Re: [PATCH] drm/i915: Implement Dbuf overlap detection feature starting from LNL

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

On Mon, 28 Oct 2024, Vinod Govindapillai <vinod.govindapillai@intel.com> wrote:
> From: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
>
> From LNL onwards there is a new hardware feature, which
> allows to detect if the driver wrongly allocated DBuf
> entries and they happen to overlap. If enabled this will
> cause a specific interrupt to occur.
> We now handle it in the driver, by writing correspondent
> error message to kernel log.
>
> v2: Initialize dbuf overlap flag in runtime_defaults (Jani Nikula)
>
> v3: Unmask the overlap detection interrupt (Uma)
>
> Bspec: 69450
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display_device.c |  5 +++++
>  drivers/gpu/drm/i915/display/intel_display_device.h |  2 ++
>  drivers/gpu/drm/i915/display/intel_display_irq.c    | 10 ++++++++++
>  drivers/gpu/drm/i915/i915_reg.h                     |  2 ++
>  4 files changed, 19 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_device.c b/drivers/gpu/drm/i915/display/intel_display_device.c
> index aa22189e3853..0ac9a35e5f7b 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_device.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_device.c
> @@ -1227,6 +1227,7 @@ static const struct intel_display_device_info xe2_lpd_display = {
>  	.__runtime_defaults.fbc_mask =
>  		BIT(INTEL_FBC_A) | BIT(INTEL_FBC_B) |
>  		BIT(INTEL_FBC_C) | BIT(INTEL_FBC_D),
> +	.__runtime_defaults.has_dbuf_overlap_detection = true,
>  };
>  
>  static const struct intel_display_device_info xe2_hpd_display = {
> @@ -1668,6 +1669,10 @@ static void __intel_display_device_info_runtime_init(struct drm_i915_private *i9
>  		if (IS_DISPLAY_VER(i915, 10, 12) &&
>  		    (dfsm & GLK_DFSM_DISPLAY_DSC_DISABLE))
>  			display_runtime->has_dsc = 0;
> +
> +		if (DISPLAY_VER(i915) >= 20 &&

Always use display over i915 when possible:

DISPLAY_VER(display)

> +		    (dfsm & XE2LPD_DFSM_DBUF_OVERLAP_DISABLE))
> +			display_runtime->has_dbuf_overlap_detection = false;
>  	}
>  
>  	if (DISPLAY_VER(i915) >= 20) {
> diff --git a/drivers/gpu/drm/i915/display/intel_display_device.h b/drivers/gpu/drm/i915/display/intel_display_device.h
> index 071a36b51f79..6bf5672d874d 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_device.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_device.h
> @@ -125,6 +125,7 @@ enum intel_display_subplatform {
>  #define HAS_CDCLK_SQUASH(i915)		(DISPLAY_INFO(i915)->has_cdclk_squash)
>  #define HAS_CUR_FBC(i915)		(!HAS_GMCH(i915) && IS_DISPLAY_VER(i915, 7, 13))
>  #define HAS_D12_PLANE_MINIMIZATION(i915) (IS_ROCKETLAKE(i915) || IS_ALDERLAKE_S(i915))
> +#define HAS_DBUF_OVERLAP_DETECTION(__i915) (DISPLAY_RUNTIME_INFO(__i915)->has_dbuf_overlap_detection)
>  #define HAS_DDI(i915)			(DISPLAY_INFO(i915)->has_ddi)
>  #define HAS_DISPLAY(i915)		(DISPLAY_RUNTIME_INFO(i915)->pipe_mask != 0)
>  #define HAS_DMC(i915)			(DISPLAY_RUNTIME_INFO(i915)->has_dmc)
> @@ -232,6 +233,7 @@ struct intel_display_runtime_info {
>  	bool has_hdcp;
>  	bool has_dmc;
>  	bool has_dsc;
> +	bool has_dbuf_overlap_detection;
>  };
>  
>  struct intel_display_device_info {
> diff --git a/drivers/gpu/drm/i915/display/intel_display_irq.c b/drivers/gpu/drm/i915/display/intel_display_irq.c
> index a4f42ed3f21a..3d3c0c1fd184 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_irq.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_irq.c
> @@ -902,6 +902,13 @@ gen8_de_misc_irq_handler(struct drm_i915_private *dev_priv, u32 iir)
>  	struct intel_display *display = &dev_priv->display;
>  	bool found = false;
>  
> +	if (HAS_DBUF_OVERLAP_DETECTION(dev_priv)) {

HAS_DBUF_OVERLAP_DETECTION(display)

> +		if (iir & XE2LPD_DBUF_OVERLAP_DETECTED) {
> +			drm_warn(&dev_priv->drm,  "DBuf overlap detected\n");

drm_warn(display->drm, ...)

So the end result is that we get a warning, and that's it?

> +			found = true;
> +		}
> +	}
> +
>  	if (DISPLAY_VER(dev_priv) >= 14) {
>  		if (iir & (XELPDP_PMDEMAND_RSP |
>  			   XELPDP_PMDEMAND_RSPTOUT_ERR)) {
> @@ -1789,6 +1796,9 @@ void gen8_de_irq_postinstall(struct drm_i915_private *dev_priv)
>  			de_port_masked |= DSI0_TE | DSI1_TE;
>  	}
>  
> +	if (HAS_DBUF_OVERLAP_DETECTION(dev_priv))

HAS_DBUF_OVERLAP_DETECTION(display)

> +		de_misc_masked |= XE2LPD_DBUF_OVERLAP_DETECTED;
> +
>  	if (HAS_DSB(dev_priv))
>  		de_pipe_masked |= GEN12_DSB_INT(INTEL_DSB_0) |
>  			GEN12_DSB_INT(INTEL_DSB_1) |
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 405f409e9761..327d1aa3f211 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -2589,6 +2589,7 @@
>  #define  GEN8_DE_MISC_GSE		REG_BIT(27)
>  #define  GEN8_DE_EDP_PSR		REG_BIT(19)
>  #define  XELPDP_PMDEMAND_RSP		REG_BIT(3)
> +#define  XE2LPD_DBUF_OVERLAP_DETECTED	REG_BIT(1)
>  
>  #define GEN8_DE_MISC_IRQ_REGS		I915_IRQ_REGS(GEN8_DE_MISC_IMR, \
>  						      GEN8_DE_MISC_IER, \
> @@ -2894,6 +2895,7 @@
>  #define   SKL_DFSM_PIPE_C_DISABLE	(1 << 28)
>  #define   TGL_DFSM_PIPE_D_DISABLE	(1 << 22)
>  #define   GLK_DFSM_DISPLAY_DSC_DISABLE	(1 << 7)
> +#define   XE2LPD_DFSM_DBUF_OVERLAP_DISABLE	(1 << 3)
>  
>  #define XE2LPD_DE_CAP			_MMIO(0x41100)
>  #define   XE2LPD_DE_CAP_3DLUT_MASK	REG_GENMASK(31, 30)

-- 
Jani Nikula, Intel