drm/vc4: hvs: Provide a function to initialize the HVS structure

We'll need to initialize the HVS structure without a backing device to
create a mock we'll use for testing.

Split the structure initialization part into a separate function.
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20221123-rpi-kunit-tests-v3-16-4615a663a84a@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_drv.h

@@ -1009,6 +1009,7 @@ void vc4_irq_reset(struct drm_device *dev);
 
 /* vc4_hvs.c */
 extern struct platform_driver vc4_hvs_driver;
+struct vc4_hvs *__vc4_hvs_alloc(struct vc4_dev *vc4, struct platform_device *pdev);
 void vc4_hvs_stop_channel(struct vc4_hvs *hvs, unsigned int output);
 int vc4_hvs_get_fifo_from_output(struct vc4_hvs *hvs, unsigned int output);
 u8 vc4_hvs_get_fifo_frame_count(struct vc4_hvs *hvs, unsigned int fifo);

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -768,6 +768,46 @@ int vc4_hvs_debugfs_init(struct drm_minor *minor)
 	return 0;
 }
 
+struct vc4_hvs *__vc4_hvs_alloc(struct vc4_dev *vc4, struct platform_device *pdev)
+{
+	struct drm_device *drm = &vc4->base;
+	struct vc4_hvs *hvs;
+
+	hvs = drmm_kzalloc(drm, sizeof(*hvs), GFP_KERNEL);
+	if (!hvs)
+		return ERR_PTR(-ENOMEM);
+
+	hvs->vc4 = vc4;
+	hvs->pdev = pdev;
+
+	spin_lock_init(&hvs->mm_lock);
+
+	/* Set up the HVS display list memory manager.  We never
+	 * overwrite the setup from the bootloader (just 128b out of
+	 * our 16K), since we don't want to scramble the screen when
+	 * transitioning from the firmware's boot setup to runtime.
+	 */
+	drm_mm_init(&hvs->dlist_mm,
+		    HVS_BOOTLOADER_DLIST_END,
+		    (SCALER_DLIST_SIZE >> 2) - HVS_BOOTLOADER_DLIST_END);
+
+	/* Set up the HVS LBM memory manager.  We could have some more
+	 * complicated data structure that allowed reuse of LBM areas
+	 * between planes when they don't overlap on the screen, but
+	 * for now we just allocate globally.
+	 */
+	if (!vc4->is_vc5)
+		/* 48k words of 2x12-bit pixels */
+		drm_mm_init(&hvs->lbm_mm, 0, 48 * 1024);
+	else
+		/* 60k words of 4x12-bit pixels */
+		drm_mm_init(&hvs->lbm_mm, 0, 60 * 1024);
+
+	vc4->hvs = hvs;
+
+	return hvs;
+}
+
 static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 {
 	struct platform_device *pdev = to_platform_device(dev);
@@ -778,11 +818,9 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 	u32 dispctrl;
 	u32 reg;
 
-	hvs = drmm_kzalloc(drm, sizeof(*hvs), GFP_KERNEL);
-	if (!hvs)
-		return -ENOMEM;
-	hvs->vc4 = vc4;
-	hvs->pdev = pdev;
+	hvs = __vc4_hvs_alloc(vc4, NULL);
+	if (IS_ERR(hvs))
+		return PTR_ERR(hvs);
 
 	hvs->regs = vc4_ioremap_regs(pdev, 0);
 	if (IS_ERR(hvs->regs))
@@ -835,29 +873,6 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 	else
 		hvs->dlist = hvs->regs + SCALER5_DLIST_START;
 
-	spin_lock_init(&hvs->mm_lock);
-
-	/* Set up the HVS display list memory manager.  We never
-	 * overwrite the setup from the bootloader (just 128b out of
-	 * our 16K), since we don't want to scramble the screen when
-	 * transitioning from the firmware's boot setup to runtime.
-	 */
-	drm_mm_init(&hvs->dlist_mm,
-		    HVS_BOOTLOADER_DLIST_END,
-		    (SCALER_DLIST_SIZE >> 2) - HVS_BOOTLOADER_DLIST_END);
-
-	/* Set up the HVS LBM memory manager.  We could have some more
-	 * complicated data structure that allowed reuse of LBM areas
-	 * between planes when they don't overlap on the screen, but
-	 * for now we just allocate globally.
-	 */
-	if (!vc4->is_vc5)
-		/* 48k words of 2x12-bit pixels */
-		drm_mm_init(&hvs->lbm_mm, 0, 48 * 1024);
-	else
-		/* 60k words of 4x12-bit pixels */
-		drm_mm_init(&hvs->lbm_mm, 0, 60 * 1024);
-
 	/* Upload filter kernels.  We only have the one for now, so we
 	 * keep it around for the lifetime of the driver.
 	 */
@@ -867,8 +882,6 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 	if (ret)
 		return ret;
 
-	vc4->hvs = hvs;
-
 	reg = HVS_READ(SCALER_DISPECTRL);
 	reg &= ~SCALER_DISPECTRL_DSP2_MUX_MASK;
 	HVS_WRITE(SCALER_DISPECTRL,