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Date:   Tue, 29 Dec 2020 09:48:08 +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 09:18, Can Guo wrote:
> 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.
> 

Besides, currently this device reset vops is only registered by 
ufs-qcom.c
and ufs-mediatek.c, meaning any delays that we put in the common code 
are not
necessary for those who do not have this vops registered, i.e 
ufs-exynos.c,
ufs-hisi.c.

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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