Re: [PATCH v3 4/4] scsi: ufs: Ungate the clock synchronously

[Adrian Hunter <adrian.hunter@intel.com>]

On 26/05/23 20:29, Bart Van Assche wrote:
> Ungating the clock asynchronously causes ufshcd_queuecommand() to return
> SCSI_MLQUEUE_HOST_BUSY and hence causes commands to be requeued.  This is
> suboptimal. Allow ufshcd_queuecommand() to sleep such that clock ungating
> does not trigger command requeuing. Remove the ufshcd_scsi_block_requests()
> and ufshcd_scsi_unblock_requests() calls because these are no longer
> needed. The flush_work(&hba->clk_gating.ungate_work) call is sufficient to
> make the SCSI core wait for clock ungating to complete.
> 
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>

One minor comment below, and we don't use clock gating but it looks
OK to me, so neverthless:

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
>  drivers/ufs/core/ufs-sysfs.c     |  2 +-
>  drivers/ufs/core/ufshcd-crypto.c |  2 +-
>  drivers/ufs/core/ufshcd-priv.h   |  2 +-
>  drivers/ufs/core/ufshcd.c        | 84 ++++++++++----------------------
>  include/ufs/ufshcd.h             |  2 +-
>  5 files changed, 30 insertions(+), 62 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufs-sysfs.c b/drivers/ufs/core/ufs-sysfs.c
> index 883f0e44b54e..cdf3d5f2b77b 100644
> --- a/drivers/ufs/core/ufs-sysfs.c
> +++ b/drivers/ufs/core/ufs-sysfs.c
> @@ -168,7 +168,7 @@ static ssize_t auto_hibern8_show(struct device *dev,
>  	}
>  
>  	pm_runtime_get_sync(hba->dev);
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	ahit = ufshcd_readl(hba, REG_AUTO_HIBERNATE_IDLE_TIMER);
>  	ufshcd_release(hba);
>  	pm_runtime_put_sync(hba->dev);
> diff --git a/drivers/ufs/core/ufshcd-crypto.c b/drivers/ufs/core/ufshcd-crypto.c
> index 198360fe5e8e..f2c4422cab86 100644
> --- a/drivers/ufs/core/ufshcd-crypto.c
> +++ b/drivers/ufs/core/ufshcd-crypto.c
> @@ -24,7 +24,7 @@ static int ufshcd_program_key(struct ufs_hba *hba,
>  	u32 slot_offset = hba->crypto_cfg_register + slot * sizeof(*cfg);
>  	int err = 0;
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  
>  	if (hba->vops && hba->vops->program_key) {
>  		err = hba->vops->program_key(hba, cfg, slot);
> diff --git a/drivers/ufs/core/ufshcd-priv.h b/drivers/ufs/core/ufshcd-priv.h
> index d53b93c21a0c..22cac71090ae 100644
> --- a/drivers/ufs/core/ufshcd-priv.h
> +++ b/drivers/ufs/core/ufshcd-priv.h
> @@ -84,7 +84,7 @@ unsigned long ufshcd_mcq_poll_cqe_lock(struct ufs_hba *hba,
>  int ufshcd_read_string_desc(struct ufs_hba *hba, u8 desc_index,
>  			    u8 **buf, bool ascii);
>  
> -int ufshcd_hold(struct ufs_hba *hba, bool async);
> +void ufshcd_hold(struct ufs_hba *hba);
>  void ufshcd_release(struct ufs_hba *hba);

Declarations of ufshcd_hold() / ufshcd_release() seem to be
unnecessarily duplicated in drivers/ufs/core/ufshcd-priv.h
and include/ufs/ufshcd.h

>  
>  int ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd);
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index c2d9109102f3..2af4289a3bf5 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1189,7 +1189,7 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
>  	bool timeout = false, do_last_check = false;
>  	ktime_t start;
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	spin_lock_irqsave(hba->host->host_lock, flags);
>  	/*
>  	 * Wait for all the outstanding tasks/transfer requests.
> @@ -1310,7 +1310,7 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba, u64 timeout_us)
>  	}
>  
>  	/* let's not get into low power until clock scaling is completed */
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  
>  out:
>  	return ret;
> @@ -1640,7 +1640,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>  		goto out;
>  
>  	ufshcd_rpm_get_sync(hba);
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  
>  	hba->clk_scaling.is_enabled = value;
>  
> @@ -1723,7 +1723,7 @@ static void ufshcd_ungate_work(struct work_struct *work)
>  	spin_lock_irqsave(hba->host->host_lock, flags);
>  	if (hba->clk_gating.state == CLKS_ON) {
>  		spin_unlock_irqrestore(hba->host->host_lock, flags);
> -		goto unblock_reqs;
> +		return;
>  	}
>  
>  	spin_unlock_irqrestore(hba->host->host_lock, flags);
> @@ -1746,25 +1746,21 @@ static void ufshcd_ungate_work(struct work_struct *work)
>  		}
>  		hba->clk_gating.is_suspended = false;
>  	}
> -unblock_reqs:
> -	ufshcd_scsi_unblock_requests(hba);
>  }
>  
>  /**
>   * ufshcd_hold - Enable clocks that were gated earlier due to ufshcd_release.
>   * Also, exit from hibern8 mode and set the link as active.
>   * @hba: per adapter instance
> - * @async: This indicates whether caller should ungate clocks asynchronously.
>   */
> -int ufshcd_hold(struct ufs_hba *hba, bool async)
> +void ufshcd_hold(struct ufs_hba *hba)
>  {
> -	int rc = 0;
>  	bool flush_result;
>  	unsigned long flags;
>  
>  	if (!ufshcd_is_clkgating_allowed(hba) ||
>  	    !hba->clk_gating.is_initialized)
> -		goto out;
> +		return;
>  	spin_lock_irqsave(hba->host->host_lock, flags);
>  	hba->clk_gating.active_reqs++;
>  
> @@ -1781,15 +1777,10 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
>  		 */
>  		if (ufshcd_can_hibern8_during_gating(hba) &&
>  		    ufshcd_is_link_hibern8(hba)) {
> -			if (async) {
> -				rc = -EAGAIN;
> -				hba->clk_gating.active_reqs--;
> -				break;
> -			}
>  			spin_unlock_irqrestore(hba->host->host_lock, flags);
>  			flush_result = flush_work(&hba->clk_gating.ungate_work);
>  			if (hba->clk_gating.is_suspended && !flush_result)
> -				goto out;
> +				return;
>  			spin_lock_irqsave(hba->host->host_lock, flags);
>  			goto start;
>  		}
> @@ -1811,21 +1802,14 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
>  		hba->clk_gating.state = REQ_CLKS_ON;
>  		trace_ufshcd_clk_gating(dev_name(hba->dev),
>  					hba->clk_gating.state);
> -		if (queue_work(hba->clk_gating.clk_gating_workq,
> -			       &hba->clk_gating.ungate_work))
> -			ufshcd_scsi_block_requests(hba);
> +		queue_work(hba->clk_gating.clk_gating_workq,
> +			   &hba->clk_gating.ungate_work);
>  		/*
>  		 * fall through to check if we should wait for this
>  		 * work to be done or not.
>  		 */
>  		fallthrough;
>  	case REQ_CLKS_ON:
> -		if (async) {
> -			rc = -EAGAIN;
> -			hba->clk_gating.active_reqs--;
> -			break;
> -		}
> -
>  		spin_unlock_irqrestore(hba->host->host_lock, flags);
>  		flush_work(&hba->clk_gating.ungate_work);
>  		/* Make sure state is CLKS_ON before returning */
> @@ -1837,8 +1821,6 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
>  		break;
>  	}
>  	spin_unlock_irqrestore(hba->host->host_lock, flags);
> -out:
> -	return rc;
>  }
>  EXPORT_SYMBOL_GPL(ufshcd_hold);
>  
> @@ -2070,7 +2052,7 @@ static void ufshcd_exit_clk_gating(struct ufs_hba *hba)
>  	ufshcd_remove_clk_gating_sysfs(hba);
>  
>  	/* Ungate the clock if necessary. */
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	hba->clk_gating.is_initialized = false;
>  	ufshcd_release(hba);
>  
> @@ -2468,7 +2450,7 @@ int ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd)
>  	if (hba->quirks & UFSHCD_QUIRK_BROKEN_UIC_CMD)
>  		return 0;
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	mutex_lock(&hba->uic_cmd_mutex);
>  	ufshcd_add_delay_before_dme_cmd(hba);
>  
> @@ -2871,12 +2853,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
>  
>  	WARN_ONCE(tag < 0 || tag >= hba->nutrs, "Invalid tag %d\n", tag);
>  
> -	/*
> -	 * Allows the UFS error handler to wait for prior ufshcd_queuecommand()
> -	 * calls.
> -	 */
> -	rcu_read_lock();
> -
>  	switch (hba->ufshcd_state) {
>  	case UFSHCD_STATE_OPERATIONAL:
>  		break;
> @@ -2922,13 +2898,7 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
>  
>  	hba->req_abort_count = 0;
>  
> -	err = ufshcd_hold(hba, true);
> -	if (err) {
> -		err = SCSI_MLQUEUE_HOST_BUSY;
> -		goto out;
> -	}
> -	WARN_ON(ufshcd_is_clkgating_allowed(hba) &&
> -		(hba->clk_gating.state != CLKS_ON));
> +	ufshcd_hold(hba);
>  
>  	lrbp = &hba->lrb[tag];
>  	lrbp->cmd = cmd;
> @@ -2956,8 +2926,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
>  	ufshcd_send_command(hba, tag, hwq);
>  
>  out:
> -	rcu_read_unlock();
> -
>  	if (ufs_trigger_eh()) {
>  		unsigned long flags;
>  
> @@ -3251,7 +3219,7 @@ int ufshcd_query_flag(struct ufs_hba *hba, enum query_opcode opcode,
>  
>  	BUG_ON(!hba);
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	mutex_lock(&hba->dev_cmd.lock);
>  	ufshcd_init_query(hba, &request, &response, opcode, idn, index,
>  			selector);
> @@ -3325,7 +3293,7 @@ int ufshcd_query_attr(struct ufs_hba *hba, enum query_opcode opcode,
>  		return -EINVAL;
>  	}
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  
>  	mutex_lock(&hba->dev_cmd.lock);
>  	ufshcd_init_query(hba, &request, &response, opcode, idn, index,
> @@ -3421,7 +3389,7 @@ static int __ufshcd_query_descriptor(struct ufs_hba *hba,
>  		return -EINVAL;
>  	}
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  
>  	mutex_lock(&hba->dev_cmd.lock);
>  	ufshcd_init_query(hba, &request, &response, opcode, idn, index,
> @@ -4239,7 +4207,7 @@ int ufshcd_uic_change_pwr_mode(struct ufs_hba *hba, u8 mode)
>  	uic_cmd.command = UIC_CMD_DME_SET;
>  	uic_cmd.argument1 = UIC_ARG_MIB(PA_PWRMODE);
>  	uic_cmd.argument3 = mode;
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	ret = ufshcd_uic_pwr_ctrl(hba, &uic_cmd);
>  	ufshcd_release(hba);
>  
> @@ -4346,7 +4314,7 @@ void ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
>  	if (update &&
>  	    !pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev)) {
>  		ufshcd_rpm_get_sync(hba);
> -		ufshcd_hold(hba, false);
> +		ufshcd_hold(hba);
>  		ufshcd_auto_hibern8_enable(hba);
>  		ufshcd_release(hba);
>  		ufshcd_rpm_put_sync(hba);
> @@ -4939,7 +4907,7 @@ static int ufshcd_verify_dev_init(struct ufs_hba *hba)
>  	int err = 0;
>  	int retries;
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	mutex_lock(&hba->dev_cmd.lock);
>  	for (retries = NOP_OUT_RETRIES; retries > 0; retries--) {
>  		err = ufshcd_exec_dev_cmd(hba, DEV_CMD_TYPE_NOP,
> @@ -6224,14 +6192,14 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
>  		ufshcd_setup_vreg(hba, true);
>  		ufshcd_config_vreg_hpm(hba, hba->vreg_info.vccq);
>  		ufshcd_config_vreg_hpm(hba, hba->vreg_info.vccq2);
> -		ufshcd_hold(hba, false);
> +		ufshcd_hold(hba);
>  		if (!ufshcd_is_clkgating_allowed(hba))
>  			ufshcd_setup_clocks(hba, true);
>  		ufshcd_release(hba);
>  		pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM : UFS_RUNTIME_PM;
>  		ufshcd_vops_resume(hba, pm_op);
>  	} else {
> -		ufshcd_hold(hba, false);
> +		ufshcd_hold(hba);
>  		if (ufshcd_is_clkscaling_supported(hba) &&
>  		    hba->clk_scaling.is_enabled)
>  			ufshcd_suspend_clkscaling(hba);
> @@ -6239,7 +6207,7 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
>  	}
>  	ufshcd_scsi_block_requests(hba);
>  	/* Drain ufshcd_queuecommand() */
> -	synchronize_rcu();
> +	blk_mq_wait_quiesce_done(&hba->host->tag_set);
>  	cancel_work_sync(&hba->eeh_work);
>  }
>  
> @@ -6884,7 +6852,7 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
>  		return PTR_ERR(req);
>  
>  	req->end_io_data = &wait;
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  
>  	spin_lock_irqsave(host->host_lock, flags);
>  
> @@ -7120,7 +7088,7 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba *hba,
>  		cmd_type = DEV_CMD_TYPE_NOP;
>  		fallthrough;
>  	case UPIU_TRANSACTION_QUERY_REQ:
> -		ufshcd_hold(hba, false);
> +		ufshcd_hold(hba);
>  		mutex_lock(&hba->dev_cmd.lock);
>  		err = ufshcd_issue_devman_upiu_cmd(hba, req_upiu, rsp_upiu,
>  						   desc_buff, buff_len,
> @@ -7186,7 +7154,7 @@ int ufshcd_advanced_rpmb_req_handler(struct ufs_hba *hba, struct utp_upiu_req *r
>  	u16 ehs_len;
>  
>  	/* Protects use of hba->reserved_slot. */
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	mutex_lock(&hba->dev_cmd.lock);
>  	down_read(&hba->clk_scaling_lock);
>  
> @@ -7420,7 +7388,7 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
>  
>  	WARN_ONCE(tag < 0, "Invalid tag %d\n", tag);
>  
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	reg = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
>  	/* If command is already aborted/completed, return FAILED. */
>  	if (!(test_bit(tag, &hba->outstanding_reqs))) {
> @@ -9412,7 +9380,7 @@ static int __ufshcd_wl_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	 * If we can't transition into any of the low power modes
>  	 * just gate the clocks.
>  	 */
> -	ufshcd_hold(hba, false);
> +	ufshcd_hold(hba);
>  	hba->clk_gating.is_suspended = true;
>  
>  	if (ufshcd_is_clkscaling_supported(hba))
> diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
> index db2e669985d5..40c537a3880b 100644
> --- a/include/ufs/ufshcd.h
> +++ b/include/ufs/ufshcd.h
> @@ -1357,7 +1357,7 @@ void ufshcd_fixup_dev_quirks(struct ufs_hba *hba,
>  int ufshcd_read_string_desc(struct ufs_hba *hba, u8 desc_index,
>  			    u8 **buf, bool ascii);
>  
> -int ufshcd_hold(struct ufs_hba *hba, bool async);
> +void ufshcd_hold(struct ufs_hba *hba);
>  void ufshcd_release(struct ufs_hba *hba);
>  
>  void ufshcd_clkgate_delay_set(struct device *dev, unsigned long value);