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Date:   Mon, 28 Dec 2020 11:55:04 -0600
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Ziqi Chen <ziqichen@codeaurora.org>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        cang@codeaurora.org, hongwus@codeaurora.org, rnayak@codeaurora.org,
        vinholikatti@gmail.com, jejb@linux.vnet.ibm.com,
        martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
        kernel-team@android.com, saravanak@google.com, salyzyn@google.com,
        kwmad.kim@samsung.com, stanley.chu@mediatek.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        Andy Gross <agross@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Bean Huo <beanhuo@micron.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Satya Tangirala <satyat@google.com>,
        "moderated list:UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER..." 
        <linux-mediatek@lists.infradead.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@vger.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH RFC v4 1/1] scsi: ufs: Fix ufs power down/on specs
 violation
Message-ID: <X+ob+FylvPfl3NR/@builder.lan>
References: <1608644981-46267-1-git-send-email-ziqichen@codeaurora.org>
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In-Reply-To: <1608644981-46267-1-git-send-email-ziqichen@codeaurora.org>
Precedence: bulk

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@samsung.com>
> Cc: Stanley Chu <stanley.chu@mediatek.com>
> Signed-off-by: Ziqi Chen <ziqichen@codeaurora.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.

> +	} 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.


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;
>  }
> -- 
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