[PATCH net v2 2/4] net: pcs: xpcs-plat: fix clock lifecycle for !CONFIG_PM builds

[Coia Prant]

With CONFIG_PM disabled, pm_runtime_enable() and the runtime resume path
are compiled out, so the CSR clock is never prepared/enabled. On
platforms that provide a real "csr" clock this makes register access
fail.

Handle this by preparing/enabling the CSR clock manually in the !PM case
and disabling it in the devm cleanup action. The CONFIG_PM path is left
unchanged and still relies on runtime PM to gate the clock.

Use RUNTIME_PM_OPS() and pm_ptr() for the PM ops as well, so that in
!CONFIG_PM builds the runtime callbacks are still referenced and .pm is
NULL rather than pointing at an empty ops structure. This also drops the
__maybe_unused annotations from the callbacks, which were only needed
because SET_RUNTIME_PM_OPS() expands to nothing when CONFIG_PM is
disabled. Both changes are no-ops when CONFIG_PM is enabled.

The CSR clock is optional (devm_clk_get_optional()), so platforms
without a clock keep working in both cases, and clk_prepare_enable()
on a NULL clock is a no-op. Because the !PM case is handled in the
driver, there is no need to select or depend on PM in Kconfig for all
platforms; keep the current Kconfig as-is to preserve compile coverage.

Signed-off-by: Coia Prant <coiaprant@xxxxxxxxx>
---
 drivers/net/pcs/pcs-xpcs-plat.c | 46 ++++++++++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 6 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs-plat.c b/drivers/net/pcs/pcs-xpcs-plat.c
index 11c4239bfd74..c4404500bac6 100644
--- a/drivers/net/pcs/pcs-xpcs-plat.c
+++ b/drivers/net/pcs/pcs-xpcs-plat.c
@@ -275,6 +275,7 @@ static int xpcs_plat_init_res(struct dw_xpcs_plat *pxpcs)
 	return 0;
 }
 
+#ifdef CONFIG_PM
 static void xpcs_plat_exit_clk(void *data)
 {
 	struct dw_xpcs_plat *pxpcs = data;
@@ -304,6 +305,39 @@ static int xpcs_plat_init_clk(struct dw_xpcs_plat *pxpcs)
 
 	return 0;
 }
+#else
+static void xpcs_plat_exit_clk(void *data)
+{
+	struct dw_xpcs_plat *pxpcs = data;
+
+	clk_disable_unprepare(pxpcs->cclk);
+}
+
+static int xpcs_plat_init_clk(struct dw_xpcs_plat *pxpcs)
+{
+	struct device *dev = &pxpcs->pdev->dev;
+	int ret;
+
+	pxpcs->cclk = devm_clk_get_optional(dev, "csr");
+	if (IS_ERR(pxpcs->cclk))
+		return dev_err_probe(dev, PTR_ERR(pxpcs->cclk),
+				     "Failed to get CSR clock\n");
+
+	ret = clk_prepare_enable(pxpcs->cclk);
+	if (ret) {
+		dev_err(dev, "Failed to enable CSR clock: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_add_action_or_reset(dev, xpcs_plat_exit_clk, pxpcs);
+	if (ret) {
+		dev_err(dev, "Failed to register devm for xpcs_plat_exit_clk: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+#endif
 
 static int xpcs_plat_init_bus(struct dw_xpcs_plat *pxpcs)
 {
@@ -408,7 +442,7 @@ static int xpcs_plat_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static int __maybe_unused xpcs_plat_pm_runtime_suspend(struct device *dev)
+static int xpcs_plat_pm_runtime_suspend(struct device *dev)
 {
 	struct dw_xpcs_plat *pxpcs = dev_get_drvdata(dev);
 
@@ -417,7 +451,7 @@ static int __maybe_unused xpcs_plat_pm_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int __maybe_unused xpcs_plat_pm_runtime_resume(struct device *dev)
+static int xpcs_plat_pm_runtime_resume(struct device *dev)
 {
 	struct dw_xpcs_plat *pxpcs = dev_get_drvdata(dev);
 
@@ -425,9 +459,9 @@ static int __maybe_unused xpcs_plat_pm_runtime_resume(struct device *dev)
 }
 
 static const struct dev_pm_ops xpcs_plat_pm_ops = {
-	SET_RUNTIME_PM_OPS(xpcs_plat_pm_runtime_suspend,
-			   xpcs_plat_pm_runtime_resume,
-			   NULL)
+	RUNTIME_PM_OPS(xpcs_plat_pm_runtime_suspend,
+		       xpcs_plat_pm_runtime_resume,
+		       NULL)
 };
 
 DW_XPCS_INFO_DECLARE(xpcs_generic, DW_XPCS_ID_NATIVE, DW_XPCS_PMA_ID_NATIVE);
@@ -456,7 +490,7 @@ static struct platform_driver xpcs_plat_driver = {
 	.probe = xpcs_plat_probe,
 	.driver = {
 		.name = "dwxpcs",
-		.pm = &xpcs_plat_pm_ops,
+		.pm = pm_ptr(&xpcs_plat_pm_ops),
 		.of_match_table = xpcs_of_ids,
 	},
 };
-- 
2.47.3