[PATCH v3 2/3] phy: qcom-snps-femto-v2: add system sleep PM ops
Bjorn Andersson
andersson at kernel.org
Tue Jun 27 16:06:00 PDT 2023
On Tue, Jun 27, 2023 at 02:08:41PM -0400, Adrien Thierry wrote:
> Hi Bjorn,
>
> On Thu, Jun 22, 2023 at 02:43:07PM -0700, Bjorn Andersson wrote:
> > On Thu, Jun 22, 2023 at 03:40:19PM -0400, Adrien Thierry wrote:
> > > The downstream driver [1] implements set_suspend(), which deals with
> > > both runtime and system sleep/resume. The upstream driver already has
> > > runtime PM ops, so add the system sleep PM ops as well, reusing the same
> > > code as the runtime PM ops.
> > >
> > > [1] https://git.codelinaro.org/clo/la/kernel/msm-5.4/-/blob/LV.AU.1.2.1.r2-05300-gen3meta.0/drivers/usb/phy/phy-msm-snps-hs.c
> > >
> > > Signed-off-by: Adrien Thierry <athierry at redhat.com>
> > > ---
> > > drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c | 18 ++++++++++--------
> > > 1 file changed, 10 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c b/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c
> > > index ce1d2f8b568a..378a5029f61e 100644
> > > --- a/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c
> > > +++ b/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c
> > > @@ -179,7 +179,7 @@ static inline void qcom_snps_hsphy_write_mask(void __iomem *base, u32 offset,
> > > readl_relaxed(base + offset);
> > > }
> > >
> > > -static int qcom_snps_hsphy_suspend(struct qcom_snps_hsphy *hsphy)
> > > +static int qcom_snps_hsphy_do_suspend(struct qcom_snps_hsphy *hsphy)
> > > {
> > > dev_dbg(&hsphy->phy->dev, "Suspend QCOM SNPS PHY\n");
> > >
> > > @@ -199,7 +199,7 @@ static int qcom_snps_hsphy_suspend(struct qcom_snps_hsphy *hsphy)
> > > return 0;
> > > }
> > >
> > > -static int qcom_snps_hsphy_resume(struct qcom_snps_hsphy *hsphy)
> > > +static int qcom_snps_hsphy_do_resume(struct qcom_snps_hsphy *hsphy)
> > > {
> > > int ret;
> > >
> > > @@ -214,25 +214,25 @@ static int qcom_snps_hsphy_resume(struct qcom_snps_hsphy *hsphy)
> > > return 0;
> > > }
> > >
> > > -static int __maybe_unused qcom_snps_hsphy_runtime_suspend(struct device *dev)
> > > +static int __maybe_unused qcom_snps_hsphy_suspend(struct device *dev)
> > > {
> > > struct qcom_snps_hsphy *hsphy = dev_get_drvdata(dev);
> > >
> > > if (!hsphy->phy_initialized)
> > > return 0;
> > >
> > > - qcom_snps_hsphy_suspend(hsphy);
> > > + qcom_snps_hsphy_do_suspend(hsphy);
> > > return 0;
> > > }
> > >
> > > -static int __maybe_unused qcom_snps_hsphy_runtime_resume(struct device *dev)
> > > +static int __maybe_unused qcom_snps_hsphy_resume(struct device *dev)
> > > {
> > > struct qcom_snps_hsphy *hsphy = dev_get_drvdata(dev);
> > >
> > > if (!hsphy->phy_initialized)
> > > return 0;
> > >
> > > - qcom_snps_hsphy_resume(hsphy);
> > > + qcom_snps_hsphy_do_resume(hsphy);
> > > return 0;
> > > }
> > >
> > > @@ -518,8 +518,10 @@ static const struct of_device_id qcom_snps_hsphy_of_match_table[] = {
> > > MODULE_DEVICE_TABLE(of, qcom_snps_hsphy_of_match_table);
> > >
> > > static const struct dev_pm_ops qcom_snps_hsphy_pm_ops = {
> > > - SET_RUNTIME_PM_OPS(qcom_snps_hsphy_runtime_suspend,
> > > - qcom_snps_hsphy_runtime_resume, NULL)
> > > + SET_RUNTIME_PM_OPS(qcom_snps_hsphy_suspend,
> > > + qcom_snps_hsphy_resume, NULL)
> > > + SET_SYSTEM_SLEEP_PM_OPS(qcom_snps_hsphy_suspend,
> > > + qcom_snps_hsphy_resume)
> >
> > Won't this cause issues if you system suspend the device while it's
> > already runtime suspended?
> >
>
> I'm not sure if it would cause issues, but after reflexion and discussion
> with Andrew, I think it's unnecessary to add system PM ops in the femto
> PHY driver.
>
Glad you looked further into this, I had a brief chat with Andrew and
was building a similar understanding.
> In the dwc3 core, both system and runtime suspend end up calling
> dwc3_suspend_common(). From there, what happens depends on the USB mode
> and whether the controller is entering system or runtime suspend.
>
> HOST mode:
> (1) system suspend on a non-wakeup controller
>
> The [1] if branch is taken. dwc3_core_exit() is called, which ends up
> calling phy_power_off() and phy_exit(). Those two functions decrease the
> PM runtime count at some point, so they will trigger the PHY runtime sleep
> (assuming the count is right).
>
> (2) runtime suspend / system suspend on a wakeup controller
>
> The [1] branch is not taken. dwc3_suspend_common() calls
> phy_pm_runtime_put_sync(dwc->usb2_generic_phy). Assuming the ref count is
> right, the PHY runtime suspend op is called.
>
> DEVICE mode:
>
> dwc3_core_exit() is called on both runtime and system sleep
> unless the controller is already runtime suspended.
>
> OTG mode:
> (1) system suspend : dwc3_core_exit() is called
>
> (2) runtime suspend : do nothing
>
> With that in mind:
>
> 1) Does the PHY need to implement system sleep callbacks?
>
> dwc3 core system sleep callback will already runtime suspend the PHY, and
> also call phy_power_off() and phy_exit() for non-wakeup controllers. So,
> adding system PM ops to the femto PHY driver would be redundant.
>
It seems these decisions must come from the controller, in order to
handle the differences between a wakeup capable port and not. So I'm
thinking that it's correct that it should not implement this.
> 2) Should the ref_clk be disabled for runtime sleep / wakeup controller
> system sleep, or only for non-wakeup controller system sleep?
>
> I'm a little hesitant here. In my submission I'm disabling it in both, but
> looking at the downstream code you provided, it seems it's only disabled
> for system sleep. ref_clk is disabled by phy->set_suspend() [2] which IIUC
> is only called in the system sleep path through dwc3_core_exit() [3].
> Moreover, in host mode the upstream code seems to make a distinction
> between 1) runtime sleep / system sleep for wakeup controller, and 2)
> system sleep for non-wakeup controller where phy_power_off() and
> phy_exit() are only called in the latter. This suggests the PHY is not
> supposed to be in a fully powered-off state for runtime sleep and system
> sleep for wakeup controller. So, it's possible the ref_clk should be kept
> enabled in this case. What is your take on this? I could only disable
> ref_clk in the femto phy->exit() callback to keep ref_clk enabled during
> runtime sleep and make sure it's only disabled on system sleep for
> non-wakeup controller.
>
I suggested the same to Andrew, in our chat. Keeping sufficient
resources on, to allow the system to be woken up again by a USB device
is needed if requested. As such the handling of ref must differ between
the two cases.
It still looks a bit strange to me, having the runtime PM callbacks
prepare for wakeup from system suspend...
> Hoping I'm not missing anything here.
>
I think you managed to capture it all. Sorry for leading you down this
incorrect path.
Regards,
Bjorn
> Best,
>
> Adrien
>
> [1] https://elixir.bootlin.com/linux/latest/source/drivers/usb/dwc3/core.c#L1988
> [2] https://git.codelinaro.org/clo/la/kernel/msm-5.4/-/blob/LV.AU.1.2.1.r2-05300-gen3meta.0/drivers/usb/phy/phy-msm-snps-hs.c#L524
> [3] https://git.codelinaro.org/clo/la/kernel/msm-5.4/-/blob/LV.AU.1.2.1.r2-05300-gen3meta.0/drivers/usb/dwc3/core.c#L1915
>
> > Regards,
> > Bjorn
> >
> > > };
> > >
> > > static void qcom_snps_hsphy_override_param_update_val(
> > > --
> > > 2.40.1
> > >
>
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