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Date:   Tue, 22 Dec 2020 11:08:52 +0800
From:   ziqichen@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        cang@...eaurora.org, hongwus@...eaurora.org, rnayak@...eaurora.org,
        vinholikatti@...il.com, jejb@...ux.vnet.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
        kwmad.kim@...sung.com, stanley.chu@...iatek.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Andy Gross <agross@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Bean Huo <beanhuo@...ron.com>,
        Bart Van Assche <bvanassche@....org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Satya Tangirala <satyat@...gle.com>,
        "moderated list:UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER..." 
        <linux-mediatek@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH RFC v3 1/1] scsi: ufs: Fix ufs power down/on specs
 violation

On 2020-12-22 02:41, Bjorn Andersson wrote:
> On Mon 21 Dec 01:51 CST 2020, Ziqi Chen wrote:
> 
>> As per specs, e.g, JESD220E chapter 7.2, while powering
>> off/on the ufs device, RST_N signal and REF_CLK signal
>> should be between VSS(Ground) and VCCQ/VCCQ2.
>> 
>> To flexibly control device reset line, re-name the function
>> ufschd_vops_device_reset(sturct ufs_hba *hba) to ufshcd_
>> vops_toggle_device_reset(sturct ufs_hba *hba, bool down). The
>> new parameter "bool down" is used to separate device reset
>> line pulling down from pulling up.
>> 
>> Cc: Kiwoong Kim <kwmad.kim@...sung.com>
>> Cc: Stanley Chu <stanley.chu@...iatek.com>
>> Signed-off-by: Ziqi Chen <ziqichen@...eaurora.org>
>> ---
>>  drivers/scsi/ufs/ufs-mediatek.c | 27 +++++++++-----------------
>>  drivers/scsi/ufs/ufs-qcom.c     | 22 ++++++++++-----------
>>  drivers/scsi/ufs/ufshcd.c       | 43 
>> ++++++++++++++++++++++++++++++-----------
>>  drivers/scsi/ufs/ufshcd.h       | 10 +++++-----
>>  4 files changed, 56 insertions(+), 46 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufs-mediatek.c 
>> b/drivers/scsi/ufs/ufs-mediatek.c
>> index 80618af..bff2c42 100644
>> --- a/drivers/scsi/ufs/ufs-mediatek.c
>> +++ b/drivers/scsi/ufs/ufs-mediatek.c
>> @@ -841,27 +841,18 @@ static int ufs_mtk_link_startup_notify(struct 
>> ufs_hba *hba,
>>  	return ret;
>>  }
>> 
>> -static int ufs_mtk_device_reset(struct ufs_hba *hba)
>> +static int ufs_mtk_toggle_device_reset(struct ufs_hba *hba, bool 
>> down)
>>  {
>>  	struct arm_smccc_res res;
>> 
>> -	ufs_mtk_device_reset_ctrl(0, res);
>> -
>> -	/*
>> -	 * The reset signal is active low. UFS devices shall detect
>> -	 * more than or equal to 1us of positive or negative RST_n
>> -	 * pulse width.
>> -	 *
>> -	 * To be on safe side, keep the reset low for at least 10us.
>> -	 */
>> -	usleep_range(10, 15);
>> -
>> -	ufs_mtk_device_reset_ctrl(1, res);
>> -
>> -	/* Some devices may need time to respond to rst_n */
>> -	usleep_range(10000, 15000);
>> +	if (down) {
>> +		ufs_mtk_device_reset_ctrl(0, res);
>> +	} else {
>> +		ufs_mtk_device_reset_ctrl(1, res);
>> 
>> -	dev_info(hba->dev, "device reset done\n");
>> +		/* Some devices may need time to respond to rst_n */
>> +		usleep_range(10000, 15000);
>> +	}
>> 
>>  	return 0;
>>  }
>> @@ -1052,7 +1043,7 @@ static const struct ufs_hba_variant_ops 
>> ufs_hba_mtk_vops = {
>>  	.suspend             = ufs_mtk_suspend,
>>  	.resume              = ufs_mtk_resume,
>>  	.dbg_register_dump   = ufs_mtk_dbg_register_dump,
>> -	.device_reset        = ufs_mtk_device_reset,
>> +	.toggle_device_reset        = ufs_mtk_toggle_device_reset,
>>  	.event_notify        = ufs_mtk_event_notify,
>>  };
>> 
>> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>> index 2206b1e..c2ccaa5 100644
>> --- a/drivers/scsi/ufs/ufs-qcom.c
>> +++ b/drivers/scsi/ufs/ufs-qcom.c
>> @@ -1404,12 +1404,13 @@ static void ufs_qcom_dump_dbg_regs(struct 
>> ufs_hba *hba)
>>  }
>> 
>>  /**
>> - * ufs_qcom_device_reset() - toggle the (optional) device reset line
>> + * ufs_qcom_toggle_device_reset() - toggle the (optional) device 
>> reset line
>>   * @hba: per-adapter instance
>> + * @down: pull down or pull up device reset line
>>   *
>>   * Toggles the (optional) reset line to reset the attached device.
>>   */
>> -static int ufs_qcom_device_reset(struct ufs_hba *hba)
>> +static int ufs_qcom_toggle_device_reset(struct ufs_hba *hba, bool 
>> down)
>>  {
>>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
>> 
>> @@ -1417,15 +1418,12 @@ static int ufs_qcom_device_reset(struct 
>> ufs_hba *hba)
>>  	if (!host->device_reset)
>>  		return -EOPNOTSUPP;
>> 
>> -	/*
>> -	 * The UFS device shall detect reset pulses of 1us, sleep for 10us 
>> to
>> -	 * be on the safe side.
>> -	 */
>> -	gpiod_set_value_cansleep(host->device_reset, 1);
>> -	usleep_range(10, 15);
>> -
>> -	gpiod_set_value_cansleep(host->device_reset, 0);
>> -	usleep_range(10, 15);
>> +	if (down) {
>> +		gpiod_set_value_cansleep(host->device_reset, 1);
>> +	} else {
>> +		gpiod_set_value_cansleep(host->device_reset, 0);
>> +		usleep_range(10, 15);
> 
> The comment above describes that the reset pulse should be 10uS, so the
> only reason I can see for the sleep here would be for devices to come
> back up after the reset pulse - i.e. what Mediatek believes needs
> 10-15mS.
> 
> As such, I would like you to move this sleep out to the caller and then
> turns this snippet into just:
> 
> 	gpiod_set_value_cansleep(host->device_reset, down);
> 
> I don't see a problem using Mediatek's reasoning and sleep values in 
> the
> common case.

Understood. It would better to move this sleep (10-15ms)out to the 
caller and
simplify this function.

> 
>> +	}
>> 
>>  	return 0;
>>  }
>> @@ -1473,7 +1471,7 @@ static const struct ufs_hba_variant_ops 
>> ufs_hba_qcom_vops = {
>>  	.suspend		= ufs_qcom_suspend,
>>  	.resume			= ufs_qcom_resume,
>>  	.dbg_register_dump	= ufs_qcom_dump_dbg_regs,
>> -	.device_reset		= ufs_qcom_device_reset,
>> +	.toggle_device_reset		= ufs_qcom_toggle_device_reset,
>>  	.config_scaling_param = ufs_qcom_config_scaling_param,
>>  	.program_key		= ufs_qcom_ice_program_key,
>>  };
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index e221add..2ee905f 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -585,7 +585,20 @@ static void ufshcd_device_reset(struct ufs_hba 
>> *hba)
>>  {
>>  	int err;
>> 
>> -	err = ufshcd_vops_device_reset(hba);
>> +	err = ufshcd_vops_toggle_device_reset(hba, true);
>> +	if (err) {
>> +		dev_err(hba->dev, "device reset pulling down failure: %d\n", err);
> 
> "asserting device reset failed"

Agree, thanks.

> 
>> +		return;
>> +	}
>> +
>> +	/*
>> +	 * The reset signal is active low. The UFS device
>> +	 * shall detect reset pulses of 1us, sleep for at
>> +	 * least 10us to be on the safe side.
>> +	 */
>> +	usleep_range(10, 15);
>> +
>> +	err = ufshcd_vops_toggle_device_reset(hba, false);
>> 
>>  	if (!err) {
>>  		ufshcd_set_ufs_dev_active(hba);
>> @@ -593,7 +606,11 @@ static void ufshcd_device_reset(struct ufs_hba 
>> *hba)
>>  			hba->wb_enabled = false;
>>  			hba->wb_buf_flush_enabled = false;
>>  		}
>> +		dev_info(hba->dev, "device reset done\n");
> 
> Please use dev_dbg(), as this is only interesting to us when we're
> actually debugging UFS related issues.

Agree, thanks.

> 
>> +	} else {
>> +		dev_err(hba->dev, "device reset pulling up failure: %d\n", err);
> 
> "deasserting device reset failed"

Agree, thanks.

> 
>>  	}
>> +
>>  	if (err != -EOPNOTSUPP)
>>  		ufshcd_update_evt_hist(hba, UFS_EVT_DEV_RESET, err);
>>  }
>> @@ -8686,8 +8703,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	if (ret)
>>  		goto set_dev_active;
>> 
>> -	ufshcd_vreg_set_lpm(hba);
>> -
>>  disable_clks:
>>  	/*
>>  	 * Call vendor specific suspend callback. As these callbacks may 
>> access
>> @@ -8703,6 +8718,9 @@ static int ufshcd_suspend(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	 */
>>  	ufshcd_disable_irq(hba);
>> 
>> +	if (ufshcd_is_link_off(hba))
>> +		ufshcd_vops_toggle_device_reset(hba, true);
>> +
>>  	ufshcd_setup_clocks(hba, false);
>> 
>>  	if (ufshcd_is_clkgating_allowed(hba)) {
>> @@ -8711,6 +8729,8 @@ static int ufshcd_suspend(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  					hba->clk_gating.state);
>>  	}
>> 
>> +	ufshcd_vreg_set_lpm(hba);
>> +
>>  	/* Put the host controller in low power mode if possible */
>>  	ufshcd_hba_vreg_set_lpm(hba);
>>  	goto out;
>> @@ -8778,18 +8798,19 @@ static int ufshcd_resume(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	old_link_state = hba->uic_link_state;
>> 
>>  	ufshcd_hba_vreg_set_hpm(hba);
>> +
>> +	ret = ufshcd_vreg_set_hpm(hba);
>> +	if (ret)
>> +		goto out;
>> +
>>  	/* Make sure clocks are enabled before accessing controller */
>>  	ret = ufshcd_setup_clocks(hba, true);
>>  	if (ret)
>> -		goto out;
>> +		goto disable_vreg;
>> 
>>  	/* enable the host irq as host controller would be active soon */
>>  	ufshcd_enable_irq(hba);
>> 
>> -	ret = ufshcd_vreg_set_hpm(hba);
>> -	if (ret)
>> -		goto disable_irq_and_vops_clks;
>> -
>>  	/*
>>  	 * Call vendor specific resume callback. As these callbacks may 
>> access
>>  	 * vendor specific host controller register space call them when the
>> @@ -8797,7 +8818,7 @@ static int ufshcd_resume(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	 */
>>  	ret = ufshcd_vops_resume(hba, pm_op);
>>  	if (ret)
>> -		goto disable_vreg;
>> +		goto disable_irq_and_vops_clks;
>> 
>>  	/* For DeepSleep, the only supported option is to have the link off 
>> */
>>  	WARN_ON(ufshcd_is_ufs_dev_deepsleep(hba) && 
>> !ufshcd_is_link_off(hba));
>> @@ -8864,8 +8885,6 @@ static int ufshcd_resume(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	ufshcd_link_state_transition(hba, old_link_state, 0);
>>  vendor_suspend:
>>  	ufshcd_vops_suspend(hba, pm_op);
>> -disable_vreg:
>> -	ufshcd_vreg_set_lpm(hba);
>>  disable_irq_and_vops_clks:
>>  	ufshcd_disable_irq(hba);
>>  	if (hba->clk_scaling.is_allowed)
>> @@ -8876,6 +8895,8 @@ static int ufshcd_resume(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  		trace_ufshcd_clk_gating(dev_name(hba->dev),
>>  					hba->clk_gating.state);
>>  	}
>> +disable_vreg:
>> +	ufshcd_vreg_set_lpm(hba);
>>  out:
>>  	hba->pm_op_in_progress = 0;
>>  	if (ret)
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index 9bb5f0e..dccc3eb 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -319,7 +319,7 @@ struct ufs_pwr_mode_info {
>>   * @resume: called during host controller PM callback
>>   * @dbg_register_dump: used to dump controller debug information
>>   * @phy_initialization: used to initialize phys
>> - * @device_reset: called to issue a reset pulse on the UFS device
>> + * @toggle_device_reset: called to change logic level of reset gpio 
>> on the UFS device
>>   * @program_key: program or evict an inline encryption key
>>   * @event_notify: called to notify important events
>>   */
>> @@ -350,7 +350,7 @@ struct ufs_hba_variant_ops {
>>  	int     (*resume)(struct ufs_hba *, enum ufs_pm_op);
>>  	void	(*dbg_register_dump)(struct ufs_hba *hba);
>>  	int	(*phy_initialization)(struct ufs_hba *);
>> -	int	(*device_reset)(struct ufs_hba *hba);
>> +	int	(*toggle_device_reset)(struct ufs_hba *hba, bool down);
> 
> I don't think "toggle" adds any value to the understanding of what this
> function is expected to do, so I would prefer that you just keep it
> "device_reset".
> 
> I also would prefer that you replace "down" with "asserted" - as this
> avoids questions about active high/low etc from the API.
> 
> Thanks,
> Bjorn

Agree, thanks.

Best Regards,
Ziqi


> 
>>  	void	(*config_scaling_param)(struct ufs_hba *hba,
>>  					struct devfreq_dev_profile *profile,
>>  					void *data);
>> @@ -1216,10 +1216,10 @@ static inline void 
>> ufshcd_vops_dbg_register_dump(struct ufs_hba *hba)
>>  		hba->vops->dbg_register_dump(hba);
>>  }
>> 
>> -static inline int ufshcd_vops_device_reset(struct ufs_hba *hba)
>> +static inline int ufshcd_vops_toggle_device_reset(struct ufs_hba 
>> *hba, bool down)
>>  {
>> -	if (hba->vops && hba->vops->device_reset)
>> -		return hba->vops->device_reset(hba);
>> +	if (hba->vops && hba->vops->toggle_device_reset)
>> +		return hba->vops->toggle_device_reset(hba, down);
>> 
>>  	return -EOPNOTSUPP;
>>  }
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 

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