Re: [PATCH v3 5/5] scsi: ufs: rockchip: initial support for UFS

From: Shawn Lin
Date: Mon Nov 04 2024 - 08:12:04 EST

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在 2024/11/1 23:12, Ulf Hansson 写道:

On Mon, 21 Oct 2024 at 02:43, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:

在 2024/10/18 18:03, Ulf Hansson 写道:

On Fri, 18 Oct 2024 at 11:20, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:

Hi Ulf,

在 2024/10/18 17:07, Ulf Hansson 写道:

On Thu, 10 Oct 2024 at 03:21, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:

Hi Ulf

在 2024/10/9 21:15, Ulf Hansson 写道:

[...]

+
+static int ufs_rockchip_runtime_suspend(struct device *dev)
+{
+ struct ufs_hba *hba = dev_get_drvdata(dev);
+ struct ufs_rockchip_host *host = ufshcd_get_variant(hba);
+ struct generic_pm_domain *genpd = pd_to_genpd(dev->pm_domain);

pd_to_genpd() isn't safe to use like this. It's solely to be used by
genpd provider drivers.

+
+ clk_disable_unprepare(host->ref_out_clk);
+
+ /*
+ * Shouldn't power down if rpm_lvl is less than level 5.

Can you elaborate on why we must not power-off the power-domain when
level is less than 5?

Because ufshcd driver assume the controller is active and the link is on
if level is less than 5. So the default resume policy will not try to
recover the registers until the first error happened. Otherwise if the
level is >=5, it assumes the controller is off and the link is down,
then it will restore the registers and link.

And the level is changeable via sysfs.

Okay, thanks for clarifying.

What happens if we power-off anyway when the level is less than 5?

+ * This flag will be passed down to platform power-domain driver
+ * which has the final decision.
+ */
+ if (hba->rpm_lvl < UFS_PM_LVL_5)
+ genpd->flags |= GENPD_FLAG_RPM_ALWAYS_ON;
+ else
+ genpd->flags &= ~GENPD_FLAG_RPM_ALWAYS_ON;

The genpd->flags is not supposed to be changed like this - and
especially not from a genpd consumer driver.

I am trying to understand a bit more of the use case here. Let's see
if that helps me to potentially suggest an alternative approach.

I was not familiar with the genpd part, so I haven't come up with
another solution. It would be great if you can guide me to the right
way.

I have been playing with the existing infrastructure we have at hand
to support this, but I need a few more days to be able to propose
something for you.

Much appreciate.

+
+ return ufshcd_runtime_suspend(dev);
+}
+
+static int ufs_rockchip_runtime_resume(struct device *dev)
+{
+ struct ufs_hba *hba = dev_get_drvdata(dev);
+ struct ufs_rockchip_host *host = ufshcd_get_variant(hba);
+ int err;
+
+ err = clk_prepare_enable(host->ref_out_clk);
+ if (err) {
+ dev_err(hba->dev, "failed to enable ref out clock %d\n", err);
+ return err;
+ }
+
+ reset_control_assert(host->rst);
+ usleep_range(1, 2);
+ reset_control_deassert(host->rst);
+
+ return ufshcd_runtime_resume(dev);
+}
+
+static int ufs_rockchip_system_suspend(struct device *dev)
+{
+ struct ufs_hba *hba = dev_get_drvdata(dev);
+ struct ufs_rockchip_host *host = ufshcd_get_variant(hba);
+
+ /* Pass down desired spm_lvl to Firmware */
+ arm_smccc_smc(ROCKCHIP_SIP_SUSPEND_MODE, ROCKCHIP_SLEEP_PD_CONFIG,
+ host->pd_id, hba->spm_lvl < 5 ? 1 : 0, 0, 0, 0, 0, NULL);

Can you please elaborate on what goes on here? Is this turning off the
power-domain that the dev is attached to - or what is actually
happening?

This smc call is trying to ask firmware not to turn off the power-domian
that the UFS is attached to and also not to turn off the power of UFS
conntroller.

Okay, thanks for clarifying!

A follow up question, don't you need to make a corresponding smc call
to inform the FW that it's okay to turn off the power-domain at some
point?

Yes. Each time entering sleep, we teach FW if it need to turn off or
keep power-domain, for instance "hba->spm_lvl < 5 ? 1 : 0" , 0 means
off and 1 means on.

I see. So you need to make the call each time when entering the system suspend?

Or would it be okay to just make it once, when the spm_lvl is changed?

Thers is no nofity when changing spm_lvl.

Another way to deal with it, would be to make the smc call each time
the power-domain is turned-on, based on spm_lvl too of course.

Would that work?

Yes, that works. Another option is to cache power-domain states and
check spm_lvl locally. If it doesn't change, we skip smc call.

Apologize for the delay! I needed to think a bit more carefully about
how to suggest moving this forward.

My conclusion is that we need to extend the PM domain infrastructure
(genpd in particular), to allow drivers to dynamically inform whether
it's okay to turn on/off the PM domain in runtime.

There is a similar thing already available, which is to use dev PM qos
along with the genpd governor, but that would not work in this case
because it may prevent runtime suspend for the device in question too.
I have therefore cooked a patch for genpd, see below. I think you can
fold it into your next version of the series. See also additional
suggestions below the patch.

Thanks, Ulf. I'll fold it into my v4 series and fix the code in UFS driver and genpd provider according to your suggestions.

From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Date: Fri, 1 Nov 2024 15:55:56 +0100
Subject: [PATCH] pmdomain: core: Introduce dev_pm_genpd_rpm_always_on()

For some usecases a consumer driver requires its device to remain power-on
from the PM domain perspective during runtime. Using dev PM qos along with
the genpd governors, doesn't work for this case as would potentially
prevent the device from being runtime suspended too.

To support these usecases, let's introduce dev_pm_genpd_rpm_always_on() to
allow consumers drivers to dynamically control the behaviour in genpd for a
device that is attached to it.

Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
---
drivers/pmdomain/core.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/pm_domain.h | 7 +++++++
2 files changed, 41 insertions(+)

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index a6c8b85dd024..e86e270b7eb9 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -697,6 +697,36 @@ bool dev_pm_genpd_get_hwmode(struct device *dev)
}
EXPORT_SYMBOL_GPL(dev_pm_genpd_get_hwmode);

+/**
+ * dev_pm_genpd_rpm_always_on() - Control if the PM domain can be powered off.
+ *
+ * @dev: Device for which the PM domain may need to stay on for.
+ * @on: Value to set or unset for the condition.
+ *
+ * For some usecases a consumer driver requires its device to remain power-on
+ * from the PM domain perspective during runtime. This function allows the
+ * behaviour to be dynamically controlled for a device attached to a genpd.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Return: Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
+{
+ struct generic_pm_domain *genpd;
+
+ genpd = dev_to_genpd_safe(dev);
+ if (!genpd)
+ return -ENODEV;
+
+ genpd_lock(genpd);
+ dev_gpd_data(dev)->rpm_always_on = on;
+ genpd_unlock(genpd);
+
+ return 0;
+}
+
static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
{
unsigned int state_idx = genpd->state_idx;
@@ -868,6 +898,10 @@ static int genpd_power_off(struct
generic_pm_domain *genpd, bool one_dev_on,
if (!pm_runtime_suspended(pdd->dev) ||
irq_safe_dev_in_sleep_domain(pdd->dev, genpd))
not_suspended++;
+
+ /* The device may need its PM domain to stay powered on. */
+ if (to_gpd_data(pdd)->rpm_always_on)
+ return -EBUSY;
}

if (not_suspended > 1 || (not_suspended == 1 && !one_dev_on))
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 45646bfcaf1a..d4c4a7cf34bd 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -260,6 +260,7 @@ struct generic_pm_domain_data {
unsigned int rpm_pstate;
unsigned int opp_token;
bool hw_mode;
+ bool rpm_always_on;
void *data;
};

@@ -292,6 +293,7 @@ ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
void dev_pm_genpd_synced_poweroff(struct device *dev);
int dev_pm_genpd_set_hwmode(struct device *dev, bool enable);
bool dev_pm_genpd_get_hwmode(struct device *dev);
+int dev_pm_genpd_rpm_always_on(struct device *dev, bool on);

extern struct dev_power_governor simple_qos_governor;
extern struct dev_power_governor pm_domain_always_on_gov;
@@ -375,6 +377,11 @@ static inline bool dev_pm_genpd_get_hwmode(struct
device *dev)
return false;
}

+static inline int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
+{
+ return -EOPNOTSUPP;
+}
+
#define simple_qos_governor (*(struct dev_power_governor *)(NULL))
#define pm_domain_always_on_gov (*(struct
dev_power_governor *)(NULL))
#endif

Next message: Huang, Ying: "Re: [PATCH RFC] mm: mitigate large folios usage and swap thrashing for nearly full memcg"
Previous message: Andy Shevchenko: "Re: [PATCH v1 1/1] media: atomisp: Remove License information boilerplate"
In reply to: Ulf Hansson: "Re: [PATCH v3 5/5] scsi: ufs: rockchip: initial support for UFS"
Next in thread: Manivannan Sadhasivam: "Re: [PATCH v3 5/5] scsi: ufs: rockchip: initial support for UFS"
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