[PATCH RFT 03/20] clk: qcom: smd-rpm: Add support for keepalive votes

[Konrad Dybcio]

Some bus clock should always have a minimum (19.2 MHz) vote cast on
them, otherwise the platform will fall apart, hang and reboot.

Add support for specifying which clocks should be kept alive and
always keep a vote on XO_A to make sure the clock tree doesn't
collapse. This removes the need to keep a maximum vote that was
previously guaranteed by clk_smd_rpm_handoff.

This commit is a combination of existing (not-exactly-upstream) work
by Taniya Das, Shawn Guo and myself.

Co-developed-by: Shawn Guo <shawn.guo@xxxxxxxxxx>
Co-developed-by: Taniya Das <quic_tdas@xxxxxxxxxxx>
Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
---
 drivers/clk/qcom/clk-smd-rpm.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
index cce7daa97c1e..8e017c575361 100644
--- a/drivers/clk/qcom/clk-smd-rpm.c
+++ b/drivers/clk/qcom/clk-smd-rpm.c
@@ -4,6 +4,7 @@
  * Copyright (c) 2014, The Linux Foundation. All rights reserved.
  */
 
+#include <linux/clk.h>
 #include <linux/clk-provider.h>
 #include <linux/err.h>
 #include <linux/export.h>
@@ -178,6 +179,8 @@ struct clk_smd_rpm_req {
 struct rpm_smd_clk_desc {
 	struct clk_smd_rpm **clks;
 	size_t num_clks;
+	struct clk_hw **keepalive_clks;
+	size_t num_keepalive_clks;
 };
 
 static DEFINE_MUTEX(rpm_smd_clk_lock);
@@ -1278,6 +1281,7 @@ static int rpm_smd_clk_probe(struct platform_device *pdev)
 	struct qcom_smd_rpm *rpm;
 	struct clk_smd_rpm **rpm_smd_clks;
 	const struct rpm_smd_clk_desc *desc;
+	struct clk_hw **keepalive_clks;
 
 	rpm = dev_get_drvdata(pdev->dev.parent);
 	if (!rpm) {
@@ -1291,6 +1295,7 @@ static int rpm_smd_clk_probe(struct platform_device *pdev)
 
 	rpm_smd_clks = desc->clks;
 	num_clks = desc->num_clks;
+	keepalive_clks = desc->keepalive_clks;
 
 	for (i = 0; i < num_clks; i++) {
 		if (!rpm_smd_clks[i])
@@ -1321,6 +1326,24 @@ static int rpm_smd_clk_probe(struct platform_device *pdev)
 	if (ret)
 		goto err;
 
+	/* Leave a permanent active vote on clocks that require it. */
+	for (i = 0; i < desc->num_keepalive_clks; i++) {
+		if (WARN_ON(!keepalive_clks[i]))
+			continue;
+
+		ret = clk_prepare_enable(keepalive_clks[i]->clk);
+		if (ret)
+			return ret;
+
+		ret = clk_set_rate(keepalive_clks[i]->clk, 19200000);
+		if (ret)
+			return ret;
+	}
+
+	/* Keep an active vote on CXO in case no other driver votes for it. */
+	if (rpm_smd_clks[RPM_SMD_XO_A_CLK_SRC])
+		return clk_prepare_enable(rpm_smd_clks[RPM_SMD_XO_A_CLK_SRC]->hw.clk);
+
 	return 0;
 err:
 	dev_err(&pdev->dev, "Error registering SMD clock driver (%d)\n", ret);

-- 
2.39.2