drm/vc4: dsi: Release workaround buffer and DMA

On Pi0-3 the driver allocates a buffer and requests a DMA channel
because the ARM can't write to DSI1's registers directly.

However, we never release that buffer or channel. Let's add a
device-managed action to release each.

Fixes: 4078f575 ("drm/vc4: Add DSI driver")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20220613144800.326124-12-maxime@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_dsi.c

@@ -1487,13 +1487,29 @@ vc4_dsi_init_phy_clocks(struct vc4_dsi *dsi)
 				      dsi->clk_onecell);
 }
 
+static void vc4_dsi_dma_mem_release(void *ptr)
+{
+	struct vc4_dsi *dsi = ptr;
+	struct device *dev = &dsi->pdev->dev;
+
+	dma_free_coherent(dev, 4, dsi->reg_dma_mem, dsi->reg_dma_paddr);
+	dsi->reg_dma_mem = NULL;
+}
+
+static void vc4_dsi_dma_chan_release(void *ptr)
+{
+	struct vc4_dsi *dsi = ptr;
+
+	dma_release_channel(dsi->reg_dma_chan);
+	dsi->reg_dma_chan = NULL;
+}
+
 static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
 {
 	struct platform_device *pdev = to_platform_device(dev);
 	struct drm_device *drm = dev_get_drvdata(master);
 	struct vc4_dsi *dsi = dev_get_drvdata(dev);
 	struct vc4_dsi_encoder *vc4_dsi_encoder;
-	dma_cap_mask_t dma_mask;
 	int ret;
 
 	dsi->variant = of_device_get_match_data(dev);
@@ -1527,6 +1543,8 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
 	 * so set up a channel for talking to it.
 	 */
 	if (dsi->variant->broken_axi_workaround) {
+		dma_cap_mask_t dma_mask;
+
 		dsi->reg_dma_mem = dma_alloc_coherent(dev, 4,
 						      &dsi->reg_dma_paddr,
 						      GFP_KERNEL);
@@ -1535,8 +1553,13 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
 			return -ENOMEM;
 		}
 
+		ret = devm_add_action_or_reset(dev, vc4_dsi_dma_mem_release, dsi);
+		if (ret)
+			return ret;
+
 		dma_cap_zero(dma_mask);
 		dma_cap_set(DMA_MEMCPY, dma_mask);
+
 		dsi->reg_dma_chan = dma_request_chan_by_mask(&dma_mask);
 		if (IS_ERR(dsi->reg_dma_chan)) {
 			ret = PTR_ERR(dsi->reg_dma_chan);
@@ -1546,6 +1569,10 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
 			return ret;
 		}
 
+		ret = devm_add_action_or_reset(dev, vc4_dsi_dma_chan_release, dsi);
+		if (ret)
+			return ret;
+
 		/* Get the physical address of the device's registers.  The
 		 * struct resource for the regs gives us the bus address
 		 * instead.