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Date:   Tue, 29 Dec 2020 09:18:11 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Ziqi Chen <ziqichen@...eaurora.org>, asutoshd@...eaurora.org,
        nguyenb@...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 v4 1/1] scsi: ufs: Fix ufs power down/on specs
 violation

On 2020-12-29 01:55, Bjorn Andersson wrote:
> On Tue 22 Dec 07:49 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, refactor the function
>> ufschd_vops_device_reset(sturct ufs_hba *hba) to ufshcd_
>> vops_device_reset(sturct ufs_hba *hba, bool asserted). The
>> new parameter "bool asserted" 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 | 32 ++++++++++++++++----------------
>>  drivers/scsi/ufs/ufs-qcom.c     | 24 +++++++++++++++---------
>>  drivers/scsi/ufs/ufshcd.c       | 36 
>> +++++++++++++++++++++++++-----------
>>  drivers/scsi/ufs/ufshcd.h       |  8 ++++----
>>  4 files changed, 60 insertions(+), 40 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufs-mediatek.c 
>> b/drivers/scsi/ufs/ufs-mediatek.c
>> index 80618af..072f4db 100644
>> --- a/drivers/scsi/ufs/ufs-mediatek.c
>> +++ b/drivers/scsi/ufs/ufs-mediatek.c
>> @@ -841,27 +841,27 @@ 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_device_reset(struct ufs_hba *hba, bool asserted)
>>  {
>>  	struct arm_smccc_res res;
>> 
>> -	ufs_mtk_device_reset_ctrl(0, res);
>> +	if (asserted) {
>> +		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);
>> +		/*
>> +		 * 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);
> 
> I see no point in allowing vendors to "tweak" the 1us->10us adjustment.
> The specification says 1us and we all agree that 10us gives us good
> enough slack. I.e. this is common code.

Hi Bjron,

We tried, but Samsung fellows wanted 5us. We couldn't get a agreement
on this delay in short term, so we chose to leave it in vops.

> 
>> +	} 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);
> 
> The comment in both the Qualcomm and Mediatek drivers claim that this 
> is
> sleep relates to the UFS device (not host), so why should it be
> different?
> 
> What happens if I take the device that Mediatek see a need for a 10ms
> delay and hook that up to a Qualcomm host? This really should go in the
> common code.
> 

Agree, but Qualcomm host didn't have any problems with 10us yet, so if 
we put
the 10ms delay to common code, Qualcomm host would suffer longer delay 
when
device reset happens - both bootup and resume(xpm_lvl = 5/6) latency 
would
be increased.

Regards,
Can Guo.

> 
> 
> As such I really would prefer to see these delays in the common code!
> You really shouldn't write code based on a speculation that one day
> there might come someone who need other values - when that day come we
> can just change the code, and if it never comes we're better off with
> the cleaner implementation.
> 
> Regards,
> Bjorn
> 
>> +	}
>> 
>>  	return 0;
>>  }
>> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>> index 2206b1e..fed10e5 100644
>> --- a/drivers/scsi/ufs/ufs-qcom.c
>> +++ b/drivers/scsi/ufs/ufs-qcom.c
>> @@ -1406,10 +1406,11 @@ static void ufs_qcom_dump_dbg_regs(struct 
>> ufs_hba *hba)
>>  /**
>>   * ufs_qcom_device_reset() - toggle the (optional) device reset line
>>   * @hba: per-adapter instance
>> + * @asserted: assert or deassert 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_device_reset(struct ufs_hba *hba, bool asserted)
>>  {
>>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
>> 
>> @@ -1417,15 +1418,20 @@ 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);
>> +	if (asserted) {
>> +		gpiod_set_value_cansleep(host->device_reset, 1);
>> 
>> -	gpiod_set_value_cansleep(host->device_reset, 0);
>> -	usleep_range(10, 15);
>> +		/*
>> +		 * The UFS device shall detect reset pulses of 1us, sleep for 10us 
>> to
>> +		 * be on the safe side.
>> +		 */
>> +		usleep_range(10, 15);
>> +	} else {
>> +		gpiod_set_value_cansleep(host->device_reset, 0);
>> +
>> +		 /* Some devices may need time to respond to rst_n */
>> +		usleep_range(10, 15);
>> +	}
>> 
>>  	return 0;
>>  }
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index e221add..f2daac2 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -585,7 +585,13 @@ static void ufshcd_device_reset(struct ufs_hba 
>> *hba)
>>  {
>>  	int err;
>> 
>> -	err = ufshcd_vops_device_reset(hba);
>> +	err = ufshcd_vops_device_reset(hba, true);
>> +	if (err) {
>> +		dev_err(hba->dev, "asserting device reset failed: %d\n", err);
>> +		return;
>> +	}
>> +
>> +	err = ufshcd_vops_device_reset(hba, false);
>> 
>>  	if (!err) {
>>  		ufshcd_set_ufs_dev_active(hba);
>> @@ -593,7 +599,11 @@ static void ufshcd_device_reset(struct ufs_hba 
>> *hba)
>>  			hba->wb_enabled = false;
>>  			hba->wb_buf_flush_enabled = false;
>>  		}
>> +		dev_dbg(hba->dev, "device reset done\n");
>> +	} else {
>> +		dev_err(hba->dev, "deasserting device reset failed: %d\n", err);
>>  	}
>> +
>>  	if (err != -EOPNOTSUPP)
>>  		ufshcd_update_evt_hist(hba, UFS_EVT_DEV_RESET, err);
>>  }
>> @@ -8686,8 +8696,6 @@ 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 +8711,9 @@ 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_device_reset(hba, true);
>> +
>>  	ufshcd_setup_clocks(hba, false);
>> 
>>  	if (ufshcd_is_clkgating_allowed(hba)) {
>> @@ -8711,6 +8722,8 @@ 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 +8791,19 @@ 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 +8811,7 @@ 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 +8878,6 @@ 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 +8888,8 @@ 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..d5fbaba 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
>> + * @device_reset: called to assert or deassert device reset line
>>   * @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	(*device_reset)(struct ufs_hba *hba, bool asserted);
>>  	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_device_reset(struct ufs_hba *hba, bool 
>> asserted)
>>  {
>>  	if (hba->vops && hba->vops->device_reset)
>> -		return hba->vops->device_reset(hba);
>> +		return hba->vops->device_reset(hba, asserted);
>> 
>>  	return -EOPNOTSUPP;
>>  }
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 

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