Add sysfs knobs for the following parameters:

    dev_freq_timeout_ms: for clearing up the device frequency limit when
                        latency-intensive block IO is complete

This can be used to prevent delayed responses to latency-sensitive block
I/O operations when storage device operate at low frequency. By
implementing the "dev_freq_timeout_ms", it automatically restores device
frequency constraints throug PM QoS.

Signed-off-by: Wang Jianzheng <wangjianzheng@vivo.com>
---
 block/genhd.c          | 23 +++++++++++++++++++++++
 include/linux/blkdev.h |  2 ++
 2 files changed, 25 insertions(+)

diff --git a/block/genhd.c b/block/genhd.c
index 9bbc38d12792..9462a81501a8 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1159,6 +1159,27 @@ static ssize_t partscan_show(struct device *dev,
 	return sysfs_emit(buf, "%u\n", disk_has_partscan(dev_to_disk(dev)));
 }
 
+static ssize_t dev_freq_timeout_ms_show(struct device *dev,
+					 struct device_attribute *attr, char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+
+	return sprintf(buf, "%d\n", disk->dev_freq_timeout);
+}
+
+static ssize_t dev_freq_timeout_ms_store(struct device *dev,
+					  struct device_attribute *attr,
+					  const char *buf, size_t count)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	int i;
+
+	if (count > 0 && !kstrtoint(buf, 10, &i))
+		disk->dev_freq_timeout = i;
+
+	return count;
+}
+
 static DEVICE_ATTR(range, 0444, disk_range_show, NULL);
 static DEVICE_ATTR(ext_range, 0444, disk_ext_range_show, NULL);
 static DEVICE_ATTR(removable, 0444, disk_removable_show, NULL);
@@ -1173,6 +1194,7 @@ static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
 static DEVICE_ATTR(badblocks, 0644, disk_badblocks_show, disk_badblocks_store);
 static DEVICE_ATTR(diskseq, 0444, diskseq_show, NULL);
 static DEVICE_ATTR(partscan, 0444, partscan_show, NULL);
+static DEVICE_ATTR_RW(dev_freq_timeout_ms);
 
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 ssize_t part_fail_show(struct device *dev,
@@ -1224,6 +1246,7 @@ static struct attribute *disk_attrs[] = {
 	&dev_attr_events_poll_msecs.attr,
 	&dev_attr_diskseq.attr,
 	&dev_attr_partscan.attr,
+	&dev_attr_dev_freq_timeout_ms.attr,
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 	&dev_attr_fail.attr,
 #endif
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index fe1797bbec42..950ad047dd81 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -213,6 +213,8 @@ struct gendisk {
 	u64 diskseq;
 	blk_mode_t open_mode;
 
+	int dev_freq_timeout;
+
 	/*
 	 * Independent sector access ranges. This is always NULL for
 	 * devices that do not have multiple independent access ranges.
-- 
2.34.1

On 9/14/25 4:45 AM, Wang Jianzheng wrote:
>   block/genhd.c          | 23 +++++++++++++++++++++++
>   include/linux/blkdev.h |  2 ++

If  a new sysfs attribute is added then an entry must be added in
Documentation/ABI/ that explains the purpose of the new attribute and
also how to use it.

> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -213,6 +213,8 @@ struct gendisk {
>   	u64 diskseq;
>   	blk_mode_t open_mode;
>   
> +	int dev_freq_timeout;

The name `dev_freq_timeout` is not sufficient to guess the meaning of
the attribute. Please add a comment.

Thanks,

Bart.