drm/msm/a6xx: Vote for cx gdsc from gpu driver

When a device has multiple power domains, dev->power_domain is left
empty during probe. That didn't cause any issue so far because we are
freeloading on smmu driver's vote on cx gdsc. Instead of that, create
a device_link between cx genpd device and gmu device to keep a vote from
gpu driver.

Before this patch:
localhost ~ # cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
gx_gdsc		on		0
    /devices/genpd:1:3d6a000.gmu		active		0
cx_gdsc		on		0
    /devices/platform/soc@0/3da0000.iommu	active		0

After this patch:
localhost ~ # cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
gx_gdsc		on		0
    /devices/genpd:1:3d6a000.gmu		active		0
cx_gdsc		on		0
    /devices/platform/soc@0/3da0000.iommu	active		0
    /devices/genpd:0:3d6a000.gmu		active		0
Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/516468/
Link: https://lore.kernel.org/r/20230102161757.v5.3.I7f545d8494dcdbe6e96a15fbe8aaf5bb0c003d50@changeidSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/a6xx_gmu.c

@@ -1482,6 +1482,12 @@ void a6xx_gmu_remove(struct a6xx_gpu *a6xx_gpu)
 
 	pm_runtime_force_suspend(gmu->dev);
 
+	/*
+	 * Since cxpd is a virt device, the devlink with gmu-dev will be removed
+	 * automatically when we do detach
+	 */
+	dev_pm_domain_detach(gmu->cxpd, false);
+
 	if (!IS_ERR_OR_NULL(gmu->gxpd)) {
 		pm_runtime_disable(gmu->gxpd);
 		dev_pm_domain_detach(gmu->gxpd, false);
@@ -1608,8 +1614,10 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 
 	if (adreno_is_a650_family(adreno_gpu)) {
 		gmu->rscc = a6xx_gmu_get_mmio(pdev, "rscc");
-		if (IS_ERR(gmu->rscc))
+		if (IS_ERR(gmu->rscc)) {
+			ret = -ENODEV;
 			goto err_mmio;
+		}
 	} else {
 		gmu->rscc = gmu->mmio + 0x23000;
 	}
@@ -1618,8 +1626,22 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 	gmu->hfi_irq = a6xx_gmu_get_irq(gmu, pdev, "hfi", a6xx_hfi_irq);
 	gmu->gmu_irq = a6xx_gmu_get_irq(gmu, pdev, "gmu", a6xx_gmu_irq);
 
-	if (gmu->hfi_irq < 0 || gmu->gmu_irq < 0)
+	if (gmu->hfi_irq < 0 || gmu->gmu_irq < 0) {
+		ret = -ENODEV;
+		goto err_mmio;
+	}
+
+	gmu->cxpd = dev_pm_domain_attach_by_name(gmu->dev, "cx");
+	if (IS_ERR(gmu->cxpd)) {
+		ret = PTR_ERR(gmu->cxpd);
 		goto err_mmio;
+	}
+
+	if (!device_link_add(gmu->dev, gmu->cxpd,
+					DL_FLAG_PM_RUNTIME)) {
+		ret = -ENODEV;
+		goto detach_cxpd;
+	}
 
 	/*
 	 * Get a link to the GX power domain to reset the GPU in case of GMU
@@ -1637,6 +1659,9 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 
 	return 0;
 
+detach_cxpd:
+	dev_pm_domain_detach(gmu->cxpd, false);
+
 err_mmio:
 	iounmap(gmu->mmio);
 	if (platform_get_resource_byname(pdev, IORESOURCE_MEM, "rscc"))
@@ -1644,8 +1669,6 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 	free_irq(gmu->gmu_irq, gmu);
 	free_irq(gmu->hfi_irq, gmu);
 
-	ret = -ENODEV;
-
 err_memory:
 	a6xx_gmu_memory_free(gmu);
 err_put_device:

drivers/gpu/drm/msm/adreno/a6xx_gmu.h

@@ -56,6 +56,7 @@ struct a6xx_gmu {
 	int gmu_irq;
 
 	struct device *gxpd;
+	struct device *cxpd;
 
 	int idle_level;