[PATCH v14 18/19] scsi: ufs: Forbid auto-hibernation without I/O scheduler

Bart Van Assche
2023-10-23T21:58:26Z

UFSHCI controllers in legacy mode do not preserve the write order if
auto-hibernation is enabled. If the write order is not preserved, an I/O
scheduler is required to serialize zoned writes. Hence do not allow
auto-hibernation to be enabled without I/O scheduler if a zoned logical unit
is present and if the controller is operating in legacy mode. This patch has
been tested with the following shell script:

show_ah8() {
echo -n "auto_hibern8: "
adb shell "cat /sys/devices/platform/13200000.ufs/auto_hibern8"
}

set_ah8() {
local rc
adb shell "echo $1 > /sys/devices/platform/13200000.ufs/auto_hibern8"
rc=$?
show_ah8
return $rc
}

set_iosched() {
adb shell "echo $1 >/sys/class/block/$zoned_bdev/queue/scheduler &&
echo -n 'I/O scheduler: ' &&
cat /sys/class/block/sde/queue/scheduler"
}

adb root
zoned_bdev=$(adb shell grep -lvw 0 /sys/class/block/sd*/queue/chunk_sectors |&
sed 's|/sys/class/block/||g;s|/queue/chunk_sectors||g')
[ -n "$zoned_bdev" ]
show_ah8
set_ah8 0
set_iosched none
if set_ah8 150000; then
echo "Error: enabled AH8 without I/O scheduler"
fi
set_iosched mq-deadline
set_ah8 150000

Reviewed-by: Bao D. Nguyen <quic_nguyenb@quicinc.com>
Reviewed-by: Can Guo <quic_cang@quicinc.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/ufs/core/ufshcd.c | 60 +++++++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 3fc33794ce1f..0a21ea9d7576 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -4305,6 +4305,30 @@ int ufshcd_uic_hibern8_exit(struct ufs_hba *hba)
}
EXPORT_SYMBOL_GPL(ufshcd_uic_hibern8_exit);

+static int ufshcd_update_preserves_write_order(struct ufs_hba *hba,
+ bool preserves_write_order)
+{
+ struct scsi_device *sdev;
+
+ if (!preserves_write_order) {
+ shost_for_each_device(sdev, hba->host) {
+ struct request_queue *q = sdev->request_queue;
+
+ /*
+ * Refuse to enable auto-hibernation if no I/O scheduler
+ * is present. This code does not check whether the
+ * attached I/O scheduler serializes zoned writes
+ * (ELEVATOR_F_ZBD_SEQ_WRITE) because this cannot be
+ * checked from outside the block layer core.
+ */
+ if (blk_queue_is_zoned(q) && !q->elevator)
+ return -EPERM;
+ }
+ }
+
+ return 0;
+}
+
static void ufshcd_configure_auto_hibern8(struct ufs_hba *hba)
{
if (!ufshcd_is_auto_hibern8_supported(hba))
@@ -4313,13 +4337,42 @@ static void ufshcd_configure_auto_hibern8(struct ufs_hba *hba)
ufshcd_writel(hba, hba->ahit, REG_AUTO_HIBERNATE_IDLE_TIMER);
}

+/**
+ * ufshcd_auto_hibern8_update() - Modify the auto-hibernation control register
+ * @hba: per-adapter instance
+ * @ahit: New auto-hibernate settings. Includes the scale and the value of the
+ * auto-hibernation timer. See also the UFSHCI_AHIBERN8_TIMER_MASK and
+ * UFSHCI_AHIBERN8_SCALE_MASK constants.
+ *
+ * Notes:
+ * - UFSHCI controllers do not preserve the command order in legacy mode
+ * if auto-hibernation is enabled. If the command order is not preserved, an
+ * I/O scheduler that serializes zoned writes (mq-deadline) is required if a
+ * zoned logical unit is present. Enabling auto-hibernation without attaching
+ * the mq-deadline scheduler first may cause unaligned write errors for the
+ * zoned logical unit if a zoned logical unit is present.
+ * - Calls of this function must be serialized.
+ */
int ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
{
const u32 cur_ahit = READ_ONCE(hba->ahit);
+ bool prev_state, new_state;
+ int ret;

if (!ufshcd_is_auto_hibern8_supported(hba) || cur_ahit == ahit)
return 0;

+ prev_state = FIELD_GET(UFSHCI_AHIBERN8_TIMER_MASK, cur_ahit);
+ new_state = FIELD_GET(UFSHCI_AHIBERN8_TIMER_MASK, ahit);
+
+ if (!is_mcq_enabled(hba) && !prev_state && new_state) {
+ /*
+ * Auto-hibernation will be enabled for legacy UFSHCI mode.
+ */
+ ret = ufshcd_update_preserves_write_order(hba, false);
+ if (ret)
+ return ret;
+ }
WRITE_ONCE(hba->ahit, ahit);
if (!pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev)) {
ufshcd_rpm_get_sync(hba);
@@ -4328,6 +4381,13 @@ int ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
ufshcd_release(hba);
ufshcd_rpm_put_sync(hba);
}
+ if (!is_mcq_enabled(hba) && prev_state && !new_state) {
+ /*
+ * Auto-hibernation has been disabled.
+ */
+ ret = ufshcd_update_preserves_write_order(hba, true);
+ WARN_ON_ONCE(ret);
+ }

return 0;
}