drm: mali-dp: Add debugfs file for reporting internal errors

Status register contains a lot of bits for reporting internal errors
inside Mali DP. Currently, we just silently ignore all of the errors,
that doesn't help when we are investigating different bugs, especially
on the FPGA models which have a lot of constraints, so we could easily
end up in AXI or underrun errors.

Add a new file called debug that contains an aggregate of the
errors reported by the Mali DP hardware.

E.g:
[root@alarm ~]# cat /sys/kernel/debug/dri/1/debug
[DE] num_errors : 167
[DE] last_error_status  : 0x00000001
[DE] last_error_vblank : 385
[SE] num_errors : 3
[SE] last_error_status  : 0x00e23001
[SE] last_error_vblank : 201

Changes since v2:
- Add lock to protect the errors stats.
- Add possibility to reset the error stats by writing anything to the
  debug file.

Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
index 078b232c91ab..9b710f6999ed 100644
--- a/drivers/gpu/drm/arm/malidp_drv.c
+++ b/drivers/gpu/drm/arm/malidp_drv.c
@@ -17,6 +17,7 @@
 #include <linux/of_graph.h>
 #include <linux/of_reserved_mem.h>
 #include <linux/pm_runtime.h>
+#include <linux/debugfs.h>
 
 #include <drm/drmP.h>
 #include <drm/drm_atomic.h>
@@ -344,6 +345,106 @@ static int malidp_dumb_create(struct drm_file *file_priv,
 	return drm_gem_cma_dumb_create_internal(file_priv, drm, args);
 }
 
+#ifdef CONFIG_DEBUG_FS
+
+static void malidp_error_stats_init(struct malidp_error_stats *error_stats)
+{
+	error_stats->num_errors = 0;
+	error_stats->last_error_status = 0;
+	error_stats->last_error_vblank = -1;
+}
+
+void malidp_error(struct malidp_drm *malidp,
+		  struct malidp_error_stats *error_stats, u32 status,
+		  u64 vblank)
+{
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&malidp->errors_lock, irqflags);
+	error_stats->last_error_status = status;
+	error_stats->last_error_vblank = vblank;
+	error_stats->num_errors++;
+	spin_unlock_irqrestore(&malidp->errors_lock, irqflags);
+}
+
+void malidp_error_stats_dump(const char *prefix,
+			     struct malidp_error_stats error_stats,
+			     struct seq_file *m)
+{
+	seq_printf(m, "[%s] num_errors : %d\n", prefix,
+		   error_stats.num_errors);
+	seq_printf(m, "[%s] last_error_status  : 0x%08x\n", prefix,
+		   error_stats.last_error_status);
+	seq_printf(m, "[%s] last_error_vblank : %lld\n", prefix,
+		   error_stats.last_error_vblank);
+}
+
+static int malidp_show_stats(struct seq_file *m, void *arg)
+{
+	struct drm_device *drm = m->private;
+	struct malidp_drm *malidp = drm->dev_private;
+	unsigned long irqflags;
+	struct malidp_error_stats de_errors, se_errors;
+
+	spin_lock_irqsave(&malidp->errors_lock, irqflags);
+	de_errors = malidp->de_errors;
+	se_errors = malidp->se_errors;
+	spin_unlock_irqrestore(&malidp->errors_lock, irqflags);
+	malidp_error_stats_dump("DE", de_errors, m);
+	malidp_error_stats_dump("SE", se_errors, m);
+	return 0;
+}
+
+static int malidp_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, malidp_show_stats, inode->i_private);
+}
+
+static ssize_t malidp_debugfs_write(struct file *file, const char __user *ubuf,
+				    size_t len, loff_t *offp)
+{
+	struct seq_file *m = file->private_data;
+	struct drm_device *drm = m->private;
+	struct malidp_drm *malidp = drm->dev_private;
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&malidp->errors_lock, irqflags);
+	malidp_error_stats_init(&malidp->de_errors);
+	malidp_error_stats_init(&malidp->se_errors);
+	spin_unlock_irqrestore(&malidp->errors_lock, irqflags);
+	return len;
+}
+
+static const struct file_operations malidp_debugfs_fops = {
+	.owner = THIS_MODULE,
+	.open = malidp_debugfs_open,
+	.read = seq_read,
+	.write = malidp_debugfs_write,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+static int malidp_debugfs_init(struct drm_minor *minor)
+{
+	struct malidp_drm *malidp = minor->dev->dev_private;
+	struct dentry *dentry = NULL;
+
+	malidp_error_stats_init(&malidp->de_errors);
+	malidp_error_stats_init(&malidp->se_errors);
+	spin_lock_init(&malidp->errors_lock);
+	dentry = debugfs_create_file("debug",
+				     S_IRUGO | S_IWUSR,
+				     minor->debugfs_root, minor->dev,
+				     &malidp_debugfs_fops);
+	if (!dentry) {
+		DRM_ERROR("Cannot create debug file\n");
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+#endif //CONFIG_DEBUG_FS
+
 static struct drm_driver malidp_driver = {
 	.driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC |
 			   DRIVER_PRIME,
@@ -360,6 +461,9 @@ static struct drm_driver malidp_driver = {
 	.gem_prime_vmap = drm_gem_cma_prime_vmap,
 	.gem_prime_vunmap = drm_gem_cma_prime_vunmap,
 	.gem_prime_mmap = drm_gem_cma_prime_mmap,
+#ifdef CONFIG_DEBUG_FS
+	.debugfs_init = malidp_debugfs_init,
+#endif
 	.fops = &fops,
 	.name = "mali-dp",
 	.desc = "ARM Mali Display Processor driver",