drm/i915/pmu: Support multiple GPUs

With discrete graphics system can have both integrated and discrete GPU
handled by i915.

Currently we use a fixed name ("i915") when registering as the uncore PMU
provider which stops working in this case.

To fix this we add the PCI device name string to non-integrated devices
handled by us. Integrated devices keep the legacy name preserving
backward compatibility.

v2:
 * Detect IGP and keep legacy name. (Michal)
 * Use PCI device name as suffix. (Michal, Chris)

v3:
 * Constify the name. (Chris)
 * Use pci_domain_nr. (Chris)

v4:
 * Fix kfree_const usage. (Chris)

v5:
 * kfree_const does not work for modules. (Chris)
 * Changed is_igp helper to take i915.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191016093802.12483-1-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/i915_pmu.c

@@ -1080,6 +1080,17 @@ static void i915_pmu_unregister_cpuhp_state(struct i915_pmu *pmu)
 	cpuhp_remove_multi_state(cpuhp_slot);
 }
 
+static bool is_igp(struct drm_i915_private *i915)
+{
+	struct pci_dev *pdev = i915->drm.pdev;
+
+	/* IGP is 0000:00:02.0 */
+	return pci_domain_nr(pdev->bus) == 0 &&
+	       pdev->bus->number == 0 &&
+	       PCI_SLOT(pdev->devfn) == 2 &&
+	       PCI_FUNC(pdev->devfn) == 0;
+}
+
 void i915_pmu_register(struct drm_i915_private *i915)
 {
 	struct i915_pmu *pmu = &i915->pmu;
@@ -1110,10 +1121,19 @@ void i915_pmu_register(struct drm_i915_private *i915)
 	hrtimer_init(&pmu->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	pmu->timer.function = i915_sample;
 
-	ret = perf_pmu_register(&pmu->base, "i915", -1);
-	if (ret)
+	if (!is_igp(i915))
+		pmu->name = kasprintf(GFP_KERNEL,
+				      "i915-%s",
+				      dev_name(i915->drm.dev));
+	else
+		pmu->name = "i915";
+	if (!pmu->name)
 		goto err;
 
+	ret = perf_pmu_register(&pmu->base, pmu->name, -1);
+	if (ret)
+		goto err_name;
+
 	ret = i915_pmu_register_cpuhp_state(pmu);
 	if (ret)
 		goto err_unreg;
@@ -1122,6 +1142,9 @@ void i915_pmu_register(struct drm_i915_private *i915)
 
 err_unreg:
 	perf_pmu_unregister(&pmu->base);
+err_name:
+	if (!is_igp(i915))
+		kfree(pmu->name);
 err:
 	pmu->base.event_init = NULL;
 	free_event_attributes(pmu);
@@ -1143,5 +1166,7 @@ void i915_pmu_unregister(struct drm_i915_private *i915)
 
 	perf_pmu_unregister(&pmu->base);
 	pmu->base.event_init = NULL;
+	if (!is_igp(i915))
+		kfree(pmu->name);
 	free_event_attributes(pmu);
 }

drivers/gpu/drm/i915/i915_pmu.h

@@ -46,6 +46,10 @@ struct i915_pmu {
 	 * @base: PMU base.
 	 */
 	struct pmu base;
+	/**
+	 * @name: Name as registered with perf core.
+	 */
+	const char *name;
 	/**
 	 * @lock: Lock protecting enable mask and ref count handling.
 	 */