Re: [PATCH v1] pmdomain: imx8m-blk-ctrl: fix suspend/resume order

[Ulf Hansson]

On Thu, 18 Apr 2024 at 17:52, Vitor Soares <ivitro@xxxxxxxxx> wrote:
>
> From: Vitor Soares <vitor.soares@xxxxxxxxxxx>
>
> During the probe, the genpd power_dev is added to the dpm_list after
> blk_ctrl due to its parent/child relationship. Making the blk_ctrl
> suspend after and resume before the genpd power_dev.
>
> As a consequence, the system hangs when resuming the VPU due to the
> power domain dependency.
>
> To ensure the proper suspend/resume order, add a device link betweem
> blk_ctrl and genpd power_dev. It guarantees genpd power_dev is suspended
> after and resumed before blk-ctrl.

Before discussing $subject patch, would you mind explaining to me why
imx8m-blk-ctrl needs to use the ->suspend() callback at all?

Looking closer at that code (imx8m_blk_ctrl_suspend()), it calls
pm_runtime_get_sync() for devices to power on "everything". Why isn't
that managed by the consumer drivers (on a case by case basis) that
are managing the devices that are attached to the genpds instead?

Kind regards
Uffe

>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/all/fccbb040330a706a4f7b34875db1d896a0bf81c8.camel@xxxxxxxxx/
> Link: https://lore.kernel.org/all/20240409085802.290439-1-ivitro@xxxxxxxxx/
> Fixes: 2684ac05a8c4 ("soc: imx: add i.MX8M blk-ctrl driver")
> Suggested-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> Signed-off-by: Vitor Soares <vitor.soares@xxxxxxxxxxx>
> ---
>
> This is a new patch, but is a follow-up of:
> https://lore.kernel.org/all/20240409085802.290439-1-ivitro@xxxxxxxxx/
>
> As suggested by Lucas, we are addressing this PM issue in the imx8m-blk-ctrl
> driver instead of in the imx8mm.dtsi.
>
>  drivers/pmdomain/imx/imx8m-blk-ctrl.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/drivers/pmdomain/imx/imx8m-blk-ctrl.c b/drivers/pmdomain/imx/imx8m-blk-ctrl.c
> index ca942d7929c2..cd0d2296080d 100644
> --- a/drivers/pmdomain/imx/imx8m-blk-ctrl.c
> +++ b/drivers/pmdomain/imx/imx8m-blk-ctrl.c
> @@ -283,6 +283,20 @@ static int imx8m_blk_ctrl_probe(struct platform_device *pdev)
>                         goto cleanup_pds;
>                 }
>
> +               /*
> +                * Enforce suspend/resume ordering by making genpd power_dev a
> +                * provider of blk-ctrl. Genpd power_dev is suspended after and
> +                * resumed before blk-ctrl.
> +                */
> +               if (!device_link_add(dev, domain->power_dev, DL_FLAG_STATELESS)) {
> +                       ret = -EINVAL;
> +                       dev_err_probe(dev, ret,
> +                                     "failed to link to %s\n", data->name);
> +                       pm_genpd_remove(&domain->genpd);
> +                       dev_pm_domain_detach(domain->power_dev, true);
> +                       goto cleanup_pds;
> +               }
> +
>                 /*
>                  * We use runtime PM to trigger power on/off of the upstream GPC
>                  * domain, as a strict hierarchical parent/child power domain
> @@ -324,6 +338,7 @@ static int imx8m_blk_ctrl_probe(struct platform_device *pdev)
>         of_genpd_del_provider(dev->of_node);
>  cleanup_pds:
>         for (i--; i >= 0; i--) {
> +               device_link_remove(dev, bc->domains[i].power_dev);
>                 pm_genpd_remove(&bc->domains[i].genpd);
>                 dev_pm_domain_detach(bc->domains[i].power_dev, true);
>         }
> @@ -343,6 +358,7 @@ static void imx8m_blk_ctrl_remove(struct platform_device *pdev)
>         for (i = 0; bc->onecell_data.num_domains; i++) {
>                 struct imx8m_blk_ctrl_domain *domain = &bc->domains[i];
>
> +               device_link_remove(&pdev->dev, domain->power_dev);
>                 pm_genpd_remove(&domain->genpd);
>                 dev_pm_domain_detach(domain->power_dev, true);
>         }
> --
> 2.34.1
>