Re: [PATCH] drm/xe/debugfs: Add support for gt synchronous force reset

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

"Poosa, Karthik" <karthik.poosa@intel.com> writes:

> Hi Anshuman,
>
> Please find my comments inline below.
>
> Thanks,
>
> Karthik.
>
> On 01-01-2024 20:07, Gupta, Anshuman wrote:
>>
>>> -----Original Message-----
>>> From: Poosa, Karthik <karthik.poosa@intel.com>
>>> Sent: Sunday, December 31, 2023 8:18 PM
>>> To: intel-xe@lists.freedesktop.org
>>> Cc: Gupta, Anshuman <anshuman.gupta@intel.com>; Nilawar, Badal
>>> <badal.nilawar@intel.com>; Brost, Matthew <matthew.brost@intel.com>;
>>> Vivi, Rodrigo <rodrigo.vivi@intel.com>; Poosa, Karthik
>>> <karthik.poosa@intel.com>
>>> Subject: [PATCH] drm/xe/debugfs: Add support for gt synchronous force reset
>>>
>>> This support added as igt test freq_reset_multiple fails sporadically in case
>>> xe_guc_pc is not started.
>>> A completion is added in force_reset for this.
>>> Writing non-zero to force_reset debugfs entry does synchronous reset.
>> We need IGT patch as well for this patch.
>>> v2:
>>> - Changed wait for completion to interruptible (Anshuman).
>>> - Moved timeout to xe_gt.h (Anshuman).
>>> - Created a debugfs for updating timeout (Rodrigo).
>>>
>>> v3:
>>> - Update force_reset debugfs with write support.
>>>    value 0 -> async reset, non-zero -> sync reset (Matthew Brost).
>>>
>>> Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
>>> ---
>>>   drivers/gpu/drm/xe/xe_gt.c         |  2 +
>>>   drivers/gpu/drm/xe/xe_gt_debugfs.c | 72
>>> ++++++++++++++++++++++++++++--  drivers/gpu/drm/xe/xe_gt_debugfs.h
>>> |  3 ++
>>>   drivers/gpu/drm/xe/xe_gt_types.h   |  8 ++++
>>>   4 files changed, 82 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c index
>>> 3af2adec1295..c8d2c18b0c62 100644
>>> --- a/drivers/gpu/drm/xe/xe_gt.c
>>> +++ b/drivers/gpu/drm/xe/xe_gt.c
>>> @@ -65,6 +65,7 @@ struct xe_gt *xe_gt_alloc(struct xe_tile *tile)
>>>
>>>   	gt->tile = tile;
>>>   	gt->ordered_wq = alloc_ordered_workqueue("gt-ordered-wq", 0);
>>> +	init_completion(&gt->reset.done);
>>>
>>>   	return gt;
>>>   }
>>> @@ -633,6 +634,7 @@ static int gt_reset(struct xe_gt *gt)
>>>   	xe_device_mem_access_put(gt_to_xe(gt));
>>>   	XE_WARN_ON(err);
>>>
>>> +	complete(&gt->reset.done);
>>>   	xe_gt_info(gt, "reset done\n");
>>>
>>>   	return 0;
>>> diff --git a/drivers/gpu/drm/xe/xe_gt_debugfs.c
>>> b/drivers/gpu/drm/xe/xe_gt_debugfs.c
>>> index c4b67cf09f8f..3518ab89ccfc 100644
>>> --- a/drivers/gpu/drm/xe/xe_gt_debugfs.c
>>> +++ b/drivers/gpu/drm/xe/xe_gt_debugfs.c
>>> @@ -55,15 +55,71 @@ static int hw_engines(struct seq_file *m, void *data)
>>>   	return 0;
>>>   }
>>>
>>> -static int force_reset(struct seq_file *m, void *data)
>>> +static int force_reset(struct xe_gt *gt, bool is_sync)
>>>   {
>>> -	struct xe_gt *gt = node_to_gt(m->private);
>>> +	struct xe_device *xe = gt_to_xe(gt);
>>> +	long ret;
>>>
>>>   	xe_gt_reset_async(gt);
>>>
>>> +	if (is_sync) {
>>> +		drm_info(&xe->drm, "waiting for gt reset completion");
>>> +		ret = wait_for_completion_interruptible_timeout(&gt-
>>>> reset.done,
>>> +							msecs_to_jiffies(gt-
>>>> reset.timeout_ms));
>>> +		if (ret <= 0) {
>>> +			drm_err(&xe->drm, "gt reset timed out/interrputed,
>>> ret %ld\n", ret);
>>> +			return -ETIMEDOUT;
>>> +		}
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +ssize_t force_reset_write(struct file *f, const char __user *buf,
>>> +size_t len, loff_t *offset) {
>>> +	struct xe_gt *gt = file_inode(f)->i_private;
>>> +	struct xe_device *xe = gt_to_xe(gt);
>>> +	char arg_str[5];
>>> +	size_t size;
>>> +	unsigned long arg;
>>> +	int ret;
>>> +
>>> +	size = min(sizeof(arg_str)-1, len);
>>> +	arg = copy_from_user((void *)arg_str, buf, size);
>>> +	if (arg < 0) {
>>> +		drm_err(&xe->drm, "reading force_reset arg failed, ret %ld",
>>> arg);
>>> +		return arg;
>>> +	}
>>> +	arg_str[size] = '\0';
>>> +
>>> +	ret = kstrtoul(arg_str, 0, &arg);
>>> +	if (ret) {
>>> +		drm_err(&xe->drm, "force_reset arg parse failed, ret %d", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	ret = force_reset(gt, (arg && 1));
>> How about  !!arg
> && will use a single instruction.
>
> but !! will happen with 2 instructions, so I think && would be better.

This is not in a hotpath, more readable is better.
-Mika


>
>>   > +	if (ret != 0)  {
>>> +		drm_err(&xe->drm, "force_reset failed, ret %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +	return len;
>>> +}
>>> +
>>> +ssize_t force_reset_read(struct file *f, char __user *buf, size_t len,
>>> +loff_t *offset) {
>>> +	struct xe_gt *gt = file_inode(f)->i_private;
>>> +
>>> +	force_reset(gt, 0);
>>>   	return 0;
>>>   }
>>>
>>> +static const struct file_operations force_reset_fops = {
>>> +	.owner = THIS_MODULE,
>>> +	.write = force_reset_write,
>>> +	.read = force_reset_read,
>>> +};
>>> +
>>>   static int sa_info(struct seq_file *m, void *data)  {
>>>   	struct xe_tile *tile = gt_to_tile(node_to_gt(m->private));
>>> @@ -192,7 +248,6 @@ static int vecs_default_lrc(struct seq_file *m, void
>>> *data)
>>>
>>>   static const struct drm_info_list debugfs_list[] = {
>>>   	{"hw_engines", hw_engines, 0},
>>> -	{"force_reset", force_reset, 0},
>>>   	{"sa_info", sa_info, 0},
>>>   	{"topology", topology, 0},
>>>   	{"steering", steering, 0},
>>> @@ -245,5 +300,16 @@ void xe_gt_debugfs_register(struct xe_gt *gt)
>>>   				 ARRAY_SIZE(debugfs_list),
>>>   				 root, minor);
>>>
>>> +	gt->reset.fr_dentry = debugfs_create_file("force_reset", 0600, root,
>>> xe,
>>> +			    &force_reset_fops);
>> Please use DEFINE_SHOW_STORE_ATTRIBUTE here to create rw debugfs entry.
>> Use force_reset_show and force_reset_restore function name.
>>> +	if (!gt->reset.fr_dentry)
>>> +		drm_warn(&xe->drm, "force_reset debugfs file creation
>>> failed");
>>> +	d_inode(gt->reset.fr_dentry)->i_private = gt;
>>> +
>>> +	debugfs_create_u32("gt_reset_timeout_ms", 0600, root,
>>> +					&gt->reset.timeout_ms);
>>> +	/* set a default timeout value */
>>> +	gt->reset.timeout_ms = 1000;
>> xe_gt_debugfs_register() should only do the job of debugfs registration.
>> This is odd here.
>
> Shall I move this to xe_gt_alloc (xe_gt.c), where gt is allocated and 
> initialized.
>
>>> +
>>>   	xe_uc_debugfs_register(&gt->uc, root);  } diff --git
>>> a/drivers/gpu/drm/xe/xe_gt_debugfs.h
>>> b/drivers/gpu/drm/xe/xe_gt_debugfs.h
>>> index 5a329f118a57..40adcf1822c6 100644
>>> --- a/drivers/gpu/drm/xe/xe_gt_debugfs.h
>>> +++ b/drivers/gpu/drm/xe/xe_gt_debugfs.h
>>> @@ -6,8 +6,11 @@
>>>   #ifndef _XE_GT_DEBUGFS_H_
>>>   #define _XE_GT_DEBUGFS_H_
>>>
>>> +#include <linux/fs.h>
>>>   struct xe_gt;
>>>
>>>   void xe_gt_debugfs_register(struct xe_gt *gt);
>>> +ssize_t force_reset_write(struct file *f, const char __user *buf,
>>> +size_t len, loff_t *offset); ssize_t force_reset_read(struct file *f,
>>> +char __user *buf, size_t len, loff_t *offset);
>>>
>>>   #endif
>>> diff --git a/drivers/gpu/drm/xe/xe_gt_types.h
>>> b/drivers/gpu/drm/xe/xe_gt_types.h
>>> index f74684660475..d6134215094b 100644
>>> --- a/drivers/gpu/drm/xe/xe_gt_types.h
>>> +++ b/drivers/gpu/drm/xe/xe_gt_types.h
>>> @@ -148,6 +148,14 @@ struct xe_gt {
>>>   		 * code to safely flush all code paths
>>>   		 */
>>>   		struct work_struct worker;
>>> +		/** @done : completion for GT reset */
>>> +		struct completion done;
>>> +		/** @timeout_ms : gt synchronous reset timeout in ms */
>>> +		u32 timeout_ms;
>>> +		/** @dentry: dentry for force_reset */
>>> +		struct dentry *fr_dentry;
>>> +		/** @is_sync_reset : gt reset is synchronous */
>>> +		//bool is_sync_reset;
>> Remove thus unused var.
>>
>> Thanks,
>> Anshuman Gupta.
>>>   	} reset;
>>>
>>>   	/** @tlb_invalidation: TLB invalidation state */
>>> --
>>> 2.25.1