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

[Shawn Lin]

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.

> 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.

> > +
> > +       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.

Per your comment at patch 4, should I use GENPD_FLAG_ALWAYS_ON +
arm_smccc_smc here in system suspend?

> > +
> > +       return ufshcd_system_suspend(dev);
> > +}
> > +
> > +static const struct dev_pm_ops ufs_rockchip_pm_ops = {
> > +       SET_SYSTEM_SLEEP_PM_OPS(ufs_rockchip_system_suspend, ufshcd_system_resume)
> > +       SET_RUNTIME_PM_OPS(ufs_rockchip_runtime_suspend, ufs_rockchip_runtime_resume, NULL)
> > +       .prepare         = ufshcd_suspend_prepare,
> > +       .complete        = ufshcd_resume_complete,
> > +};
> > +
> > +static struct platform_driver ufs_rockchip_pltform = {
> > +       .probe = ufs_rockchip_probe,
> > +       .remove = ufs_rockchip_remove,
> > +       .driver = {
> > +               .name = "ufshcd-rockchip",
> > +               .pm = &ufs_rockchip_pm_ops,
> > +               .of_match_table = ufs_rockchip_of_match,
> > +       },
> > +};
> > +module_platform_driver(ufs_rockchip_pltform);
> > +
>
> [...]
>
> Kind regards
> Uffe