Re: [Intel-gfx] [PATCH] drm/i915/dg2: Don't try to process TBT interrupts

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Feb 11, 2022 at 11:19:03AM +0530, Ramalingam C wrote:
> From: Matt Roper <matthew.d.roper@intel.com>
> 
> DG2 is the first platform, that supports TC but not TBT.
> interrupt code is updated to avoid trying to process
> TBT-specific bits and registers.

Is that a real concern?

> 
> Cc: Swathi Dhanavanthri <swathi.dhanavanthri@intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h          |  1 +
>  drivers/gpu/drm/i915/i915_irq.c          | 12 ++++++++----
>  drivers/gpu/drm/i915/i915_pci.c          |  1 +
>  drivers/gpu/drm/i915/intel_device_info.h |  1 +
>  4 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 5b6fd792a8d7..b9294ff5a1e6 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1433,6 +1433,7 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
>  #define HAS_PSR(dev_priv)		 (INTEL_INFO(dev_priv)->display.has_psr)
>  #define HAS_PSR_HW_TRACKING(dev_priv) \
>  	(INTEL_INFO(dev_priv)->display.has_psr_hw_tracking)
> +#define HAS_TC_WITHOUT_TBT(dev_priv)	 (INTEL_INFO(dev_priv)->display.has_tc_without_tbt)
>  #define HAS_PSR2_SEL_FETCH(dev_priv)	 (DISPLAY_VER(dev_priv) >= 12)
>  #define HAS_TRANSCODER(dev_priv, trans)	 ((INTEL_INFO(dev_priv)->display.cpu_transcoder_mask & BIT(trans)) != 0)
>  
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index fdd568ba4a16..72b9888b2acf 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -2245,7 +2245,8 @@ static void gen11_hpd_irq_handler(struct drm_i915_private *dev_priv, u32 iir)
>  {
>  	u32 pin_mask = 0, long_mask = 0;
>  	u32 trigger_tc = iir & GEN11_DE_TC_HOTPLUG_MASK;
> -	u32 trigger_tbt = iir & GEN11_DE_TBT_HOTPLUG_MASK;
> +	u32 trigger_tbt = HAS_TC_WITHOUT_TBT(dev_priv) ? 0 :
> +		iir & GEN11_DE_TBT_HOTPLUG_MASK;
>  
>  	if (trigger_tc) {
>  		u32 dig_hotplug_reg;
> @@ -3468,7 +3469,8 @@ static void gen11_hpd_irq_setup(struct drm_i915_private *dev_priv)
>  	intel_uncore_posting_read(&dev_priv->uncore, GEN11_DE_HPD_IMR);

Just above here is where the problem happens because it will
unmask all the TBT irqs. I'm thinking we might want to
split hpd_gen11[] into tc vs. tbt variants and introduce
i915->hotplug.hpd_tbt[].

>  
>  	gen11_tc_hpd_detection_setup(dev_priv);
> -	gen11_tbt_hpd_detection_setup(dev_priv);
> +	if (!HAS_TC_WITHOUT_TBT(dev_priv))
> +		gen11_tbt_hpd_detection_setup(dev_priv);

Does the GEN11_TBT_HOTPLUG_CTL register still exist though? 
If yes, then we probably want to keep initializing it, just
making sure to turn off the relevant bits.

>  
>  	if (INTEL_PCH_TYPE(dev_priv) >= PCH_ICP)
>  		icp_hpd_irq_setup(dev_priv);
> @@ -3828,8 +3830,10 @@ static void gen8_de_irq_postinstall(struct drm_i915_private *dev_priv)
>  
>  	if (DISPLAY_VER(dev_priv) >= 11) {
>  		u32 de_hpd_masked = 0;
> -		u32 de_hpd_enables = GEN11_DE_TC_HOTPLUG_MASK |
> -				     GEN11_DE_TBT_HOTPLUG_MASK;
> +		u32 de_hpd_enables = GEN11_DE_TC_HOTPLUG_MASK;
> +
> +		if (!HAS_TC_WITHOUT_TBT(dev_priv))
> +			de_hpd_enables |= GEN11_DE_TBT_HOTPLUG_MASK;
>  
>  		GEN3_IRQ_INIT(uncore, GEN11_DE_HPD_, ~de_hpd_masked,
>  			      de_hpd_enables);

This code seems fine as is. It just sets all the enable bits
but leaves everything masked. Exactly as everything else is
handled (minus the odd SDEIER expection).

> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> index 467252f885c2..1ad5593e925f 100644
> --- a/drivers/gpu/drm/i915/i915_pci.c
> +++ b/drivers/gpu/drm/i915/i915_pci.c
> @@ -1046,6 +1046,7 @@ static const struct intel_device_info dg2_info = {
>  	.graphics.rel = 55,
>  	.media.rel = 55,
>  	PLATFORM(INTEL_DG2),
> +	.display.has_tc_without_tbt = 1,
>  	.has_guc_deprivilege = 1,
>  	.has_64k_pages = 1,
>  	.platform_engine_mask =
> diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.h
> index 27dcfe6f2429..4d8cfd41aa31 100644
> --- a/drivers/gpu/drm/i915/intel_device_info.h
> +++ b/drivers/gpu/drm/i915/intel_device_info.h
> @@ -171,6 +171,7 @@ enum intel_ppgtt_type {
>  	func(has_overlay); \
>  	func(has_psr); \
>  	func(has_psr_hw_tracking); \
> +	func(has_tc_without_tbt); \
>  	func(overlay_needs_physical); \
>  	func(supports_tv);
>  
> -- 
> 2.20.1

-- 
Ville Syrjälä
Intel