Re: [PATCH v18 1/2] scsi: ufs: Enable power management for wlun

[Adrian Hunter]

On 14/04/21 9:58 pm, Asutosh Das wrote:
> During runtime-suspend of ufs host, the scsi devices are
> already suspended and so are the queues associated with them.
> But the ufs host sends SSU (START_STOP_UNIT) to wlun
> during its runtime-suspend.
> During the process blk_queue_enter checks if the queue is not in
> suspended state. If so, it waits for the queue to resume, and never
> comes out of it.
> The commit
> (d55d15a33: scsi: block: Do not accept any requests while suspended)
> adds the check if the queue is in suspended state in blk_queue_enter().
> 
> Call trace:
>  __switch_to+0x174/0x2c4
>  __schedule+0x478/0x764
>  schedule+0x9c/0xe0
>  blk_queue_enter+0x158/0x228
>  blk_mq_alloc_request+0x40/0xa4
>  blk_get_request+0x2c/0x70
>  __scsi_execute+0x60/0x1c4
>  ufshcd_set_dev_pwr_mode+0x124/0x1e4
>  ufshcd_suspend+0x208/0x83c
>  ufshcd_runtime_suspend+0x40/0x154
>  ufshcd_pltfrm_runtime_suspend+0x14/0x20
>  pm_generic_runtime_suspend+0x28/0x3c
>  __rpm_callback+0x80/0x2a4
>  rpm_suspend+0x308/0x614
>  rpm_idle+0x158/0x228
>  pm_runtime_work+0x84/0xac
>  process_one_work+0x1f0/0x470
>  worker_thread+0x26c/0x4c8
>  kthread+0x13c/0x320
>  ret_from_fork+0x10/0x18
> 
> Fix this by registering ufs device wlun as a scsi driver and
> registering it for block runtime-pm. Also make this as a
> supplier for all other luns. That way, this device wlun
> suspends after all the consumers and resumes after
> hba resumes.

Can you also explain the new driver for RPMB WLUN and UAC changes here?

And also mention that the driver will now always be runtime
resumed before system suspend.

> 
> Co-developed-by: Can Guo <cang@xxxxxxxxxxxxxx>
> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> ---

<SNIP>

> +static void ufshcd_setup_links(struct ufs_hba *hba, struct scsi_device *sdev)
> +{
> +	struct device_link *link;
> +
> +	/*
> +	 * device wlun is the supplier & rest of the luns are consumers
> +	 * This ensures that device wlun suspends after all other luns.
> +	 */
> +	if (hba->sdev_ufs_device) {
> +		link = device_link_add(&sdev->sdev_gendev,
> +				       &hba->sdev_ufs_device->sdev_gendev,
> +				       DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);

"|" could be surrounded by spaces i.e.
				       DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE);

> +		if (!link) {
> +			dev_err(&sdev->sdev_gendev, "Failed establishing link - %s\n",
> +				dev_name(&hba->sdev_ufs_device->sdev_gendev));
> +			return;
> +		}
> +		hba->luns_avail--;
> +		/* Ignore REPORT_LUN wlun probing */
> +		if (hba->luns_avail == 1) {
> +			ufshcd_rpm_put(hba);
> +			return;
> +		}
> +	} else {
> +		/* device wlun is probed */
> +		hba->luns_avail--;
> +	}
> +}

<SNIP>

> @@ -8916,42 +8906,214 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	if (hba->ee_usr_mask)
>  		ufshcd_write_ee_control(hba);
>  
> -	hba->clk_gating.is_suspended = false;
> -
> -	if (ufshcd_is_clkscaling_supported(hba))
> -		ufshcd_clk_scaling_suspend(hba, false);
> -
> -	/* Enable Auto-Hibernate if configured */
> -	ufshcd_auto_hibern8_enable(hba);
> +	if (hba->clk_scaling.is_allowed)
> +		ufshcd_resume_clkscaling(hba);

We don't use clks, regulators, clk gating, clk scaling, but the
original code looks more correct because hba->clk_scaling.is_allowed
will have been set to false by ufshcd_clk_scaling_suspend(hba, true)
in __ufshcd_wl_suspend().

<SNIP>

> +#ifdef CONFIG_PM_SLEEP
> +static int ufshcd_wl_suspend(struct device *dev)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	struct ufs_hba *hba;
> +	int ret;

For below:
	int ret = 0;

> +	ktime_t start = ktime_get();
> +
> +	hba = shost_priv(sdev->host);
> +	down(&hba->host_sem);

If we get here with dev runtime suspended, then skip
__ufshcd_wl_suspend() i.e.

	if (pm_runtime_suspended(dev))
		goto out;

> +	ret = __ufshcd_wl_suspend(hba, UFS_SYSTEM_PM);
> +	if (ret) {
> +		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__,  ret);
> +		up(&hba->host_sem);
> +	} else {
> +		hba->is_sys_suspended = true;
> +	}

out:
	if (!ret)
		hba->is_sys_suspended = true;

> +
> +	trace_ufshcd_wl_suspend(dev_name(dev), ret,
> +		ktime_to_us(ktime_sub(ktime_get(), start)),
> +		hba->curr_dev_pwr_mode, hba->uic_link_state);
> +
> +	return ret;
> +}

<SNIP>