[PATCH v2 2/2] clk: imx95-blk-ctl: Save/restore registers when RPM routines are called

[Laurentiu Palcu]

When runtime PM is used for clock providers that are part of a power
domain, the power domain supply is cut off during runtime suspend. This
causes all BLK CTL registers belonging to that power domain to reset. To
prevent this, save the state of the registers before entering suspend
and restore them on resume. Additionally, disable the APB clock during
suspend to minimize power consumption.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu at oss.nxp.com>
---
 drivers/clk/imx/clk-imx95-blk-ctl.c | 33 ++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/drivers/clk/imx/clk-imx95-blk-ctl.c b/drivers/clk/imx/clk-imx95-blk-ctl.c
index c72debaf3a60b..56bed44719954 100644
--- a/drivers/clk/imx/clk-imx95-blk-ctl.c
+++ b/drivers/clk/imx/clk-imx95-blk-ctl.c
@@ -453,15 +453,24 @@ static int imx95_bc_runtime_suspend(struct device *dev)
 {
 	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
 
+	bc->clk_reg_restore = readl(bc->base + bc->pdata->clk_reg_offset);
 	clk_disable_unprepare(bc->clk_apb);
+
 	return 0;
 }
 
 static int imx95_bc_runtime_resume(struct device *dev)
 {
 	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
+	int ret;
 
-	return clk_prepare_enable(bc->clk_apb);
+	ret = clk_prepare_enable(bc->clk_apb);
+	if (ret)
+		return ret;
+
+	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
+
+	return 0;
 }
 #endif
 
@@ -469,17 +478,12 @@ static int imx95_bc_runtime_resume(struct device *dev)
 static int imx95_bc_suspend(struct device *dev)
 {
 	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
-	int ret;
 
-	if (bc->pdata->rpm_enabled) {
-		ret = pm_runtime_get_sync(bc->dev);
-		if (ret < 0) {
-			pm_runtime_put_noidle(bc->dev);
-			return ret;
-		}
-	}
+	if (pm_runtime_suspended(dev))
+		return 0;
 
 	bc->clk_reg_restore = readl(bc->base + bc->pdata->clk_reg_offset);
+	clk_disable_unprepare(bc->clk_apb);
 
 	return 0;
 }
@@ -487,11 +491,16 @@ static int imx95_bc_suspend(struct device *dev)
 static int imx95_bc_resume(struct device *dev)
 {
 	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
+	int ret;
 
-	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
+	if (pm_runtime_suspended(dev))
+		return 0;
 
-	if (bc->pdata->rpm_enabled)
-		pm_runtime_put(bc->dev);
+	ret = clk_prepare_enable(bc->clk_apb);
+	if (ret)
+		return ret;
+
+	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
 
 	return 0;
 }
-- 
2.49.0