Re: [Intel-gfx] [PATCH v2 7/8] drm/i915: Introduce a non-blocking power domain for vblank interrupts

On Tue, 2017-12-19 at 13:41 -0800, Rodrigo Vivi wrote:

On Tue, Dec 19, 2017 at 05:26:58AM +0000, Dhinakaran Pandiyan wrote:

...

When DC states are enabled and PSR is active, the hardware enters DC5/DC6 states resulting in frame counter resets. The frame counter resets mess up the vblank counting logic. In order to disable DC states when vblank interrupts are required and to disallow DC states when vblanks interrupts are already enabled, introduce a new VBLANK power domain. Since this power domain reference needs to be acquired and released in atomic context, _vblank_get() and _vblank_put() methods skip the power_domain mutex.

v2: Fix deadlock by switching irqsave spinlock. Implement atomic version of get_if_enabled. Modify power_domain_verify_state to check power well use count and enabled status atomically. Rewrite of intel_power_well_{get,put}

Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Rodrigo Vivi rodrigo.vivi@intel.com

• Cc: Imre Deak imre.deak@intel.com

...

Signed-off-by: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com

drivers/gpu/drm/i915/i915_drv.h | 18 ++++ drivers/gpu/drm/i915/intel_drv.h | 3 + drivers/gpu/drm/i915/intel_runtime_pm.c | 184 +++++++++++++++++++++++++++++--- 3 files changed, 192 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index ddadeb9eaf49..db597c5ebaed 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -397,6 +397,7 @@ enum intel_display_power_domain { POWER_DOMAIN_AUX_C, POWER_DOMAIN_AUX_D, POWER_DOMAIN_GMBUS,

• POWER_DOMAIN_VBLANK, POWER_DOMAIN_MODESET, POWER_DOMAIN_GT_IRQ, POWER_DOMAIN_INIT,

@@ -1476,6 +1477,23 @@ struct i915_power_well { bool has_fuses:1; } hsw; };

• /* Lock to serialize access to count, hw_enabled and ops, used for

• * power wells that have supports_atomix_ctx set to True.
  

• */
  

• spinlock_t lock;
• /* Indicates that the get/put methods for this power well can be called

• * in atomic contexts, requires .ops to not sleep. This is valid
  

• * only for the DC_OFF power well currently.
  

• */
  

• bool supports_atomic_ctx;
• /* DC_OFF power well was disabled since the last time vblanks were

• * disabled.
  

• */
  

• bool dc_off_disabled;
• const struct i915_power_well_ops *ops;

};

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 48676e99316e..6822118f3c4d 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -1798,6 +1798,9 @@ bool intel_display_power_get_if_enabled(struct drm_i915_private *dev_priv, enum intel_display_power_domain domain); void intel_display_power_put(struct drm_i915_private *dev_priv, enum intel_display_power_domain domain); +void intel_display_power_vblank_get(struct drm_i915_private *dev_priv,

• 		    bool *needs_restore);
  

+void intel_display_power_vblank_put(struct drm_i915_private *dev_priv);

static inline void assert_rpm_device_not_suspended(struct drm_i915_private *dev_priv) diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c index 992caec1fbc4..fc6812ed6137 100644 --- a/drivers/gpu/drm/i915/intel_runtime_pm.c +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c @@ -56,6 +56,19 @@ static struct i915_power_well * lookup_power_well(struct drm_i915_private *dev_priv, enum i915_power_well_id power_well_id);

+/* Optimize for the case when this is called from atomic contexts,

• • although the case is unlikely.
• */

+#define power_well_lock(power_well, flags) do { \

• if (likely(power_well->supports_atomic_ctx)) \

you mention unlikely on commend and call likely here, why?

It is unlikely that the power well is going to be DC_OFF, but we need to optimize for that case as it can be called from atomic contexts.

...

• spin_lock_irqsave(&power_well->lock, flags);	\
  

• } while (0)

+#define power_well_unlock(power_well, flags) do { \

• if (likely(power_well->supports_atomic_ctx)) \

• spin_unlock_irqrestore(&power_well->lock, flags);	\
  

• } while (0)

const char * intel_display_power_domain_str(enum intel_display_power_domain domain) { @@ -126,6 +139,8 @@ intel_display_power_domain_str(enum intel_display_power_domain domain) return "AUX_D"; case POWER_DOMAIN_GMBUS: return "GMBUS";

• case POWER_DOMAIN_VBLANK:

• return "VBLANK";
  

  case POWER_DOMAIN_INIT: return "INIT"; case POWER_DOMAIN_MODESET:

@@ -141,6 +156,9 @@ intel_display_power_domain_str(enum intel_display_power_domain domain) static void intel_power_well_enable(struct drm_i915_private *dev_priv, struct i915_power_well *power_well) {

• if (power_well->supports_atomic_ctx)

why not (un)likely check here as well?

...

• assert_spin_locked(&power_well->lock);
  

• DRM_DEBUG_KMS("enabling %s\n", power_well->name); power_well->ops->enable(dev_priv, power_well); power_well->hw_enabled = true;

@@ -149,26 +167,43 @@ static void intel_power_well_enable(struct drm_i915_private *dev_priv, static void intel_power_well_disable(struct drm_i915_private *dev_priv, struct i915_power_well *power_well) {

• if (power_well->supports_atomic_ctx)

• assert_spin_locked(&power_well->lock);
  

• DRM_DEBUG_KMS("disabling %s\n", power_well->name); power_well->hw_enabled = false; power_well->ops->disable(dev_priv, power_well);

}

-static void intel_power_well_get(struct drm_i915_private *dev_priv, +static void __intel_power_well_get(struct drm_i915_private *dev_priv, struct i915_power_well *power_well) { if (!power_well->count++) intel_power_well_enable(dev_priv, power_well); }

+static void intel_power_well_get(struct drm_i915_private *dev_priv,

• 		 struct i915_power_well *power_well)
  

+{

• unsigned long flags = 0;
• power_well_lock(power_well, flags);
• __intel_power_well_get(dev_priv, power_well);
• power_well_unlock(power_well, flags);

+}

static void intel_power_well_put(struct drm_i915_private *dev_priv, struct i915_power_well *power_well) {

• unsigned long flags = 0;

• power_well_lock(power_well, flags); WARN(!power_well->count, "Use count on power well %s is already zero", power_well->name);

  if (!--power_well->count) intel_power_well_disable(dev_priv, power_well);

• power_well_unlock(power_well, flags);

}

/** @@ -726,6 +761,7 @@ static void gen9_dc_off_power_well_disable(struct drm_i915_private *dev_priv, skl_enable_dc6(dev_priv); else if (dev_priv->csr.allowed_dc_mask & DC_STATE_EN_UPTO_DC5) gen9_enable_dc5(dev_priv);

• power_well->dc_off_disabled = true;

why do we need to track this like this?

Seems a big deviation of the hole generic power well state...

If the power well was turned off much later than disable_vblank, the following enable_vblank call has no idea whether it has to compute the missed vblanks.

1) put vblank ref -> put AUX A ref -> get vblank ref dc_off is turned off after we put AUX_A ref, needs computing missed vblanks.

2) get AUX A ref -> put vblank ref -> get_vblank ref dc_off is never turned off, no need to compute missed vblanks.

...

}

static void i9xx_power_well_sync_hw_noop(struct drm_i915_private *dev_priv, @@ -1443,6 +1479,58 @@ static void chv_pipe_power_well_disable(struct drm_i915_private *dev_priv, chv_set_pipe_power_well(dev_priv, power_well, false); }

+void intel_display_power_vblank_get(struct drm_i915_private *dev_priv,

• 		    bool *needs_restore)
  

+{

• struct i915_power_domains *power_domains = &dev_priv->power_domains;
• struct i915_power_well *power_well;
• enum intel_display_power_domain domain = POWER_DOMAIN_VBLANK;
• *needs_restore = false;
• if (!HAS_CSR(dev_priv))

• return;
  

• if (!CAN_PSR(dev_priv))

• return;
  

• intel_runtime_pm_get_noresume(dev_priv);
• for_each_power_domain_well(dev_priv, power_well, BIT_ULL(domain)) {

• unsigned long flags = 0;
  

• power_well_lock(power_well, flags);
  

• __intel_power_well_get(dev_priv, power_well);
  

• *needs_restore = power_well->dc_off_disabled;
  

• power_well->dc_off_disabled = false;
  

• power_well_unlock(power_well, flags);
  

• }
• atomic_inc(&power_domains->domain_use_count[domain]);

+}

+void intel_display_power_vblank_put(struct drm_i915_private *dev_priv) +{

• struct i915_power_domains *power_domains = &dev_priv->power_domains;
• struct i915_power_well *power_well;
• enum intel_display_power_domain domain = POWER_DOMAIN_VBLANK;
• if (!HAS_CSR(dev_priv))

• return;
  

• if (!CAN_PSR(dev_priv))

• return;
  

• WARN(atomic_dec_return(&power_domains->domain_use_count[domain]) < 0,

•     "Use count on domain %s was already zero\n",
  

•     intel_display_power_domain_str(domain));
  

• for_each_power_domain_well_rev(dev_priv, power_well, BIT_ULL(domain))

• intel_power_well_put(dev_priv, power_well);
  

• intel_runtime_pm_put(dev_priv);

+}

static void __intel_display_power_get_domain(struct drm_i915_private *dev_priv, enum intel_display_power_domain domain) @@ -1482,6 +1570,38 @@ void intel_display_power_get(struct drm_i915_private *dev_priv, mutex_unlock(&power_domains->lock); }

+static bool dc_off_get_if_enabled(struct drm_i915_private *dev_priv,

• 		  enum intel_display_power_domain domain)
  

+{

• struct i915_power_well *power_well;
• bool is_enabled;
• unsigned long flags = 0;
• power_well = lookup_power_well(dev_priv, SKL_DISP_PW_DC_OFF);
• if (!power_well || !(power_well->domains & domain))

• return true;
  

• power_well_lock(power_well, flags);
• is_enabled = power_well->hw_enabled;
• if (is_enabled)

• __intel_power_well_get(dev_priv, power_well);
  

• power_well_unlock(power_well, flags);
• return is_enabled;

+}

+static void dc_off_put(struct drm_i915_private *dev_priv,

•        enum intel_display_power_domain domain)
  

+{

• struct i915_power_well *power_well;
• power_well = lookup_power_well(dev_priv, SKL_DISP_PW_DC_OFF);
• if (!power_well || !(power_well->domains & domain))

• return;
  

• intel_power_well_put(dev_priv, power_well);

+}

/**

• intel_display_power_get_if_enabled - grab a reference for an enabled display power domain
• @dev_priv: i915 device instance

@@ -1498,20 +1618,24 @@ bool intel_display_power_get_if_enabled(struct drm_i915_private *dev_priv, enum intel_display_power_domain domain) { struct i915_power_domains *power_domains = &dev_priv->power_domains;

• bool is_enabled;

• bool is_enabled = false;

  if (!intel_runtime_pm_get_if_in_use(dev_priv)) return false;

  mutex_lock(&power_domains->lock);

• if (!dc_off_get_if_enabled(dev_priv, domain))

• goto out;
  

• if (__intel_display_power_is_enabled(dev_priv, domain)) { __intel_display_power_get_domain(dev_priv, domain); is_enabled = true;

• } else {

• is_enabled = false;
  

  }

• dc_off_put(dev_priv, domain);

+out: mutex_unlock(&power_domains->lock);

if (!is_enabled) @@ -1709,6 +1833,7 @@ void intel_display_power_put(struct drm_i915_private *dev_priv, BIT_ULL(POWER_DOMAIN_GT_IRQ) | \ BIT_ULL(POWER_DOMAIN_MODESET) | \ BIT_ULL(POWER_DOMAIN_AUX_A) | \

• BIT_ULL(POWER_DOMAIN_VBLANK) | \ BIT_ULL(POWER_DOMAIN_INIT))

#define BXT_DISPLAY_POWERWELL_2_POWER_DOMAINS ( \ @@ -1732,6 +1857,7 @@ void intel_display_power_put(struct drm_i915_private *dev_priv, BIT_ULL(POWER_DOMAIN_GT_IRQ) | \ BIT_ULL(POWER_DOMAIN_MODESET) | \ BIT_ULL(POWER_DOMAIN_AUX_A) | \

• BIT_ULL(POWER_DOMAIN_VBLANK) | \ BIT_ULL(POWER_DOMAIN_INIT))

#define BXT_DPIO_CMN_A_POWER_DOMAINS ( \ BIT_ULL(POWER_DOMAIN_PORT_DDI_A_LANES) | \ @@ -1791,6 +1917,7 @@ void intel_display_power_put(struct drm_i915_private *dev_priv, BIT_ULL(POWER_DOMAIN_GT_IRQ) | \ BIT_ULL(POWER_DOMAIN_MODESET) | \ BIT_ULL(POWER_DOMAIN_AUX_A) | \

• BIT_ULL(POWER_DOMAIN_VBLANK) | \ BIT_ULL(POWER_DOMAIN_INIT))

#define CNL_DISPLAY_POWERWELL_2_POWER_DOMAINS ( \ @@ -1838,6 +1965,7 @@ void intel_display_power_put(struct drm_i915_private *dev_priv, CNL_DISPLAY_POWERWELL_2_POWER_DOMAINS | \ BIT_ULL(POWER_DOMAIN_MODESET) | \ BIT_ULL(POWER_DOMAIN_AUX_A) | \

• BIT_ULL(POWER_DOMAIN_VBLANK) | \ BIT_ULL(POWER_DOMAIN_INIT))

static const struct i915_power_well_ops i9xx_always_on_power_well_ops = { @@ -2071,9 +2199,12 @@ bool intel_display_power_well_is_enabled(struct drm_i915_private *dev_priv, { struct i915_power_well *power_well; bool ret;

• unsigned long flags = 0;

  power_well = lookup_power_well(dev_priv, power_well_id);

• power_well_lock(power_well, flags); ret = power_well->ops->is_enabled(dev_priv, power_well);

• power_well_unlock(power_well, flags);

  return ret;

} @@ -2108,6 +2239,8 @@ static struct i915_power_well skl_power_wells[] = { .domains = SKL_DISPLAY_DC_OFF_POWER_DOMAINS, .ops = &gen9_dc_off_power_well_ops, .id = SKL_DISP_PW_DC_OFF,

• .supports_atomic_ctx = true,
  

• .dc_off_disabled = false,
  

  }, { .name = "power well 2",

@@ -2168,6 +2301,8 @@ static struct i915_power_well bxt_power_wells[] = { .domains = BXT_DISPLAY_DC_OFF_POWER_DOMAINS, .ops = &gen9_dc_off_power_well_ops, .id = SKL_DISP_PW_DC_OFF,

• .supports_atomic_ctx = true,
  

• .dc_off_disabled = false,
  

  }, { .name = "power well 2",

@@ -2223,6 +2358,8 @@ static struct i915_power_well glk_power_wells[] = { .domains = GLK_DISPLAY_DC_OFF_POWER_DOMAINS, .ops = &gen9_dc_off_power_well_ops, .id = SKL_DISP_PW_DC_OFF,

• .supports_atomic_ctx = true,
  

• .dc_off_disabled = false,
  

  }, { .name = "power well 2",

@@ -2347,6 +2484,8 @@ static struct i915_power_well cnl_power_wells[] = { .domains = CNL_DISPLAY_DC_OFF_POWER_DOMAINS, .ops = &gen9_dc_off_power_well_ops, .id = SKL_DISP_PW_DC_OFF,

• .supports_atomic_ctx = true,
  

• .dc_off_disabled = false,
  

  }, { .name = "power well 2",

@@ -2475,6 +2614,7 @@ static void assert_power_well_ids_unique(struct drm_i915_private *dev_priv) int intel_power_domains_init(struct drm_i915_private *dev_priv) { struct i915_power_domains *power_domains = &dev_priv->power_domains;

• struct i915_power_well *power_well;

  i915_modparams.disable_power_well = sanitize_disable_power_well_option(dev_priv,

@@ -2512,6 +2652,10 @@ int intel_power_domains_init(struct drm_i915_private *dev_priv) set_power_wells(power_domains, i9xx_always_on_power_well); }

• for_each_power_well(dev_priv, power_well)

• if (power_well->supports_atomic_ctx)
  

• 	spin_lock_init(&power_well->lock);
  

• assert_power_well_ids_unique(dev_priv);

  return 0;

@@ -2559,9 +2703,13 @@ static void intel_power_domains_sync_hw(struct drm_i915_private *dev_priv)

mutex_lock(&power_domains->lock); for_each_power_well(dev_priv, power_well) {

• unsigned long flags = 0;
  

• power_well_lock(power_well, flags);
  

  power_well->ops->sync_hw(dev_priv, power_well); power_well->hw_enabled = power_well->ops->is_enabled(dev_priv, power_well);

• power_well_unlock(power_well, flags);
  

  } mutex_unlock(&power_domains->lock);

} @@ -3034,16 +3182,18 @@ void intel_power_domains_suspend(struct drm_i915_private *dev_priv) bxt_display_core_uninit(dev_priv); }

-static void intel_power_domains_dump_info(struct drm_i915_private *dev_priv) +static void intel_power_domains_dump_info(struct drm_i915_private *dev_priv,

• 			  const int *power_well_use)
  

{ struct i915_power_domains *power_domains = &dev_priv->power_domains; struct i915_power_well *power_well;

• int i = 0;

  for_each_power_well(dev_priv, power_well) { enum intel_display_power_domain domain;

  DRM_DEBUG_DRIVER("%-25s %d\n",

• 		 power_well->name, power_well->count);
  

• 		 power_well->name, power_well_use[i++]);
  
  

  for_each_power_domain(domain, power_well->domains) DRM_DEBUG_DRIVER(" %-23s %d\n",

@@ -3067,6 +3217,7 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv) struct i915_power_domains *power_domains = &dev_priv->power_domains; struct i915_power_well *power_well; bool dump_domain_info;

• int power_well_use[dev_priv->power_domains.power_well_count];

  mutex_lock(&power_domains->lock);

@@ -3075,6 +3226,14 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv) enum intel_display_power_domain domain; int domains_count; bool enabled;

• int well_count, i = 0;
  

• unsigned long flags = 0;
  

• power_well_lock(power_well, flags);
  

• well_count = power_well->count;
  

• enabled = power_well->ops->is_enabled(dev_priv, power_well);
  

• power_well_unlock(power_well, flags);
  

• power_well_use[i++] = well_count;
  
  

  /*

  • Power wells not belonging to any domain (like the MISC_IO

@@ -3084,20 +3243,19 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv) if (!power_well->domains) continue;

• enabled = power_well->ops->is_enabled(dev_priv, power_well);
  

• if ((power_well->count || power_well->always_on) != enabled)
  

• if ((well_count || power_well->always_on) != enabled)
  DRM_ERROR("power well %s state mismatch (refcount %d/enabled %d)",
  

• 		  power_well->name, power_well->count, enabled);
  

• 		  power_well->name, well_count, enabled);
  
  

  domains_count = 0; for_each_power_domain(domain, power_well->domains) domains_count += atomic_read(&power_domains->domain_use_count[domain]);

• if (power_well->count != domains_count) {
  

• if (well_count != domains_count) {
  DRM_ERROR("power well %s refcount/domain refcount mismatch "
  	  "(refcount %d/domains refcount %d)\n",
  

• 		  power_well->name, power_well->count,
  

• 		  domains_count);
  

• 		  power_well->name, well_count, domains_count);
  dump_domain_info = true;
  

  } }

@@ -3106,7 +3264,7 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv) static bool dumped;

if (!dumped) {

• 	intel_power_domains_dump_info(dev_priv);
  

• 	intel_power_domains_dump_info(dev_priv, power_well_use);
  dumped = true;
  

  } }

-- 2.11.0

---

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