[PATCH v2 0/3] scsi: libsas: handle linkrate change in sas_rediscover_dev

[PATCH v2 0/3] scsi: libsas: handle linkrate change in sas_rediscover_dev

[Xingui Yang]

When a device attached to an expander phy experiences a linkrate change
(e.g., due to cable reconnection or negotiation), the current code in
sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
if the SAS address and device type remain unchanged.

However, for drivers like hisi_sas, the ITCT entry needs to be updated
to reflect the new linkrate. Without this update, the hardware continues
using stale linkrate information, which can cause performance issues or
protocol errors.

This series introduces a new LLDD callback lldd_dev_info_update() to
notify the low-level driver when a device's information changes, allowing
the driver to update its hardware structures accordingly. The callback
is designed to be extensible for future device information updates beyond
linkrate changes.

Changes from v1:
- Split into three patches.

Xingui Yang (3):
  scsi: libsas: refactor sas_ex_to_ata() using new helper
    sas_ex_to_dev()
  scsi: libsas: add lldd_dev_info_update callback for device info
    changes
  scsi: hisi_sas: add support for dev info update notification

 drivers/scsi/hisi_sas/hisi_sas_main.c | 16 ++++++++++++++++
 drivers/scsi/libsas/sas_discover.c    | 12 ++++++++++++
 drivers/scsi/libsas/sas_expander.c    | 25 +++++++++++++++++++------
 drivers/scsi/libsas/sas_internal.h    |  2 ++
 include/scsi/libsas.h                 |  1 +
 5 files changed, 50 insertions(+), 6 deletions(-)

-- 
2.43.0

[PATCH v2 1/3] scsi: libsas: refactor sas_ex_to_ata() using new helper sas_ex_to_dev()

[Xingui Yang]

The sas_ex_to_ata() function checks for an attached ATA device on an
expander phy. Refactor it to use a new helper function sas_ex_to_dev()
which returns any device type attached to an expander phy, improving code
reuse and allowing other code paths to find attached devices regardless
of type.

No functional changes intended.

Signed-off-by: Xingui Yang <yangxingui@huawei.com>
---
 drivers/scsi/libsas/sas_expander.c | 12 ++++++++----
 drivers/scsi/libsas/sas_internal.h |  1 +
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index f471ab464a78..f55ae9a979cd 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -345,11 +345,9 @@ static void sas_set_ex_phy(struct domain_device *dev, int phy_id,
 		 SAS_ADDR(phy->attached_sas_addr), type);
 }
 
-/* check if we have an existing attached ata device on this expander phy */
-struct domain_device *sas_ex_to_ata(struct domain_device *ex_dev, int phy_id)
+struct domain_device *sas_ex_to_dev(struct domain_device *ex_dev, int phy_id)
 {
 	struct ex_phy *ex_phy = &ex_dev->ex_dev.ex_phy[phy_id];
-	struct domain_device *dev;
 	struct sas_rphy *rphy;
 
 	if (!ex_phy->port)
@@ -359,7 +357,13 @@ struct domain_device *sas_ex_to_ata(struct domain_device *ex_dev, int phy_id)
 	if (!rphy)
 		return NULL;
 
-	dev = sas_find_dev_by_rphy(rphy);
+	return sas_find_dev_by_rphy(rphy);
+}
+
+/* check if we have an existing attached ata device on this expander phy */
+struct domain_device *sas_ex_to_ata(struct domain_device *ex_dev, int phy_id)
+{
+	struct domain_device *dev = sas_ex_to_dev(ex_dev, phy_id);
 
 	if (dev && dev_is_sata(dev))
 		return dev;
diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
index 7dce0f587149..350a70484bde 100644
--- a/drivers/scsi/libsas/sas_internal.h
+++ b/drivers/scsi/libsas/sas_internal.h
@@ -91,6 +91,7 @@ int sas_smp_get_phy_events(struct sas_phy *phy);
 
 void sas_device_set_phy(struct domain_device *dev, struct sas_port *port);
 struct domain_device *sas_find_dev_by_rphy(struct sas_rphy *rphy);
+struct domain_device *sas_ex_to_dev(struct domain_device *ex_dev, int phy_id);
 struct domain_device *sas_ex_to_ata(struct domain_device *ex_dev, int phy_id);
 int sas_ex_phy_discover(struct domain_device *dev, int single);
 int sas_get_report_phy_sata(struct domain_device *dev, int phy_id,
-- 
2.43.0

Re: [PATCH v2 1/3] scsi: libsas: refactor sas_ex_to_ata() using new helper sas_ex_to_dev()

[Jason Yan]

在 2026/5/13 10:16, Xingui Yang 写道:
> The sas_ex_to_ata() function checks for an attached ATA device on an
> expander phy. Refactor it to use a new helper function sas_ex_to_dev()
> which returns any device type attached to an expander phy, improving code
> reuse and allowing other code paths to find attached devices regardless
> of type.
> 
> No functional changes intended.
> 
> Signed-off-by: Xingui Yang<yangxingui@huawei.com>
> ---
>   drivers/scsi/libsas/sas_expander.c | 12 ++++++++----
>   drivers/scsi/libsas/sas_internal.h |  1 +
>   2 files changed, 9 insertions(+), 4 deletions(-)

Reviewed-by: Jason Yan <yanaijie@huawei.com>

[PATCH v2 2/3] scsi: libsas: add lldd_dev_info_update callback for device info changes

[Xingui Yang]

When a device attached to an expander phy experiences a linkrate change
(e.g., due to cable reconnection or negotiation), the current code in
sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
if the SAS address and device type remain unchanged.

However, for drivers like hisi_sas, the ITCT entry needs to be updated
to reflect the new linkrate. Without this update, the hardware continues
using stale linkrate information, which can cause performance issues or
protocol errors.

Introduce a new LLDD callback lldd_dev_info_update() to notify the
low-level driver when a device's information changes (such as linkrate),
allowing the driver to update its hardware structures accordingly. This
callback is designed to be extensible for future device information
updates.

Signed-off-by: Xingui Yang <yangxingui@huawei.com>
---
 drivers/scsi/libsas/sas_discover.c | 12 ++++++++++++
 drivers/scsi/libsas/sas_expander.c | 13 +++++++++++--
 drivers/scsi/libsas/sas_internal.h |  1 +
 include/scsi/libsas.h              |  1 +
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index b07062db50b2..60be59c45508 100644
--- a/drivers/scsi/libsas/sas_discover.c
+++ b/drivers/scsi/libsas/sas_discover.c
@@ -204,6 +204,18 @@ void sas_notify_lldd_dev_gone(struct domain_device *dev)
 	}
 }
 
+void sas_notify_lldd_dev_info_update(struct domain_device *dev)
+{
+	struct sas_ha_struct *sas_ha = dev->port->ha;
+	struct Scsi_Host *shost = sas_ha->shost;
+	struct sas_internal *i = to_sas_internal(shost->transportt);
+
+	if (!i->dft->lldd_dev_info_update)
+		return;
+
+	i->dft->lldd_dev_info_update(dev);
+}
+
 static void sas_probe_devices(struct asd_sas_port *port)
 {
 	struct domain_device *dev, *n;
diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index f55ae9a979cd..11165ba585b2 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -2017,13 +2017,22 @@ static int sas_rediscover_dev(struct domain_device *dev, int phy_id,
 		goto out_free_resp;
 	} else if (SAS_ADDR(sas_addr) == SAS_ADDR(phy->attached_sas_addr) &&
 		   dev_type_flutter(type, phy->attached_dev_type)) {
-		struct domain_device *ata_dev = sas_ex_to_ata(dev, phy_id);
+		struct domain_device *child_dev = sas_ex_to_dev(dev, phy_id);
 		char *action = "";
 
 		sas_ex_phy_discover(dev, phy_id);
 
-		if (ata_dev && phy->attached_dev_type == SAS_SATA_PENDING)
+		if (child_dev && dev_is_sata(child_dev) &&
+		    phy->attached_dev_type == SAS_SATA_PENDING) {
 			action = ", needs recovery";
+		} else if (child_dev && child_dev->linkrate != phy->linkrate) {
+			pr_debug("ex %016llx phy%02d linkrate changed: %d -> %d\n",
+				 SAS_ADDR(dev->sas_addr), phy_id,
+				 child_dev->linkrate, phy->linkrate);
+			child_dev->linkrate = phy->linkrate;
+			sas_notify_lldd_dev_info_update(child_dev);
+		}
+
 		pr_debug("ex %016llx phy%02d broadcast flutter%s\n",
 			 SAS_ADDR(dev->sas_addr), phy_id, action);
 		goto out_free_resp;
diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
index 350a70484bde..9ee37b8abd78 100644
--- a/drivers/scsi/libsas/sas_internal.h
+++ b/drivers/scsi/libsas/sas_internal.h
@@ -82,6 +82,7 @@ bool sas_queue_work(struct sas_ha_struct *ha, struct sas_work *sw);
 
 int sas_notify_lldd_dev_found(struct domain_device *);
 void sas_notify_lldd_dev_gone(struct domain_device *);
+void sas_notify_lldd_dev_info_update(struct domain_device *dev);
 
 void sas_smp_handler(struct bsg_job *job, struct Scsi_Host *shost,
 		struct sas_rphy *rphy);
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 163f23c92b41..973b4445b7e0 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -674,6 +674,7 @@ struct sas_domain_function_template {
 	/* GPIO support */
 	int (*lldd_write_gpio)(struct sas_ha_struct *, u8 reg_type,
 			       u8 reg_index, u8 reg_count, u8 *write_data);
+	void (*lldd_dev_info_update)(struct domain_device *dev);
 };
 
 extern int sas_register_ha(struct sas_ha_struct *);
-- 
2.43.0

Re: [PATCH v2 2/3] scsi: libsas: add lldd_dev_info_update callback for device info changes

[Jason Yan]

在 2026/5/13 10:16, Xingui Yang 写道:
> When a device attached to an expander phy experiences a linkrate change
> (e.g., due to cable reconnection or negotiation), the current code in
> sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
> if the SAS address and device type remain unchanged.
> 
> However, for drivers like hisi_sas, the ITCT entry needs to be updated
> to reflect the new linkrate. Without this update, the hardware continues
> using stale linkrate information, which can cause performance issues or
> protocol errors.
> 
> Introduce a new LLDD callback lldd_dev_info_update() to notify the
> low-level driver when a device's information changes (such as linkrate),
> allowing the driver to update its hardware structures accordingly. This
> callback is designed to be extensible for future device information
> updates.
> 
> Signed-off-by: Xingui Yang<yangxingui@huawei.com>
> ---
>   drivers/scsi/libsas/sas_discover.c | 12 ++++++++++++
>   drivers/scsi/libsas/sas_expander.c | 13 +++++++++++--
>   drivers/scsi/libsas/sas_internal.h |  1 +
>   include/scsi/libsas.h              |  1 +
>   4 files changed, 25 insertions(+), 2 deletions(-)

Reviewed-by: Jason Yan <yanaijie@huawei.com>

[PATCH v2 3/3] scsi: hisi_sas: add support for dev info update notification

[Xingui Yang]

Implement the lldd_dev_info_update callback for hisi_sas driver. When
a device's information changes (such as linkrate), clear the old ITCT
entry and setup a new one to reflect the new settings. This ensures the
hardware uses the correct information after events like cable reconnection
or renegotiation.

Signed-off-by: Xingui Yang <yangxingui@huawei.com>
---
 drivers/scsi/hisi_sas/hisi_sas_main.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index 944ce19ae2fc..095960aef6d8 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -900,6 +900,21 @@ static int hisi_sas_dev_found(struct domain_device *device)
 	return rc;
 }
 
+static void hisi_sas_dev_info_update(struct domain_device *device)
+{
+	struct hisi_hba *hisi_hba = dev_to_hisi_hba(device);
+	struct hisi_sas_device *sas_dev = device->lldd_dev;
+	struct device *dev = hisi_hba->dev;
+
+	if (!sas_dev)
+		return;
+
+	dev_info(dev, "update itct for device %016llx\n",
+		 SAS_ADDR(device->sas_addr));
+	hisi_hba->hw->clear_itct(hisi_hba, sas_dev);
+	hisi_hba->hw->setup_itct(hisi_hba, sas_dev);
+}
+
 int hisi_sas_sdev_configure(struct scsi_device *sdev, struct queue_limits *lim)
 {
 	struct domain_device *dev = sdev_to_domain_dev(sdev);
@@ -2168,6 +2183,7 @@ EXPORT_SYMBOL_GPL(hisi_sas_stt);
 static struct sas_domain_function_template hisi_sas_transport_ops = {
 	.lldd_dev_found		= hisi_sas_dev_found,
 	.lldd_dev_gone		= hisi_sas_dev_gone,
+	.lldd_dev_info_update	= hisi_sas_dev_info_update,
 	.lldd_execute_task	= hisi_sas_queue_command,
 	.lldd_control_phy	= hisi_sas_control_phy,
 	.lldd_abort_task	= hisi_sas_abort_task,
-- 
2.43.0

Re: [PATCH v2 3/3] scsi: hisi_sas: add support for dev info update notification

[Jason Yan]

在 2026/5/13 10:16, Xingui Yang 写道:
> Implement the lldd_dev_info_update callback for hisi_sas driver. When
> a device's information changes (such as linkrate), clear the old ITCT
> entry and setup a new one to reflect the new settings. This ensures the
> hardware uses the correct information after events like cable reconnection
> or renegotiation.
> 
> Signed-off-by: Xingui Yang<yangxingui@huawei.com>
> ---
>   drivers/scsi/hisi_sas/hisi_sas_main.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)

Reviewed-by: Jason Yan <yanaijie@huawei.com>

Re: [PATCH v2 0/3] scsi: libsas: handle linkrate change in sas_rediscover_dev

[John Garry]

On 13/05/2026 03:16, Xingui Yang wrote:
> When a device attached to an expander phy experiences a linkrate change
> (e.g., due to cable reconnection or negotiation), the current code in
> sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
> if the SAS address and device type remain unchanged.

Can sas_rediscover_dev() check the linkrate (vs expected) to understand 
that this flutter has renegotiated the linkrate and then consider it not 
just a flutter?

> 
> However, for drivers like hisi_sas, the ITCT entry needs to be updated
> to reflect the new linkrate. Without this update, the hardware continues
> using stale linkrate information, which can cause performance issues or
> protocol errors.
> 
> This series introduces a new LLDD callback lldd_dev_info_update() to
> notify the low-level driver when a device's information changes, allowing
> the driver to update its hardware structures accordingly. The callback
> is designed to be extensible for future device information updates beyond
> linkrate changes.
> 
> Changes from v1:
> - Split into three patches.
> 
> Xingui Yang (3):
>    scsi: libsas: refactor sas_ex_to_ata() using new helper
>      sas_ex_to_dev()
>    scsi: libsas: add lldd_dev_info_update callback for device info
>      changes
>    scsi: hisi_sas: add support for dev info update notification
> 
>   drivers/scsi/hisi_sas/hisi_sas_main.c | 16 ++++++++++++++++
>   drivers/scsi/libsas/sas_discover.c    | 12 ++++++++++++
>   drivers/scsi/libsas/sas_expander.c    | 25 +++++++++++++++++++------
>   drivers/scsi/libsas/sas_internal.h    |  2 ++
>   include/scsi/libsas.h                 |  1 +
>   5 files changed, 50 insertions(+), 6 deletions(-)
> 

Re: [PATCH v2 0/3] scsi: libsas: handle linkrate change in sas_rediscover_dev

[yangxingui]

On 2026/5/13 15:29, John Garry wrote:
> On 13/05/2026 03:16, Xingui Yang wrote:
>> When a device attached to an expander phy experiences a linkrate change
>> (e.g., due to cable reconnection or negotiation), the current code in
>> sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
>> if the SAS address and device type remain unchanged.
> 
> Can sas_rediscover_dev() check the linkrate (vs expected) to understand 
> that this flutter has renegotiated the linkrate and then consider it not 
> just a flutter?

Hi, John
Theoretically, it is possible. As early as 2019, Jason attempted to 
propose the solution you mentioned. He conducted a relatively 
comprehensive assessment for flutter, including scenarios where the SAS 
address changes or the ATA ID changes. However, in actual use, such 
situations almost never occur unless there is an extremely short time 
window during which the drive is swapped or a new SATA drive is 
replaced. Because this solution is associated with other modifications 
and may have significant impacts, it has not been adopted.

https://lore.kernel.org/linux-scsi/20190130082412.9357-6-yanaijie@huawei.com/

Currently, scenarios involving changes in linkrate are relatively more 
common, and such situations can be easily reproduced by manually 
adjusting the linkrate by sysfs. Therefore, a less impactful synchronous 
update solution was adopted.

Thanks.
Xingui