[PATCH 3/7] clk: samsung: Implement PM SMC calls for ARM64 Exynos SoCs

[Sam Protsenko <semen.protsenko@linaro.org>]

Exynos850 requires extra TZPC handling to keep CMU registers non-secure
(accessible from the kernel) after PM resume. It's done using a specific
SMC call to the EL3 monitor. Implement corresponding SMC calls in
suspend and resume functions. Perform those calls when the parent (bus)
clock is running to avoid SMC freezes. The "samsung,tzpc" property is
used to specify the TZPC register address for those calls (for each
particular domain). If that property is not provided, SMC calls won't be
performed, thus keeping the compatibility with CMUs and platforms where
that SMC functionality is not needed.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
---
 drivers/clk/samsung/clk-exynos-arm64.c | 39 ++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/samsung/clk-exynos-arm64.c b/drivers/clk/samsung/clk-exynos-arm64.c
index 7d8937caf22a..57e9bee7ec4d 100644
--- a/drivers/clk/samsung/clk-exynos-arm64.c
+++ b/drivers/clk/samsung/clk-exynos-arm64.c
@@ -8,6 +8,8 @@
  * This file contains shared functions used by some arm64 Exynos SoCs,
  * such as Exynos7885 or Exynos850 to register and init CMUs.
  */
+
+#include <linux/arm-smccc.h>
 #include <linux/clk.h>
 #include <linux/of_address.h>
 #include <linux/of_device.h>
@@ -24,6 +26,12 @@
 #define GATE_OFF_START		0x2000
 #define GATE_OFF_END		0x2fff
 
+/* Power control SMC command and its parameters */
+#define SMC_CMD_PREPARE_PD_ONOFF		0x82000410
+#define EXYNOS_PD_RUNTIME_PM			2
+#define EXYNOS_GET_IN_PD_DOWN			0
+#define EXYNOS_WAKEUP_PD_DOWN			1
+
 struct exynos_arm64_cmu_data {
 	struct samsung_clk_reg_dump *clk_save;
 	unsigned int nr_clk_save;
@@ -34,6 +42,7 @@ struct exynos_arm64_cmu_data {
 	struct clk **pclks;
 	int nr_pclks;
 
+	unsigned int tzpc_addr;			/* address for PM SMC calls */
 	struct samsung_clk_provider *ctx;
 };
 
@@ -149,6 +158,22 @@ static int __init exynos_arm64_cmu_prepare_pm(struct device *dev,
 	return 0;
 }
 
+static int exynos_arm64_pm_smc(struct device *dev, bool on)
+{
+	struct exynos_arm64_cmu_data *data = dev_get_drvdata(dev);
+	struct arm_smccc_res res;
+	unsigned int pm_arg;
+
+	if (!data->tzpc_addr)
+		return 0;
+
+	pm_arg = on ? EXYNOS_WAKEUP_PD_DOWN : EXYNOS_GET_IN_PD_DOWN;
+	arm_smccc_smc(SMC_CMD_PREPARE_PD_ONOFF, pm_arg, data->tzpc_addr,
+		      EXYNOS_PD_RUNTIME_PM, 0, 0, 0, 0, &res);
+
+	return res.a0;
+}
+
 /**
  * exynos_arm64_register_cmu - Register specified Exynos CMU domain
  * @dev:	Device object; may be NULL if this function is not being
@@ -207,6 +232,8 @@ int __init exynos_arm64_register_cmu_pm(struct platform_device *pdev,
 	if (!data)
 		return -ENOMEM;
 
+	of_property_read_u32(np, "samsung,tzpc", (u32 *)&data->tzpc_addr);
+
 	platform_set_drvdata(pdev, data);
 
 	ret = exynos_arm64_cmu_prepare_pm(dev, cmu);
@@ -251,7 +278,7 @@ int __init exynos_arm64_register_cmu_pm(struct platform_device *pdev,
 int exynos_arm64_cmu_suspend(struct device *dev)
 {
 	struct exynos_arm64_cmu_data *data = dev_get_drvdata(dev);
-	int i;
+	int i, ret;
 
 	samsung_clk_save(data->ctx->reg_base, data->clk_save,
 			 data->nr_clk_save);
@@ -263,6 +290,10 @@ int exynos_arm64_cmu_suspend(struct device *dev)
 	samsung_clk_restore(data->ctx->reg_base, data->clk_suspend,
 			    data->nr_clk_suspend);
 
+	ret = exynos_arm64_pm_smc(dev, false);
+	if (ret)
+		return ret;
+
 	for (i = 0; i < data->nr_pclks; i++)
 		clk_disable_unprepare(data->pclks[i]);
 
@@ -274,13 +305,17 @@ int exynos_arm64_cmu_suspend(struct device *dev)
 int exynos_arm64_cmu_resume(struct device *dev)
 {
 	struct exynos_arm64_cmu_data *data = dev_get_drvdata(dev);
-	int i;
+	int i, ret;
 
 	clk_prepare_enable(data->clk);
 
 	for (i = 0; i < data->nr_pclks; i++)
 		clk_prepare_enable(data->pclks[i]);
 
+	ret = exynos_arm64_pm_smc(dev, true);
+	if (ret)
+		return ret;
+
 	samsung_clk_restore(data->ctx->reg_base, data->clk_save,
 			    data->nr_clk_save);
 
-- 
2.39.2