drm/v3d: Add module parameter to enable MMU error logging

MMU error messages are useful to help developers quickly identify
issues in userspace graphics drivers, but always printing them can
swamp the kernel log.

Add a module parameter, ``debug_mmu``, to gate MMU error logging.
Logging is disabled by default and can be enabled when needed with
``v3d.debug_mmu=1``.

Signed-off-by: Maíra Canal <mairacanal@riseup.net>

Author: mairacanal

drivers/gpu/drm/v3d/v3d_drv.c

@@ -47,6 +47,10 @@ module_param_named(super_pages, super_pages, bool, 0400);
 MODULE_PARM_DESC(super_pages, "Enable/Disable Super Pages support.");
 #endif
 
+bool debug_mmu;
+module_param(debug_mmu, bool, 0644);
+MODULE_PARM_DESC(debug_mmu, "Enable/Disable MMU error logging");
+
 static int v3d_get_param_ioctl(struct drm_device *dev, void *data,
 			       struct drm_file *file_priv)
 {

drivers/gpu/drm/v3d/v3d_drv.h

@@ -589,6 +589,7 @@ int v3d_submit_cpu_ioctl(struct drm_device *dev, void *data,
 			 struct drm_file *file_priv);
 
 /* v3d_irq.c */
+extern bool debug_mmu;
 int v3d_irq_init(struct v3d_dev *v3d);
 void v3d_irq_enable(struct v3d_dev *v3d);
 void v3d_irq_disable(struct v3d_dev *v3d);

drivers/gpu/drm/v3d/v3d_irq.c

@@ -183,7 +183,7 @@ v3d_hub_irq(int irq, void *arg)
 			"GMP",
 		};
 		const char *client = "?";
-		static int logged_error;
+		static bool logged_error;
 
 		V3D_WRITE(V3D_MMU_CTL, V3D_READ(V3D_MMU_CTL));
 
@@ -193,16 +193,18 @@ v3d_hub_irq(int irq, void *arg)
 				client = v3d41_axi_ids[axi_id];
 		}
 
-		if (!logged_error)
-		dev_err(v3d->drm.dev, "MMU error from client %s (%d) at 0x%llx%s%s%s\n",
-			client, axi_id, (long long)vio_addr,
-			((intsts & V3D_HUB_INT_MMU_WRV) ?
-			 ", write violation" : ""),
-			((intsts & V3D_HUB_INT_MMU_PTI) ?
-			 ", pte invalid" : ""),
-			((intsts & V3D_HUB_INT_MMU_CAP) ?
-			 ", cap exceeded" : ""));
-		logged_error = 1;
+		if (!logged_error || debug_mmu) {
+			dev_err(v3d->drm.dev, "MMU error from client %s (%d) at 0x%llx%s%s%s\n",
+				client, axi_id, (long long)vio_addr,
+				((intsts & V3D_HUB_INT_MMU_WRV) ?
+				 ", write violation" : ""),
+				((intsts & V3D_HUB_INT_MMU_PTI) ?
+				 ", pte invalid" : ""),
+				((intsts & V3D_HUB_INT_MMU_CAP) ?
+				 ", cap exceeded" : ""));
+		}
+		logged_error = true;
+
 		status = IRQ_HANDLED;
 	}