Re: [PATCH RFC v4 1/1] scsi: ufs: Fix ufs power down/on specs violation

Bjorn Andersson
2020-12-28T17:55:53Z

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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> a Linux Foundation Collaborative Project
>