Message-ID: <6474d14a3055fa645e1004391099ee00@codeaurora.org>
Date:   Tue, 05 Jan 2021 09:39:59 +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 2021-01-05 02:57, Bjorn Andersson wrote:
> On Mon 28 Dec 19:18 CST 2020, 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.
>> 
> 
> I'm not able to find the code you're referring to.

static void exynos_ufs_dev_hw_reset(struct ufs_hba *hba)
{
         struct exynos_ufs *ufs = ufshcd_get_variant(hba);

         hci_writel(ufs, 0 << 0, HCI_GPIO_OUT);
         udelay(5);
         hci_writel(ufs, 1 << 0, HCI_GPIO_OUT);
}

> 
>> >
>> > > +	} 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.
>> 
> 
> Okay, for the resume case I accept that this is a measurable 
> difference.
> I still believe this is a property of the device and not the platform
> though.
> 

True, I also wanted to make the codes simpler and universal for 
everyone...

> Regards,
> Bjorn
> 
>> 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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