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

[Vitor Soares]

From: Vitor Soares <vitor.soares at toradex.com>

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.

Cc: <stable at vger.kernel.org>
Closes: https://lore.kernel.org/all/fccbb040330a706a4f7b34875db1d896a0bf81c8.camel@gmail.com/
Link: https://lore.kernel.org/all/20240409085802.290439-1-ivitro@gmail.com/
Fixes: 2684ac05a8c4 ("soc: imx: add i.MX8M blk-ctrl driver")
Suggested-by: Lucas Stach <l.stach at pengutronix.de>
Signed-off-by: Vitor Soares <vitor.soares at toradex.com>
---

This is a new patch, but is a follow-up of:
https://lore.kernel.org/all/20240409085802.290439-1-ivitro@gmail.com/

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