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

Can Guo
2020-12-29T01:19:08Z

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.

>
>
> 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
>>