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Date: Fri, 18 Dec 2020 14:26:06 +0800
From: Can Guo <cang@...eaurora.org>
To: Stanley Chu <stanley.chu@...iatek.com>
Cc: asutoshd@...eaurora.org, nguyenb@...eaurora.org,
hongwus@...eaurora.org, rnayak@...eaurora.org,
linux-scsi@...r.kernel.org, kernel-team@...roid.com,
saravanak@...gle.com, salyzyn@...gle.com,
Alim Akhtar <alim.akhtar@...sung.com>,
Avri Altman <avri.altman@....com>,
"James E.J. Bottomley" <jejb@...ux.ibm.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Bean Huo <beanhuo@...ron.com>,
Bart Van Assche <bvanassche@....org>,
Satya Tangirala <satyat@...gle.com>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/3] scsi: ufs: Protect some contexts from unexpected
clock scaling
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@...eaurora.org>
>> ---
>> 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@...iatek.com>
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