> @@ -1206,6 +1206,18 @@ static void cfl_whitelist_build(struct intel_engine_cs *engine)
>  			  RING_FORCE_TO_NONPRIV_RANGE_4);
>  }
>  
> +static void cml_whitelist_build(struct intel_engine_cs *engine)
> +{
> +	struct i915_wa_list *w = &engine->whitelist;
> +
> +	if (engine->class != RENDER_CLASS)
> +		whitelist_reg_ext(w,
> +				  RING_CTX_TIMESTAMP(engine->mmio_base),
> +				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
> +
> +	cfl_whitelist_build(engine);
> +}
> +
>  static void cnl_whitelist_build(struct intel_engine_cs *engine)
>  {
>  	struct i915_wa_list *w = &engine->whitelist;
> @@ -1256,9 +1268,15 @@ static void icl_whitelist_build(struct intel_engine_cs *engine)
>  		/* hucStatus2RegOffset */
>  		whitelist_reg_ext(w, _MMIO(0x23B0 + engine->mmio_base),
>  				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
> +		whitelist_reg_ext(w,
> +				  RING_CTX_TIMESTAMP(engine->mmio_base),
> +				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
>  		break;
>  
>  	default:
> +		whitelist_reg_ext(w,
> +				  RING_CTX_TIMESTAMP(engine->mmio_base),
> +				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
>  		break;
>  	}
>  }
> @@ -1290,6 +1308,9 @@ static void tgl_whitelist_build(struct intel_engine_cs *engine)
>  		whitelist_reg(w, HIZ_CHICKEN);
>  		break;
>  	default:
> +		whitelist_reg_ext(w,
> +				  RING_CTX_TIMESTAMP(engine->mmio_base),
> +				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
>  		break;
>  	}
>  }
> @@ -1307,7 +1328,9 @@ void intel_engine_init_whitelist(struct intel_engine_cs *engine)
>  		icl_whitelist_build(engine);
>  	else if (IS_CANNONLAKE(i915))
>  		cnl_whitelist_build(engine);
> -	else if (IS_COFFEELAKE(i915) || IS_COMETLAKE(i915))
> +	else if (IS_COMETLAKE(i915))
> +		cml_whitelist_build(engine);
> +	else if (IS_COFFEELAKE(i915))
>  		cfl_whitelist_build(engine);
>  	else if (IS_GEMINILAKE(i915))
>  		glk_whitelist_build(engine);
> diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> index 32785463ec9e..febc9e6692ba 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> @@ -417,6 +417,20 @@ static bool wo_register(struct intel_engine_cs *engine, u32 reg)
>  	return false;
>  }
>  
> +static bool timestamp(const struct intel_engine_cs *engine, u32 reg)
> +{
> +	reg = (reg - engine->mmio_base) & ~RING_FORCE_TO_NONPRIV_ACCESS_MASK;
> +	switch (reg) {
> +	case 0x358:
> +	case 0x35c:
> +	case 0x3a8:
> +		return true;
> +
> +	default:
> +		return false;
> +	}
> +}
> +
>  static bool ro_register(u32 reg)
>  {
>  	if ((reg & RING_FORCE_TO_NONPRIV_ACCESS_MASK) ==
> @@ -497,6 +511,9 @@ static int check_dirty_whitelist(struct intel_context *ce)
>  		if (wo_register(engine, reg))
>  			continue;
>  
> +		if (timestamp(engine, reg))
> +			continue; /* timestamps are expected to autoincrement */
> +
>  		ro_reg = ro_register(reg);
>  
>  		/* Clear non priv flags */