Re: [PATCH v4 1/3] scsi: ufs: Protect some contexts from unexpected clock scaling

From: Can Guo
Date: Fri Dec 18 2020 - 01:27:15 EST

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On 2020-12-15 13:43, Stanley Chu wrote:

Hi Can,

On Sun, 2020-12-13 at 08:31 -0800, Can Guo wrote:

In contexts like suspend, shutdown and error handling, we need to suspend
devfreq to make sure these contexts won't be disturbed by clock scaling.
However, suspending devfreq is not enough since users can still trigger a
clock scaling by manipulating the sysfs node clkscale_enable and devfreq
sysfs nodes like min/max_freq and governor. Add one more flag in struct
clk_scaling such that these contexts can prevent clock scaling from being
invoked through above sysfs nodes.

Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
---
drivers/scsi/ufs/ufshcd.c | 83 +++++++++++++++++++++++++++++++----------------
drivers/scsi/ufs/ufshcd.h | 2 ++
2 files changed, 57 insertions(+), 28 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 0c148fc..4ccdd2b 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1147,12 +1147,22 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
*/
ufshcd_scsi_block_requests(hba);
down_write(&hba->clk_scaling_lock);
- if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
+
+ if (!hba->clk_scaling.is_allowed)
+ ret = -EAGAIN;
+ else if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US))
ret = -EBUSY;
+
+ if (ret) {
up_write(&hba->clk_scaling_lock);
ufshcd_scsi_unblock_requests(hba);
+ goto out;
}

+ /* let's not get into low power until clock scaling is completed */
+ ufshcd_hold(hba, false);
+
+out:
return ret;
}

@@ -1160,6 +1170,7 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
{
up_write(&hba->clk_scaling_lock);
ufshcd_scsi_unblock_requests(hba);
+ ufshcd_release(hba);
}

/**
@@ -1175,12 +1186,9 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
{
int ret = 0;

- /* let's not get into low power until clock scaling is completed */
- ufshcd_hold(hba, false);
-
ret = ufshcd_clock_scaling_prepare(hba);
if (ret)
- goto out;
+ return ret;

/* scale down the gear before scaling down clocks */
if (!scale_up) {
@@ -1212,8 +1220,6 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)

out_unprepare:
ufshcd_clock_scaling_unprepare(hba);
-out:
- ufshcd_release(hba);
return ret;
}

@@ -1487,7 +1493,7 @@ static ssize_t ufshcd_clkscale_enable_show(struct device *dev,
{
struct ufs_hba *hba = dev_get_drvdata(dev);

- return snprintf(buf, PAGE_SIZE, "%d\n", hba->clk_scaling.is_allowed);
+ return snprintf(buf, PAGE_SIZE, "%d\n", hba->clk_scaling.is_enabled);
}

static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
@@ -1496,12 +1502,20 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
struct ufs_hba *hba = dev_get_drvdata(dev);
u32 value;
int err;
+ unsigned long flags;
+ bool update = true;

if (kstrtou32(buf, 0, &value))
return -EINVAL;

value = !!value;
- if (value == hba->clk_scaling.is_allowed)
+ spin_lock_irqsave(hba->host->host_lock, flags);
+ if (value == hba->clk_scaling.is_enabled)
+ update = false;
+ else
+ hba->clk_scaling.is_enabled = value;
+ spin_unlock_irqrestore(hba->host->host_lock, flags);
+ if (!update)
goto out;

pm_runtime_get_sync(hba->dev);
@@ -1510,8 +1524,6 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
cancel_work_sync(&hba->clk_scaling.suspend_work);
cancel_work_sync(&hba->clk_scaling.resume_work);

- hba->clk_scaling.is_allowed = value;
-
if (value) {
ufshcd_resume_clkscaling(hba);
} else {
@@ -1845,8 +1857,6 @@ static void ufshcd_init_clk_scaling(struct ufs_hba *hba)
snprintf(wq_name, sizeof(wq_name), "ufs_clkscaling_%d",
hba->host->host_no);
hba->clk_scaling.workq = create_singlethread_workqueue(wq_name);
-
- ufshcd_clkscaling_init_sysfs(hba);
}

static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
@@ -1854,6 +1864,8 @@ static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
if (!ufshcd_is_clkscaling_supported(hba))
return;

+ if (hba->devfreq)
+ device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
destroy_workqueue(hba->clk_scaling.workq);
ufshcd_devfreq_remove(hba);
}
@@ -1918,7 +1930,7 @@ static void ufshcd_clk_scaling_start_busy(struct ufs_hba *hba)
if (!hba->clk_scaling.active_reqs++)
queue_resume_work = true;

- if (!hba->clk_scaling.is_allowed || hba->pm_op_in_progress)
+ if (!hba->clk_scaling.is_enabled || hba->pm_op_in_progress)
return;

if (queue_resume_work)
@@ -4987,7 +4999,8 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
complete(hba->dev_cmd.complete);
}
}
- if (ufshcd_is_clkscaling_supported(hba))
+ if (ufshcd_is_clkscaling_supported(hba) &&
+ hba->clk_scaling.active_reqs > 0)
hba->clk_scaling.active_reqs--;
}

@@ -5650,18 +5663,25 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
ufshcd_vops_resume(hba, UFS_RUNTIME_PM);
} else {
ufshcd_hold(hba, false);
- if (hba->clk_scaling.is_allowed) {
+ if (hba->clk_scaling.is_enabled) {
cancel_work_sync(&hba->clk_scaling.suspend_work);
cancel_work_sync(&hba->clk_scaling.resume_work);
ufshcd_suspend_clkscaling(hba);
}
}
+ down_write(&hba->clk_scaling_lock);
+ hba->clk_scaling.is_allowed = false;
+ up_write(&hba->clk_scaling_lock);
}

static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)
{
ufshcd_release(hba);
- if (hba->clk_scaling.is_allowed)
+
+ down_write(&hba->clk_scaling_lock);
+ hba->clk_scaling.is_allowed = true;
+ up_write(&hba->clk_scaling_lock);
+ if (hba->clk_scaling.is_enabled)
ufshcd_resume_clkscaling(hba);
pm_runtime_put(hba->dev);
}
@@ -7620,12 +7640,14 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
sizeof(struct ufs_pa_layer_attr));
hba->clk_scaling.saved_pwr_info.is_valid = true;
if (!hba->devfreq) {
+ hba->clk_scaling.is_allowed = true;

Perhaps moving this line after ufshcd_devfreq_init() is successful?

devfreq starts to work even before ufshcd_devfreq_init() returns,
I don't want to block it, hence put it before ufshcd_devfreq_init().
If devfreq fails to initialize, clk_scaling and its related sysfs
nodes anyways won't work and clk_scaling->is_enabled is false, so
we are safe.

ret = ufshcd_devfreq_init(hba);
if (ret)
goto out;
- }

- hba->clk_scaling.is_allowed = true;
+ hba->clk_scaling.is_enabled = true;
+ ufshcd_clkscaling_init_sysfs(hba);
+ }
}

ufs_bsg_probe(hba);
@@ -8491,11 +8513,14 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
ufshcd_hold(hba, false);
hba->clk_gating.is_suspended = true;

- if (hba->clk_scaling.is_allowed) {
+ if (hba->clk_scaling.is_enabled) {
cancel_work_sync(&hba->clk_scaling.suspend_work);
cancel_work_sync(&hba->clk_scaling.resume_work);
ufshcd_suspend_clkscaling(hba);
}
+ down_write(&hba->clk_scaling_lock);
+ hba->clk_scaling.is_allowed = false;
+ up_write(&hba->clk_scaling_lock);

if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
req_link_state == UIC_LINK_ACTIVE_STATE) {
@@ -8592,8 +8617,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
goto out;

set_link_active:
- if (hba->clk_scaling.is_allowed)
- ufshcd_resume_clkscaling(hba);
ufshcd_vreg_set_hpm(hba);
if (ufshcd_is_link_hibern8(hba) && !ufshcd_uic_hibern8_exit(hba))
ufshcd_set_link_active(hba);
@@ -8603,7 +8626,10 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
ufshcd_disable_auto_bkops(hba);
enable_gating:
- if (hba->clk_scaling.is_allowed)
+ down_write(&hba->clk_scaling_lock);
+ hba->clk_scaling.is_allowed = true;
+ up_write(&hba->clk_scaling_lock);
+ if (hba->clk_scaling.is_enabled)
ufshcd_resume_clkscaling(hba);
hba->clk_gating.is_suspended = false;
hba->dev_info.b_rpm_dev_flush_capable = false;
@@ -8701,7 +8727,10 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)

hba->clk_gating.is_suspended = false;

- if (hba->clk_scaling.is_allowed)
+ down_write(&hba->clk_scaling_lock);
+ hba->clk_scaling.is_allowed = true;
+ up_write(&hba->clk_scaling_lock);
+ if (hba->clk_scaling.is_enabled)
ufshcd_resume_clkscaling(hba);

/* Enable Auto-Hibernate if configured */
@@ -8725,8 +8754,6 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
ufshcd_vreg_set_lpm(hba);
disable_irq_and_vops_clks:
ufshcd_disable_irq(hba);
- if (hba->clk_scaling.is_allowed)
- ufshcd_suspend_clkscaling(hba);
ufshcd_setup_clocks(hba, false);
if (ufshcd_is_clkgating_allowed(hba)) {
hba->clk_gating.state = CLKS_OFF;
@@ -8915,6 +8942,8 @@ int ufshcd_shutdown(struct ufs_hba *hba)

pm_runtime_get_sync(hba->dev);

+ ufshcd_exit_clk_scaling(hba);
+
ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
out:
if (ret)
@@ -8944,8 +8973,6 @@ void ufshcd_remove(struct ufs_hba *hba)

ufshcd_exit_clk_scaling(hba);
ufshcd_exit_clk_gating(hba);
- if (ufshcd_is_clkscaling_supported(hba))
- device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
ufshcd_hba_exit(hba);
}
EXPORT_SYMBOL_GPL(ufshcd_remove);
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index e0f00a4..9fcecba 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -382,6 +382,7 @@ struct ufs_saved_pwr_info {
* @workq: workqueue to schedule devfreq suspend/resume work
* @suspend_work: worker to suspend devfreq
* @resume_work: worker to resume devfreq
+ * @is_enabled: tracks if scaling is currently enabled or not
* @is_allowed: tracks if scaling is currently allowed or not
* @is_busy_started: tracks if busy period has started or not
* @is_suspended: tracks if devfreq is suspended or not
@@ -396,6 +397,7 @@ struct ufs_clk_scaling {
struct workqueue_struct *workq;
struct work_struct suspend_work;
struct work_struct resume_work;
+ bool is_enabled;
bool is_allowed;
bool is_busy_started;
bool is_suspended;

Now there are more and more "similar boolean attributes" regarding
clk-scaling control, maybe add more comprehensive comments to describe
them?

Otherwise this patch looks good to me.

Sure, I will give more words to the new flag.

Thanks,

Can Guo.

Feel free to add
Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>

Next message: Jiri Slaby: "Re: drivers/tty/vt/keyboard.c:2037:13: sparse: sparse: incorrect type in initializer (different address spaces)"
Previous message: Lakshmi Ramasubramanian: "Re: [PATCH v12 2/4] powerpc: Move arch independent ima kexec functions to drivers/of/kexec.c"
In reply to: Bean Huo: "Re: [PATCH v4 1/3] scsi: ufs: Protect some contexts from unexpected clock scaling"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]