Re: [PATCH 1/6] drm/i915/gt: Ignore TLB invalidations on idle engines

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 15/06/2022 16:27, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@xxxxxxxxx>
>
> As an extension of the current skip TLB invalidations,
> check if the device is powered down prior to any engine activity,
>
> as, on such cases, all the TLBs were already invalidated, so an
> explicit TLB invalidation is not needed.
>
> This becomes more significant  with GuC, as it can only do so when
> the connection to the GuC is awake.
>
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Hmmm is this a fix or "an extension" as the commit text mentions both 
options?! GuC angle does not appear relevant for upstream yet so is cc: 
stable really required is the question.

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris.p.wilson@xxxxxxxxx>
> Cc: Fei Yang <fei.yang@xxxxxxxxx>
> Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Acked-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> ---
>
> See [PATCH 0/6] at: https://lore.kernel.org/all/cover.1655306128.git.mchehab@xxxxxxxxxx/
>
>   drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 +++++----
>   drivers/gpu/drm/i915/gt/intel_gt.c        | 26 +++++++++++++++++------
>   drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 +++
>   3 files changed, 28 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 97c820eee115..6835279943df 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -6,14 +6,15 @@
>   
>   #include <drm/drm_cache.h>
>   
> +#include "gt/intel_gt.h"
> +#include "gt/intel_gt_pm.h"
> +
>   #include "i915_drv.h"
>   #include "i915_gem_object.h"
>   #include "i915_scatterlist.h"
>   #include "i915_gem_lmem.h"
>   #include "i915_gem_mman.h"
>   
> -#include "gt/intel_gt.h"
> -
>   void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
>   				 struct sg_table *pages,
>   				 unsigned int sg_page_sizes)
> @@ -217,10 +218,11 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>   
>   	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
>   		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +		struct intel_gt *gt = to_gt(i915);
>   		intel_wakeref_t wakeref;
>   
> -		with_intel_runtime_pm_if_active(&i915->runtime_pm, wakeref)
> -			intel_gt_invalidate_tlbs(to_gt(i915));
> +		with_intel_gt_pm_if_awake(gt, wakeref)
> +			intel_gt_invalidate_tlbs(gt);
>   	}
>   
>   	return pages;
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index f33290358c51..d5ed6a6ac67c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -11,6 +11,7 @@
>   
>   #include "i915_drv.h"
>   #include "intel_context.h"
> +#include "intel_engine_pm.h"
>   #include "intel_engine_regs.h"
>   #include "intel_gt.h"
>   #include "intel_gt_buffer_pool.h"
> @@ -1216,6 +1217,7 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	struct drm_i915_private *i915 = gt->i915;
>   	struct intel_uncore *uncore = gt->uncore;
>   	struct intel_engine_cs *engine;
> +	intel_engine_mask_t awake, tmp;
>   	enum intel_engine_id id;
>   	const i915_reg_t *regs;
>   	unsigned int num = 0;
> @@ -1239,12 +1241,27 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   
>   	GEM_TRACE("\n");
>   
> -	assert_rpm_wakelock_held(&i915->runtime_pm);
> -
>   	mutex_lock(&gt->tlb_invalidate_lock);
>   	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>   
> +	awake = 0;
>   	for_each_engine(engine, gt, id) {
> +		struct reg_and_bit rb;
> +
> +		if (!intel_engine_pm_is_awake(engine))
> +			continue;
> +
> +		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> +		if (!i915_mmio_reg_offset(rb.reg))
> +			continue;
> +
> +		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
> +		awake |= engine->mask;
> +	}
> +
> +	for_each_engine_masked(engine, gt, awake, tmp) {
> +		struct reg_and_bit rb;
> +
>   		/*
>   		 * HW architecture suggest typical invalidation time at 40us,
>   		 * with pessimistic cases up to 100us and a recommendation to
> @@ -1252,13 +1269,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   		 */
>   		const unsigned int timeout_us = 100;
>   		const unsigned int timeout_ms = 4;
> -		struct reg_and_bit rb;
>   
>   		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> -		if (!i915_mmio_reg_offset(rb.reg))
> -			continue;
> -
> -		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
>   		if (__intel_wait_for_register_fw(uncore,
>   						 rb.reg, rb.bit, 0,
>   						 timeout_us, timeout_ms,
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> index bc898df7a48c..a334787a4939 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> @@ -55,6 +55,9 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
>   	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
>   	     intel_gt_pm_put(gt), tmp = 0)
>   
> +#define with_intel_gt_pm_if_awake(gt, wf) \
> +	for (wf = intel_gt_pm_get_if_awake(gt); wf; intel_gt_pm_put_async(gt), wf = 0)
> +
>   static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
>   {
>   	return intel_wakeref_wait_for_idle(&gt->wakeref);