Message-ID: <20241103120223.abkwgej4svas4epr@thinkpad>
Date: Sun, 3 Nov 2024 17:32:23 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Shawn Lin <shawn.lin@...k-chips.com>
Cc: Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh+dt@...nel.org>,
	"James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Avri Altman <avri.altman@....com>,
	Bart Van Assche <bvanassche@....org>,
	YiFeng Zhao <zyf@...k-chips.com>, Liang Chen <cl@...k-chips.com>,
	linux-scsi@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 5/5] scsi: ufs: rockchip: initial support for UFS

On Fri, Oct 18, 2024 at 05:20:08PM +0800, Shawn Lin 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@...k-chips.com> 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.
> 

We had a requirement to notify the genpd provider from consumer to not turn off
the power domain during system suspend. So Ulf came up with an API for
consumers, device_set_wakeup_path() setting the 'dev->power.wakeup_path' which
will be honored by the genpd core. Will that work for you?

PS: The API naming suggests that the device will be used in wakeup path, which
may not be true here but the end result will be the same.

- Mani

-- 
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