soc: samsung: exynos-pmu: enable CPU hotplug support for gs101

Some additional register writes are required when hotplugging CPUs
on gs101, without these the system hangs when hotplugging.

Specifically a CPU_INFORM register needs to be programmed with
a hint value which is used by the EL3 firmware (el3mon) and the
pmu-intr-gen registers need to be programmed.

With this patch applied, and corresponding DT update CPU hotplug
now works as expected. e.g.

echo 0 > /sys/devices/system/cpu/cpu6/online
echo 1 > /sys/devices/system/cpu/cpu6/online

Note: to maintain compatibility with older DTs that didn't specify
pmu-intr-gen phandle only a warning is issued if the syscon can't
be obtained.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Link: https://lore.kernel.org/r/20250506-contrib-pg-cpu-hotplug-suspend2ram-fixes-v1-v4-5-9f64a2657316@linaro.org
[krzk: few blank line and white-space alignment fixes from checkpatch]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Author: petegriffin

drivers/soc/samsung/exynos-pmu.c

@@ -7,6 +7,7 @@
 
 #include <linux/array_size.h>
 #include <linux/arm-smccc.h>
+#include <linux/cpuhotplug.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/mfd/core.h>
@@ -33,6 +34,7 @@ struct exynos_pmu_context {
 	struct device *dev;
 	const struct exynos_pmu_data *pmu_data;
 	struct regmap *pmureg;
+	struct regmap *pmuintrgen;
 };
 
 void __iomem *pmu_base_addr;
@@ -222,7 +224,8 @@ static const struct regmap_config regmap_smccfg = {
 };
 
 static const struct exynos_pmu_data gs101_pmu_data = {
-	.pmu_secure = true
+	.pmu_secure = true,
+	.pmu_cpuhp = true,
 };
 
 /*
@@ -326,6 +329,59 @@ struct regmap *exynos_get_pmu_regmap_by_phandle(struct device_node *np,
 }
 EXPORT_SYMBOL_GPL(exynos_get_pmu_regmap_by_phandle);
 
+/*
+ * CPU_INFORM register hint values which are used by
+ * EL3 firmware (el3mon).
+ */
+#define CPU_INFORM_CLEAR	0
+#define CPU_INFORM_C2		1
+
+static int gs101_cpuhp_pmu_online(unsigned int cpu)
+{
+	unsigned int cpuhint = smp_processor_id();
+	u32 reg, mask;
+
+	/* clear cpu inform hint */
+	regmap_write(pmu_context->pmureg, GS101_CPU_INFORM(cpuhint),
+		     CPU_INFORM_CLEAR);
+
+	mask = BIT(cpu);
+
+	regmap_update_bits(pmu_context->pmuintrgen, GS101_GRP2_INTR_BID_ENABLE,
+			   mask, (0 << cpu));
+
+	regmap_read(pmu_context->pmuintrgen, GS101_GRP2_INTR_BID_UPEND, &reg);
+
+	regmap_write(pmu_context->pmuintrgen, GS101_GRP2_INTR_BID_CLEAR,
+		     reg & mask);
+
+	return 0;
+}
+
+static int gs101_cpuhp_pmu_offline(unsigned int cpu)
+{
+	u32 reg, mask;
+	unsigned int cpuhint = smp_processor_id();
+
+	/* set cpu inform hint */
+	regmap_write(pmu_context->pmureg, GS101_CPU_INFORM(cpuhint),
+		     CPU_INFORM_C2);
+
+	mask = BIT(cpu);
+	regmap_update_bits(pmu_context->pmuintrgen, GS101_GRP2_INTR_BID_ENABLE,
+			   mask, BIT(cpu));
+
+	regmap_read(pmu_context->pmuintrgen, GS101_GRP1_INTR_BID_UPEND, &reg);
+	regmap_write(pmu_context->pmuintrgen, GS101_GRP1_INTR_BID_CLEAR,
+		     reg & mask);
+
+	mask = (BIT(cpu + 8));
+	regmap_read(pmu_context->pmuintrgen, GS101_GRP1_INTR_BID_UPEND, &reg);
+	regmap_write(pmu_context->pmuintrgen, GS101_GRP1_INTR_BID_CLEAR,
+		     reg & mask);
+	return 0;
+}
+
 static int exynos_pmu_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -378,6 +434,26 @@ static int exynos_pmu_probe(struct platform_device *pdev)
 	pmu_context->pmureg = regmap;
 	pmu_context->dev = dev;
 
+	if (pmu_context->pmu_data && pmu_context->pmu_data->pmu_cpuhp) {
+		pmu_context->pmuintrgen = syscon_regmap_lookup_by_phandle(dev->of_node,
+							"google,pmu-intr-gen-syscon");
+		if (IS_ERR(pmu_context->pmuintrgen)) {
+			/*
+			 * To maintain support for older DTs that didn't specify syscon phandle
+			 * just issue a warning rather than fail to probe.
+			 */
+			dev_warn(&pdev->dev, "pmu-intr-gen syscon unavailable\n");
+		} else {
+			cpuhp_setup_state(CPUHP_BP_PREPARE_DYN,
+					  "soc/exynos-pmu:prepare",
+					  gs101_cpuhp_pmu_online, NULL);
+
+			cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+					  "soc/exynos-pmu:online",
+					  NULL, gs101_cpuhp_pmu_offline);
+		}
+	}
+
 	if (pmu_context->pmu_data && pmu_context->pmu_data->pmu_init)
 		pmu_context->pmu_data->pmu_init();
 

drivers/soc/samsung/exynos-pmu.h

@@ -22,6 +22,7 @@ struct exynos_pmu_data {
 	const struct exynos_pmu_conf *pmu_config;
 	const struct exynos_pmu_conf *pmu_config_extra;
 	bool pmu_secure;
+	bool pmu_cpuhp;
 
 	void (*pmu_init)(void);
 	void (*powerdown_conf)(enum sys_powerdown);

include/linux/soc/samsung/exynos-regs-pmu.h

@@ -658,9 +658,20 @@
 #define EXYNOS5433_PAD_RETENTION_FSYSGENIO_OPTION		(0x32A8)
 
 /* For Tensor GS101 */
+/* PMU ALIVE */
 #define GS101_SYSIP_DAT0					(0x810)
+#define GS101_CPU0_INFORM					(0x860)
+#define GS101_CPU_INFORM(cpu)	\
+			(GS101_CPU0_INFORM + (cpu*4))
 #define GS101_SYSTEM_CONFIGURATION				(0x3A00)
 #define GS101_PHY_CTRL_USB20					(0x3EB0)
 #define GS101_PHY_CTRL_USBDP					(0x3EB4)
 
+/* PMU INTR GEN */
+#define GS101_GRP1_INTR_BID_UPEND				(0x0108)
+#define GS101_GRP1_INTR_BID_CLEAR				(0x010c)
+#define GS101_GRP2_INTR_BID_ENABLE				(0x0200)
+#define GS101_GRP2_INTR_BID_UPEND				(0x0208)
+#define GS101_GRP2_INTR_BID_CLEAR				(0x020c)
+
 #endif /* __LINUX_SOC_EXYNOS_REGS_PMU_H */