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

Can Guo
2020-12-29T01:49:21Z

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@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.
>
> 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
>>>