linux-kernel - [RFC PATCH v2 6/8] clk: scmi: Support atomic enable/disable API

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Message-Id: <20210705171022.25861-7-cristian.marussi@arm.com>
Date:   Mon,  5 Jul 2021 18:10:20 +0100
From:   Cristian Marussi <cristian.marussi@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     sudeep.holla@....com, james.quinlan@...adcom.com,
        Jonathan.Cameron@...wei.com, f.fainelli@...il.com,
        etienne.carriere@...aro.org, vincent.guittot@...aro.org,
        souvik.chakravarty@....com, cristian.marussi@....com
Subject: [RFC PATCH v2 6/8] clk: scmi: Support atomic enable/disable API

Support enable/disable clk_ops instead of prepare/unprepare when the
underlying SCMI transport is configured to support atomic transactions for
synchronous commands.

Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
 drivers/clk/clk-scmi.c | 44 +++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
index 1e357d364ca2..a07117d5e5bd 100644
--- a/drivers/clk/clk-scmi.c
+++ b/drivers/clk/clk-scmi.c
@@ -88,21 +88,42 @@ static void scmi_clk_disable(struct clk_hw *hw)
 	scmi_proto_clk_ops->disable(clk->ph, clk->id);
 }
 
+/*
+ * We can provide enable/disable atomic callbacks only if the underlying SCMI
+ * transport for this SCMI instance is configured to handle synchronous commands
+ * in an atomic manner.
+ *
+ * When no SCMI atomic transport support is available we instead provide the
+ * prepare/unprepare API, as allowed by the clock framework where atomic calls
+ * are not available.
+ *
+ * Note that the provided clk_ops implementations are the same in both cases,
+ * using indeed the same underlying SCMI clock_protocol operations, it's just
+ * that they are assured to act in an atomic manner or not depending on the
+ * actual underlying SCMI transport configuration.
+ *
+ * Two distinct sets of clk_ops are provided since we could have multiple SCMI
+ * instances with different underlying transport quality, so they cannot be
+ * shared.
+ */
 static const struct clk_ops scmi_clk_ops = {
 	.recalc_rate = scmi_clk_recalc_rate,
 	.round_rate = scmi_clk_round_rate,
 	.set_rate = scmi_clk_set_rate,
-	/*
-	 * We can't provide enable/disable callback as we can't perform the same
-	 * in atomic context. Since the clock framework provides standard API
-	 * clk_prepare_enable that helps cases using clk_enable in non-atomic
-	 * context, it should be fine providing prepare/unprepare.
-	 */
 	.prepare = scmi_clk_enable,
 	.unprepare = scmi_clk_disable,
 };
 
-static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk)
+static const struct clk_ops scmi_atomic_clk_ops = {
+	.recalc_rate = scmi_clk_recalc_rate,
+	.round_rate = scmi_clk_round_rate,
+	.set_rate = scmi_clk_set_rate,
+	.enable = scmi_clk_enable,
+	.disable = scmi_clk_disable,
+};
+
+static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk,
+			     const struct clk_ops *scmi_ops)
 {
 	int ret;
 	unsigned long min_rate, max_rate;
@@ -110,7 +131,7 @@ static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk)
 	struct clk_init_data init = {
 		.flags = CLK_GET_RATE_NOCACHE,
 		.num_parents = 0,
-		.ops = &scmi_clk_ops,
+		.ops = scmi_ops,
 		.name = sclk->info->name,
 	};
 
@@ -145,6 +166,7 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 	struct device_node *np = dev->of_node;
 	const struct scmi_handle *handle = sdev->handle;
 	struct scmi_protocol_handle *ph;
+	bool is_atomic;
 
 	if (!handle)
 		return -ENODEV;
@@ -168,6 +190,8 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 	clk_data->num = count;
 	hws = clk_data->hws;
 
+	is_atomic = handle->is_transport_atomic(handle);
+
 	for (idx = 0; idx < count; idx++) {
 		struct scmi_clk *sclk;
 
@@ -184,7 +208,9 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 		sclk->id = idx;
 		sclk->ph = ph;
 
-		err = scmi_clk_ops_init(dev, sclk);
+		err = scmi_clk_ops_init(dev, sclk,
+					is_atomic ? &scmi_atomic_clk_ops :
+					&scmi_clk_ops);
 		if (err) {
 			dev_err(dev, "failed to register clock %d\n", idx);
 			devm_kfree(dev, sclk);
-- 
2.17.1