[PATCH v4 1/4] media: qcom: camss: Add PM clock support and integrate with runtime PM

[Loic Poulain]

Add optional PM clock support to the CAMSS driver using the PM clock
framework. This allows CAMSS clocks to be registered once and
automatically managed during runtime suspend and resume.

This is especially useful for global CAMSS clocks that are shared across
multiple CAMSS subblocks.

This avoids the need for each subblock to reference and manage the
shared clocks individually. A typical example is the set of clocks in
the top_group, which may be used by CSID, PHY, CCI, and other CAMSS
blocks.

Introduce a small PM clock descriptor table in the CAMSS resources
structure to describe clocks and their optional rates. Initialize
these clocks at probe time and delegate clock ownership to the PM
core.

Hook PM clock handling into the runtime PM callbacks to ensure clocks
are properly suspended and resumed alongside power domains and ICC
paths.

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxxxxxxxx>
---
 drivers/media/platform/qcom/camss/camss.c | 49 +++++++++++++++++++++++++++++++
 drivers/media/platform/qcom/camss/camss.h |  1 +
 2 files changed, 50 insertions(+)

diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
index 2123f6388e3d7eafe669efd6b033e22d8eb5cf79..b541071e97fe02f38aebda1d9b096b930d1cfde5 100644
--- a/drivers/media/platform/qcom/camss/camss.c
+++ b/drivers/media/platform/qcom/camss/camss.c
@@ -18,6 +18,7 @@
 #include <linux/of_graph.h>
 #include <linux/pm_runtime.h>
 #include <linux/pm_domain.h>
+#include <linux/pm_clock.h>
 #include <linux/slab.h>
 #include <linux/videodev2.h>
 
@@ -5346,6 +5347,40 @@ static void camss_genpd_cleanup(struct camss *camss)
 	dev_pm_domain_detach(camss->genpd, true);
 }
 
+/*
+ * camss_init_pm_clks - set up shared CAMSS clocks
+ *
+ * Clocks listed in res->pm_clks are shared across all CAMSS sub-devices
+ * (e.g. top_ahb, axi).
+ */
+static int camss_init_pm_clks(struct camss *camss)
+{
+	struct device *dev = camss->dev;
+	unsigned int i;
+	int ret;
+
+	if (!camss->res->pm_clks[0])
+		return 0;
+
+	if (IS_ENABLED(CONFIG_PM_CLK)) {
+		ret = devm_pm_clk_create(dev);
+		if (ret)
+			return ret;
+	}
+
+	for (i = 0; i < CAMSS_RES_MAX && camss->res->pm_clks[i]; i++) {
+		if (IS_ENABLED(CONFIG_PM_CLK))
+			ret = pm_clk_add(dev, camss->res->pm_clks[i]);
+		else
+			ret = PTR_ERR_OR_ZERO(devm_clk_get_enabled(dev, camss->res->pm_clks[i]));
+		if (ret)
+			return dev_err_probe(dev, ret, "failed to set up pm clock %s\n",
+					     camss->res->pm_clks[i]);
+	}
+
+	return 0;
+}
+
 /*
  * camss_probe - Probe CAMSS platform device
  * @pdev: Pointer to CAMSS platform device
@@ -5434,6 +5469,10 @@ static int camss_probe(struct platform_device *pdev)
 
 	pm_runtime_enable(dev);
 
+	ret = camss_init_pm_clks(camss);
+	if (ret)
+		goto err_v4l2_device_unregister;
+
 	ret = camss_parse_ports(camss);
 	if (ret < 0)
 		goto err_v4l2_device_unregister;
@@ -5775,7 +5814,11 @@ static int __maybe_unused camss_runtime_suspend(struct device *dev)
 			return ret;
 	}
 
+#if IS_ENABLED(CONFIG_PM_CLK)
+	return pm_clk_suspend(dev);
+#else
 	return 0;
+#endif
 }
 
 static int __maybe_unused camss_runtime_resume(struct device *dev)
@@ -5785,6 +5828,12 @@ static int __maybe_unused camss_runtime_resume(struct device *dev)
 	int i;
 	int ret;
 
+#if IS_ENABLED(CONFIG_PM_CLK)
+	ret = pm_clk_resume(dev);
+	if (ret)
+		return ret;
+#endif
+
 	for (i = 0; i < camss->res->icc_path_num; i++) {
 		ret = icc_set_bw(camss->icc_path[i],
 				 icc_res[i].icc_bw_tbl.avg,
diff --git a/drivers/media/platform/qcom/camss/camss.h b/drivers/media/platform/qcom/camss/camss.h
index 93d691c8ac63b2a47dbb234856b627d8911a1851..fe5fe25d5f18d8a3ce35b48077a975f1453c341f 100644
--- a/drivers/media/platform/qcom/camss/camss.h
+++ b/drivers/media/platform/qcom/camss/camss.h
@@ -107,6 +107,7 @@ enum icc_count {
 struct camss_resources {
 	enum camss_version version;
 	const char *pd_name;
+	const char *pm_clks[CAMSS_RES_MAX];
 	const struct camss_subdev_resources *csiphy_res;
 	const struct camss_subdev_resources *tpg_res;
 	const struct camss_subdev_resources *csid_res;

-- 
2.34.1