Regression on linux-next (next-20250708)

[Damien Le Moal]

On 7/25/25 3:43 PM, Borah, Chaitanya Kumar wrote:
> For some context in our kms_pm_rpm tests, we enable min_power policy for SATA
> so that we can reach deep runtime power states and restore the original policy
> after finishing. [5][6]
> 
> IIUC, the above change is based on spec and not something which can be
> reverted. So as I see it, we have to drop this code path for external ports.
> However I am not sure if we can achieve deep power states without enforcing it
> through the sysfs entry.
> 
> Atleast for the basic-rte subtest, the test passes if we comment out the
> functions controlling the SATA ports. We will need more testing to determine if
> this approach work. Any thoughts on it?
> 
> Also, are there other ways to detect a port is external other than receiving
> EOPNOTSUPP on the sysfs write?

The attached patch adds the "link_power_management_supported" sysfs device
attribute for drives connected to AHCI. Would that work for you ?

diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index 229429ba5027..495fa096dd65 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -1089,6 +1089,7 @@ static struct ata_port_operations ich_pata_ops = {
 };

 static struct attribute *piix_sidpr_shost_attrs[] = {
+       &dev_attr_link_power_management_supported.attr,
        &dev_attr_link_power_management_policy.attr,
        NULL
 };
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index b335fb7e5cb4..c79abdfcd7a9 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -111,6 +111,7 @@ static DEVICE_ATTR(em_buffer, S_IWUSR | S_IRUGO,
 static DEVICE_ATTR(em_message_supported, S_IRUGO, ahci_show_em_supported, NULL);

 static struct attribute *ahci_shost_attrs[] = {
+       &dev_attr_link_power_management_supported.attr,
        &dev_attr_link_power_management_policy.attr,
        &dev_attr_em_message_type.attr,
        &dev_attr_em_message.attr,
diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
index 0708686ca58a..82a1a72e47bf 100644
--- a/drivers/ata/libata-sata.c
+++ b/drivers/ata/libata-sata.c
@@ -900,6 +900,18 @@ static const char *ata_lpm_policy_names[] = {
        [ATA_LPM_MIN_POWER]             = "min_power",
 };

+static ssize_t ata_scsi_lpm_supported_show(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+       struct Scsi_Host *shost = class_to_shost(dev);
+       struct ata_port *ap = ata_shost_to_port(shost);
+
+       return sysfs_emit(buf, "%d\n", !(ap->flags & ATA_FLAG_NO_LPM));
+}
+DEVICE_ATTR(link_power_management_supported, S_IRUGO,
+           ata_scsi_lpm_supported_show, NULL);
+EXPORT_SYMBOL_GPL(dev_attr_link_power_management_supported);
+
 static ssize_t ata_scsi_lpm_store(struct device *device,
                                  struct device_attribute *attr,
                                  const char *buf, size_t count)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 1c0580627dbb..e9a6f37bd7f9 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -547,6 +547,7 @@ typedef void (*ata_postreset_fn_t)(struct ata_link *link,
unsigned int *classes)

 extern struct device_attribute dev_attr_unload_heads;
 #ifdef CONFIG_SATA_HOST
+extern struct device_attribute dev_attr_link_power_management_supported;
 extern struct device_attribute dev_attr_link_power_management_policy;
 extern struct device_attribute dev_attr_ncq_prio_supported;
 extern struct device_attribute dev_attr_ncq_prio_enable;


-- 
Damien Le Moal
Western Digital Research
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