1 files changed, 89 insertions, 0 deletions
diff --git a/drivers/clk/qcom/apcs-msm8996.c b/drivers/clk/qcom/apcs-msm8996.c
new file mode 100644
index 0000000000..3e91e9e6da
--- /dev/null
+++ b/drivers/clk/qcom/apcs-msm8996.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Qualcomm APCS clock controller driver
+ *
+ * Copyright (c) 2022, Linaro Limited
+ * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
+ */
+
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/clk-provider.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define APCS_AUX_OFFSET	0x50
+
+#define APCS_AUX_DIV_MASK GENMASK(17, 16)
+#define APCS_AUX_DIV_2 0x1
+
+static int qcom_apcs_msm8996_clk_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device *parent = dev->parent;
+	struct regmap *regmap;
+	struct clk_hw *hw;
+	unsigned int val;
+	int ret = -ENODEV;
+
+	regmap = dev_get_regmap(parent, NULL);
+	if (!regmap) {
+		dev_err(dev, "failed to get regmap: %d\n", ret);
+		return ret;
+	}
+
+	regmap_read(regmap, APCS_AUX_OFFSET, &val);
+	regmap_update_bits(regmap, APCS_AUX_OFFSET, APCS_AUX_DIV_MASK,
+			   FIELD_PREP(APCS_AUX_DIV_MASK, APCS_AUX_DIV_2));
+
+	/*
+	 * This clock is used during CPU cluster setup while setting up CPU PLLs.
+	 * Add hardware mandated delay to make sure that the sys_apcs_aux clock
+	 * is stable (after setting the divider) before continuing
+	 * bootstrapping to keep CPUs from ending up in a weird state.
+	 */
+	udelay(5);
+
+	/*
+	 * As this clocks is a parent of the CPU cluster clocks and is actually
+	 * used as a parent during CPU clocks setup, we want for it to register
+	 * as early as possible, without letting fw_devlink to delay probing of
+	 * either of the drivers.
+	 *
+	 * The sys_apcs_aux is a child (divider) of gpll0, but we register it
+	 * as a fixed rate clock instead to ease bootstrapping procedure. By
+	 * doing this we make sure that CPU cluster clocks are able to be setup
+	 * early during the boot process (as it is recommended by Qualcomm).
+	 */
+	hw = devm_clk_hw_register_fixed_rate(dev, "sys_apcs_aux", NULL, 0, 300000000);
+	if (IS_ERR(hw))
+		return PTR_ERR(hw);
+
+	return devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, hw);
+}
+
+static struct platform_driver qcom_apcs_msm8996_clk_driver = {
+	.probe = qcom_apcs_msm8996_clk_probe,
+	.driver = {
+		.name = "qcom-apcs-msm8996-clk",
+	},
+};
+
+/* Register early enough to fix the clock to be used for other cores */
+static int __init qcom_apcs_msm8996_clk_init(void)
+{
+	return platform_driver_register(&qcom_apcs_msm8996_clk_driver);
+}
+postcore_initcall(qcom_apcs_msm8996_clk_init);
+
+static void __exit qcom_apcs_msm8996_clk_exit(void)
+{
+	platform_driver_unregister(&qcom_apcs_msm8996_clk_driver);
+}
+module_exit(qcom_apcs_msm8996_clk_exit);
+
+MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Qualcomm MSM8996 APCS clock driver");