[PATCH v2 7/9] drm/i915/pxp: MTL-KCR interrupt ctrl's are in GT-0

[Ceraolo Spurio, Daniele]

On 1/11/2023 1:42 PM, Alan Previn wrote:
> Despite KCR subsystem being in the media-tile (close to the
> GSC-CS), the IRQ controls for it are on GT-0 with other global
> IRQ controls. Thus, add a helper for KCR hw interrupt
> enable/disable functions to get the correct gt structure (for
> uncore) for MTL.
>
> In the helper, we get GT-0's handle for uncore when touching
> IRQ registers despite the pxp->ctrl_gt being the media-tile.
> No difference for legacy of course.
>
> Signed-off-by: Alan Previn <alan.previn.teres.alexis at intel.com>
> ---
>   drivers/gpu/drm/i915/pxp/intel_pxp_debugfs.c |  2 +-
>   drivers/gpu/drm/i915/pxp/intel_pxp_irq.c     | 23 +++++++++++++++++---
>   drivers/gpu/drm/i915/pxp/intel_pxp_irq.h     |  8 +++++++
>   3 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_debugfs.c b/drivers/gpu/drm/i915/pxp/intel_pxp_debugfs.c
> index 4b8e70caa3ad..9f6e300486b4 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp_debugfs.c
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp_debugfs.c
> @@ -44,7 +44,7 @@ static int pxp_terminate_get(void *data, u64 *val)
>   static int pxp_terminate_set(void *data, u64 val)
>   {
>   	struct intel_pxp *pxp = data;
> -	struct intel_gt *gt = pxp->ctrl_gt;
> +	struct intel_gt *gt = intel_pxp_get_irq_gt(pxp);

This doesn't seem to be required here. The only use of gt in this 
function is an assert below and both the root and media gt point to the 
same irq_lock, so it doesn't matter which one we're using. Should we 
keep it anyway just for safety in case things change in the future? or 
just add a comment instead?

>   
>   	if (!intel_pxp_is_active(pxp))
>   		return -ENODEV;
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c b/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c
> index 91e9622c07d0..2eef0c19e91a 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c
> @@ -8,6 +8,7 @@
>   #include "gt/intel_gt_regs.h"
>   #include "gt/intel_gt_types.h"
>   
> +#include "i915_drv.h"
>   #include "i915_irq.h"
>   #include "i915_reg.h"
>   
> @@ -17,6 +18,22 @@
>   #include "intel_pxp_types.h"
>   #include "intel_runtime_pm.h"
>   
> +/**
> + * intel_pxp_get_irq_gt - Find the correct GT that owns KCR interrupts
> + * @pxp: pointer to pxp struct
> + *
> + * For platforms with a single GT, we return the pxp->ctrl_gt (as expected)
> + * but for MTL+ that has a media-tile, although the KCR engine is in the
> + * media-tile (i.e. pxp->ctrl_gt), the IRQ controls are on the root tile.
> + */
> +struct intel_gt *intel_pxp_get_irq_gt(struct intel_pxp *pxp)
> +{
> +	if (pxp->uses_gsccs)
> +		return to_gt(pxp->ctrl_gt->i915);
> +
> +	return pxp->ctrl_gt;

AFAICT here we can skip the if and always return the root gt, because 
that's what happens in both cases. If you want to make sure we don't get 
issues in the future maybe instead add a:

GEM_BUG_ON(!i915->media_gt && !gt_is_root(pxp->ctrl_gt))

> +}
> +
>   /**
>    * intel_pxp_irq_handler - Handles PXP interrupts.
>    * @pxp: pointer to pxp struct
> @@ -29,7 +46,7 @@ void intel_pxp_irq_handler(struct intel_pxp *pxp, u16 iir)
>   	if (GEM_WARN_ON(!intel_pxp_is_enabled(pxp)))
>   		return;
>   
> -	gt = pxp->ctrl_gt;
> +	gt = intel_pxp_get_irq_gt(pxp);

Here also we only have the assert below

Daniele

>   
>   	lockdep_assert_held(gt->irq_lock);
>   
> @@ -68,7 +85,7 @@ static inline void pxp_irq_reset(struct intel_gt *gt)
>   
>   void intel_pxp_irq_enable(struct intel_pxp *pxp)
>   {
> -	struct intel_gt *gt = pxp->ctrl_gt;
> +	struct intel_gt *gt = intel_pxp_get_irq_gt(pxp);
>   
>   	spin_lock_irq(gt->irq_lock);
>   
> @@ -83,7 +100,7 @@ void intel_pxp_irq_enable(struct intel_pxp *pxp)
>   
>   void intel_pxp_irq_disable(struct intel_pxp *pxp)
>   {
> -	struct intel_gt *gt = pxp->ctrl_gt;
> +	struct intel_gt *gt = intel_pxp_get_irq_gt(pxp);
>   
>   	/*
>   	 * We always need to submit a global termination when we re-enable the
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_irq.h b/drivers/gpu/drm/i915/pxp/intel_pxp_irq.h
> index 8c292dc86f68..eea87c9eb62b 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp_irq.h
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp_irq.h
> @@ -9,6 +9,7 @@
>   #include <linux/types.h>
>   
>   struct intel_pxp;
> +struct intel_gt;
>   
>   #define GEN12_DISPLAY_PXP_STATE_TERMINATED_INTERRUPT BIT(1)
>   #define GEN12_DISPLAY_APP_TERMINATED_PER_FW_REQ_INTERRUPT BIT(2)
> @@ -23,6 +24,8 @@ struct intel_pxp;
>   void intel_pxp_irq_enable(struct intel_pxp *pxp);
>   void intel_pxp_irq_disable(struct intel_pxp *pxp);
>   void intel_pxp_irq_handler(struct intel_pxp *pxp, u16 iir);
> +struct intel_gt *intel_pxp_get_irq_gt(struct intel_pxp *pxp);
> +
>   #else
>   static inline void intel_pxp_irq_handler(struct intel_pxp *pxp, u16 iir)
>   {
> @@ -35,6 +38,11 @@ static inline void intel_pxp_irq_enable(struct intel_pxp *pxp)
>   static inline void intel_pxp_irq_disable(struct intel_pxp *pxp)
>   {
>   }
> +
> +static inline struct intel_gt *intel_pxp_get_irq_gt(struct intel_pxp *pxp)
> +{
> +	return NULL;
> +}
>   #endif
>   
>   #endif /* __INTEL_PXP_IRQ_H__ */