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Date: Wed, 13 Jan 2021 18:49:25 +0800
From: Can Guo <cang@...eaurora.org>
To: 황두현 <dh0421.hwang@...sung.com>
Cc: adrian.hunter@...el.com, alim.akhtar@...sung.com,
asutoshd@...eaurora.org, avri.altman@....com, beanhuo@...ron.com,
hongwus@...eaurora.org, jejb@...ux.ibm.com,
kernel-team@...roid.com, linux-kernel@...r.kernel.org,
linux-scsi@...r.kernel.org, martin.petersen@...cle.com,
nguyenb@...eaurora.org, rnayak@...eaurora.org, salyzyn@...gle.com,
saravanak@...gle.com, satyat@...gle.com, stanley.chu@...iatek.com,
grant.jung@...sung.com, jt77.jang@...sung.com,
junwoo80.lee@...sung.com, sh043.lee@...sung.com,
jangsub.yi@...sung.com, cw9316.lee@...sung.com,
sh8267.baek@...sung.com, wkon.kim@...sung.com
Subject: Re: [PATCH v9 1/3] scsi: ufs: Protect some contexts from unexpected
clock scaling
On 2021-01-13 18:14, 황두현 wrote:
>> From: Can Guo <cang@...eaurora.org>
>>
>> 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 devfreq sysfs nodes like
>> min/max_freq and
>> governor even after devfreq is suspended. Moreover, mere suspending
>> devfreq
>> cannot synchroinze a clock scaling which has already been invoked
>> through
>> these sysfs nodes. Add one more flag in struct clk_scaling and wrap
>> the
>> entire func ufshcd_devfreq_scale() with the clk_scaling_lock, so that
>> we
>> can use this flag and clk_scaling_lock to control and synchronize
>> clock
>> scaling invoked through devfreq sysfs nodes.
>>
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> ---
>> drivers/scsi/ufs/ufshcd.c | 86
>> +++++++++++++++++++++++++++++------------------
>> drivers/scsi/ufs/ufshcd.h | 6 +++-
>> 2 files changed, 59 insertions(+), 33 deletions(-)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 82ad317..64218e6 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -1181,19 +1181,33 @@ 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)) {
>> +
>
> I think another value is better than -EAGAIN.
> Ex) -EPERM because the clk scaling is not allowed state.
-EPERM is usually used by IOCTL to tell users that
they don't have right permissions. -EAGAIN here tells
the caller that if it tries again, it may success, i.e
after hba is runtime resumed or error recovery is completed.
>
>> + if (!hba->clk_scaling.is_allowed)
>> + ret = -EAGAIN;
>
> I think ufshcd_hold() has to be called before access host registers,
> so calling ufshcd_hold() is better before calling
> ufshcd_clock_scaling_prepare().
>
> If you want to do not anything when hba->clk_scaling.is_allowed is
> false,
> it is recommended to check hba->clk_scaling.is_allowed before calling
> ufshcd_hold() in ufshcd_devfreq_scale().
Check ufshcd_wait_for_doorbell_clr(), it calls ufshcd_hold/release()
inside.
>
>> + 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;
>> }
>>
>> -static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
>> +static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool
>> writelock)
>> {
>> - up_write(&hba->clk_scaling_lock);
>> + if (writelock)
>> + up_write(&hba->clk_scaling_lock);
>> + else
>> + up_read(&hba->clk_scaling_lock);
>> ufshcd_scsi_unblock_requests(hba);
>> + ufshcd_release(hba);
>> }
>>
>> /**
>> @@ -1208,13 +1222,11 @@ static void
>> ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
>> 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);
>> + bool is_writelock = true;
>>
>
> I think it would be nice to call ufshcd_hold() here.
No, if hba is runtime suspended (rpm_lvl = 3/4/5),
calling ufshcd_hold() here shall fail, because you
are trying to exit hibern8 even when UFS is not
powered or VCCQ2/VCCQ in LPM.
So ufshcd_hold MUST come after hba->clk_scaling.is_allowed
check in prepare(), and the code is clean and tight if
ufshcd_hold() is put in prepare().
>
>> ret = ufshcd_clock_scaling_prepare(hba);
>> if (ret)
>
> Below change is not needed if calling ufshcd_hold() is before calling
> ufshcd_clock_scaling_prepare().
>
See my comments above.
>> - goto out;
>> + return ret;
>>
>> /* scale down the gear before scaling down clocks */
>> if (!scale_up) {
>> @@ -1240,14 +1252,12 @@ static int ufshcd_devfreq_scale(struct ufs_hba
>> *hba, bool scale_up)
>> }
>>
>> /* Enable Write Booster if we have scaled up else disable it */
>> - up_write(&hba->clk_scaling_lock);
>> + downgrade_write(&hba->clk_scaling_lock);
>> + is_writelock = false;
>> ufshcd_wb_ctrl(hba, scale_up);
>> - down_write(&hba->clk_scaling_lock);
>>
>> out_unprepare:
>> - ufshcd_clock_scaling_unprepare(hba);
>> -out:
>> - ufshcd_release(hba);
>> + ufshcd_clock_scaling_unprepare(hba, is_writelock);
>> return ret;
>> }
>>
>> @@ -1521,7 +1531,7 @@ 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,
>> @@ -1535,7 +1545,7 @@ static ssize_t
>> ufshcd_clkscale_enable_store(struct device *dev,
>> return -EINVAL;
>>
>> value = !!value;
>> - if (value == hba->clk_scaling.is_allowed)
>> + if (value == hba->clk_scaling.is_enabled)
>> goto out;
>>
>> pm_runtime_get_sync(hba->dev);
>> @@ -1544,7 +1554,7 @@ 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;
>> + hba->clk_scaling.is_enabled = value;
>>
>> if (value) {
>> ufshcd_resume_clkscaling(hba);
>> @@ -1882,8 +1892,6 @@ 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)
>> @@ -1891,6 +1899,8 @@ static void ufshcd_exit_clk_scaling(struct
>> ufs_hba *hba)
>> if (!ufshcd_is_clkscaling_supported(hba))
>> return;
>>
>> + if (hba->clk_scaling.enable_attr.attr.name)
>> + device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
>> destroy_workqueue(hba->clk_scaling.workq);
>> ufshcd_devfreq_remove(hba);
>> }
>> @@ -1955,7 +1965,7 @@ 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)
>> @@ -5071,7 +5081,8 @@ static void __ufshcd_transfer_req_compl(struct
>> ufs_hba *hba,
>> update_scaling = true;
>> }
>> }
>> - if (ufshcd_is_clkscaling_supported(hba) && update_scaling)
>> + if (ufshcd_is_clkscaling_supported(hba) && update_scaling &&
>> + hba->clk_scaling.active_reqs > 0)
>> hba->clk_scaling.active_reqs--;
>> }
>>
>> @@ -5737,18 +5748,24 @@ static void ufshcd_err_handling_prepare(struct
>> ufs_hba *hba)
>> ufshcd_vops_resume(hba, pm_op);
>> } 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);
>> }
>> @@ -7728,12 +7745,14 @@ 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;
>> 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);
>> @@ -8650,11 +8669,14 @@ 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) {
>> @@ -8751,8 +8773,6 @@ 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);
>> /*
>> * Device hardware reset is required to exit DeepSleep. Also, for
>> @@ -8776,7 +8796,10 @@ 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;
>> @@ -8879,7 +8902,10 @@ 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 */
>> @@ -8903,8 +8929,6 @@ 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;
>> @@ -9131,8 +9155,6 @@ 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 aa9ea35..2863af1 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -419,7 +419,10 @@ struct ufs_saved_pwr_info {
>> * @suspend_work: worker to suspend devfreq
>> * @resume_work: worker to resume devfreq
>> * @min_gear: lowest HS gear to scale down to
>> - * @is_allowed: tracks if scaling is currently allowed or not
>> + * @is_enabled: tracks if scaling is currently enabled or not,
>> controlled by
>> + clkscale_enable sysfs node
>> + * @is_allowed: tracks if scaling is currently allowed or not, used
>> to block
>> + clock scaling which is not invoked from devfreq governor
>> * @is_busy_started: tracks if busy period has started or not
>> * @is_suspended: tracks if devfreq is suspended or not
>> */
>> @@ -434,6 +437,7 @@ struct ufs_clk_scaling {
>> struct work_struct suspend_work;
>> struct work_struct resume_work;
>> u32 min_gear;
>> + bool is_enabled;
>> bool is_allowed;
>> bool is_busy_started;
>> bool is_suspended;
>> --
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
>> Linux Foundation Collaborative Project.
>
> --
> DooHyun Hwang
> Samsung Electronics
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