drm/amdgpu: Add autodump debugfs node for gpu reset v8

When GPU got timeout, it would notify an interested part
of an opportunity to dump info before actual GPU reset.

A usermode app would open 'autodump' node under debugfs system
and poll() for readable/writable. When a GPU reset is due,
amdgpu would notify usermode app through wait_queue_head and give
it 10 minutes to dump info.

After usermode app has done its work, this 'autodump' node is closed.
On node closure, amdgpu gets to know the dump is done through
the completion that is triggered in release().

There is no write or read callback because necessary info can be
obtained through dmesg and umr. Messages back and forth between
usermode app and amdgpu are unnecessary.

v2: (1) changed 'registered' to 'app_listening'
    (2) add a mutex in open() to prevent race condition

v3 (chk): grab the reset lock to avoid race in autodump_open,
          rename debugfs file to amdgpu_autodump,
          provide autodump_read as well,
          style and code cleanups

v4: add 'bool app_listening' to differentiate situations, so that
    the node can be reopened; also, there is no need to wait for
    completion when no app is waiting for a dump.

v5: change 'bool app_listening' to 'enum amdgpu_autodump_state'
    add 'app_state_mutex' for race conditions:
	(1)Only 1 user can open this file node
	(2)wait_dump() can only take effect after poll() executed.
	(3)eliminated the race condition between release() and
	   wait_dump()

v6: removed 'enum amdgpu_autodump_state' and 'app_state_mutex'
    removed state checking in amdgpu_debugfs_wait_dump
    Improve on top of version 3 so that the node can be reopened.

v7: move reinit_completion into open() so that only one user
    can open it.

v8: remove complete_all() from amdgpu_debugfs_wait_dump().
Signed-off-by: Jiange Zhao <Jiange.Zhao@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -989,6 +989,8 @@ struct amdgpu_device {
 	char				product_number[16];
 	char				product_name[32];
 	char				serial[16];
+
+	struct amdgpu_autodump		autodump;
 };
 
 static inline struct amdgpu_device *amdgpu_ttm_adev(struct ttm_bo_device *bdev)

drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

@@ -27,7 +27,7 @@
 #include <linux/pci.h>
 #include <linux/uaccess.h>
 #include <linux/pm_runtime.h>
-
+#include <linux/poll.h>
 #include <drm/drm_debugfs.h>
 
 #include "amdgpu.h"
@@ -74,8 +74,82 @@ int amdgpu_debugfs_add_files(struct amdgpu_device *adev,
 	return 0;
 }
 
+int amdgpu_debugfs_wait_dump(struct amdgpu_device *adev)
+{
+#if defined(CONFIG_DEBUG_FS)
+	unsigned long timeout = 600 * HZ;
+	int ret;
+
+	wake_up_interruptible(&adev->autodump.gpu_hang);
+
+	ret = wait_for_completion_interruptible_timeout(&adev->autodump.dumping, timeout);
+	if (ret == 0) {
+		pr_err("autodump: timeout, move on to gpu recovery\n");
+		return -ETIMEDOUT;
+	}
+#endif
+	return 0;
+}
+
 #if defined(CONFIG_DEBUG_FS)
 
+static int amdgpu_debugfs_autodump_open(struct inode *inode, struct file *file)
+{
+	struct amdgpu_device *adev = inode->i_private;
+	int ret;
+
+	file->private_data = adev;
+
+	mutex_lock(&adev->lock_reset);
+	if (adev->autodump.dumping.done) {
+		reinit_completion(&adev->autodump.dumping);
+		ret = 0;
+	} else {
+		ret = -EBUSY;
+	}
+	mutex_unlock(&adev->lock_reset);
+
+	return ret;
+}
+
+static int amdgpu_debugfs_autodump_release(struct inode *inode, struct file *file)
+{
+	struct amdgpu_device *adev = file->private_data;
+
+	complete_all(&adev->autodump.dumping);
+	return 0;
+}
+
+static unsigned int amdgpu_debugfs_autodump_poll(struct file *file, struct poll_table_struct *poll_table)
+{
+	struct amdgpu_device *adev = file->private_data;
+
+	poll_wait(file, &adev->autodump.gpu_hang, poll_table);
+
+	if (adev->in_gpu_reset)
+		return POLLIN | POLLRDNORM | POLLWRNORM;
+
+	return 0;
+}
+
+static const struct file_operations autodump_debug_fops = {
+	.owner = THIS_MODULE,
+	.open = amdgpu_debugfs_autodump_open,
+	.poll = amdgpu_debugfs_autodump_poll,
+	.release = amdgpu_debugfs_autodump_release,
+};
+
+static void amdgpu_debugfs_autodump_init(struct amdgpu_device *adev)
+{
+	init_completion(&adev->autodump.dumping);
+	complete_all(&adev->autodump.dumping);
+	init_waitqueue_head(&adev->autodump.gpu_hang);
+
+	debugfs_create_file("amdgpu_autodump", 0600,
+		adev->ddev->primary->debugfs_root,
+		adev, &autodump_debug_fops);
+}
+
 /**
  * amdgpu_debugfs_process_reg_op - Handle MMIO register reads/writes
  *
@@ -1434,6 +1508,8 @@ int amdgpu_debugfs_init(struct amdgpu_device *adev)
 
 	amdgpu_ras_debugfs_create_all(adev);
 
+	amdgpu_debugfs_autodump_init(adev);
+
 	return amdgpu_debugfs_add_files(adev, amdgpu_debugfs_list,
 					ARRAY_SIZE(amdgpu_debugfs_list));
 }

drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h

@@ -31,6 +31,11 @@ struct amdgpu_debugfs {
 	unsigned		num_files;
 };
 
+struct amdgpu_autodump {
+	struct completion		dumping;
+	struct wait_queue_head		gpu_hang;
+};
+
 int amdgpu_debugfs_regs_init(struct amdgpu_device *adev);
 int amdgpu_debugfs_init(struct amdgpu_device *adev);
 void amdgpu_debugfs_fini(struct amdgpu_device *adev);
@@ -40,3 +45,4 @@ int amdgpu_debugfs_add_files(struct amdgpu_device *adev,
 int amdgpu_debugfs_fence_init(struct amdgpu_device *adev);
 int amdgpu_debugfs_firmware_init(struct amdgpu_device *adev);
 int amdgpu_debugfs_gem_init(struct amdgpu_device *adev);
+int amdgpu_debugfs_wait_dump(struct amdgpu_device *adev);

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -3927,6 +3927,8 @@ static int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
 	int i, r = 0;
 	bool need_full_reset  = *need_full_reset_arg;
 
+	amdgpu_debugfs_wait_dump(adev);
+
 	/* block all schedulers and reset given job's ring */
 	for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
 		struct amdgpu_ring *ring = adev->rings[i];