soc/tegra: pmc: Fix unsafe generic_handle_irq() call

Currently, when resuming from system suspend on Tegra platforms,
the following warning is observed:

WARNING: CPU: 0 PID: 14459 at kernel/irq/irqdesc.c:666
Call trace:
 handle_irq_desc+0x20/0x58 (P)
 tegra186_pmc_wake_syscore_resume+0xe4/0x15c
 syscore_resume+0x3c/0xb8
 suspend_devices_and_enter+0x510/0x540
 pm_suspend+0x16c/0x1d8

The warning occurs because generic_handle_irq() is being called from
a non-interrupt context which is considered as unsafe.

Fix this warning by deferring generic_handle_irq() call to an IRQ work
which gets executed in hard IRQ context where generic_handle_irq()
can be called safely.

When PREEMPT_RT kernels are used, regular IRQ work (initialized with
init_irq_work) is deferred to run in per-CPU kthreads in preemptible
context rather than hard IRQ context. Hence, use the IRQ_WORK_INIT_HARD
variant so that with PREEMPT_RT kernels, the IRQ work is processed in
hardirq context instead of being deferred to a thread which is required
for calling generic_handle_irq().

On non-PREEMPT_RT kernels, both init_irq_work() and IRQ_WORK_INIT_HARD()
execute in IRQ context, so this change has no functional impact for
standard kernel configurations.

Signed-off-by: Petlozu Pravareshwar <petlozup@nvidia.com>
Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
[treding@nvidia.com: miscellaneous cleanups]
Signed-off-by: Thierry Reding <treding@nvidia.com>

Author: Prathamesh Shete

drivers/soc/tegra/pmc.c

@@ -28,6 +28,7 @@
 #include <linux/iopoll.h>
 #include <linux/irqdomain.h>
 #include <linux/irq.h>
+#include <linux/irq_work.h>
 #include <linux/kernel.h>
 #include <linux/of_address.h>
 #include <linux/of_clk.h>
@@ -468,6 +469,10 @@ struct tegra_pmc {
 	unsigned long *wake_sw_status_map;
 	unsigned long *wake_cntrl_level_map;
 	struct syscore syscore;
+
+	/* Pending wake IRQ processing */
+	struct irq_work wake_work;
+	u32 *wake_status;
 };
 
 static struct tegra_pmc *pmc = &(struct tegra_pmc) {
@@ -1905,6 +1910,50 @@ static int tegra_pmc_parse_dt(struct tegra_pmc *pmc, struct device_node *np)
 	return 0;
 }
 
+/* translate sc7 wake sources back into IRQs to catch edge triggered wakeups */
+static void tegra186_pmc_wake_handler(struct irq_work *work)
+{
+	struct tegra_pmc *pmc = container_of(work, struct tegra_pmc, wake_work);
+	unsigned int i, wake;
+
+	for (i = 0; i < pmc->soc->max_wake_vectors; i++) {
+		unsigned long status = pmc->wake_status[i];
+
+		for_each_set_bit(wake, &status, 32) {
+			irq_hw_number_t hwirq = wake + (i * 32);
+			struct irq_desc *desc;
+			unsigned int irq;
+
+			irq = irq_find_mapping(pmc->domain, hwirq);
+			if (!irq) {
+				dev_warn(pmc->dev,
+					 "No IRQ found for WAKE#%lu!\n",
+					 hwirq);
+				continue;
+			}
+
+			dev_dbg(pmc->dev,
+				"Resume caused by WAKE#%lu mapped to IRQ#%u\n",
+				hwirq, irq);
+
+			desc = irq_to_desc(irq);
+			if (!desc) {
+				dev_warn(pmc->dev,
+					 "No descriptor found for IRQ#%u\n",
+					 irq);
+				continue;
+			}
+
+			if (!desc->action || !desc->action->name)
+				continue;
+
+			generic_handle_irq(irq);
+		}
+
+		pmc->wake_status[i] = 0;
+	}
+}
+
 static int tegra_pmc_init(struct tegra_pmc *pmc)
 {
 	if (pmc->soc->max_wake_events > 0) {
@@ -1923,6 +1972,18 @@ static int tegra_pmc_init(struct tegra_pmc *pmc)
 		pmc->wake_cntrl_level_map = bitmap_zalloc(pmc->soc->max_wake_events, GFP_KERNEL);
 		if (!pmc->wake_cntrl_level_map)
 			return -ENOMEM;
+
+		pmc->wake_status = kcalloc(pmc->soc->max_wake_vectors, sizeof(u32), GFP_KERNEL);
+		if (!pmc->wake_status)
+			return -ENOMEM;
+
+		/*
+		 * Initialize IRQ work for processing wake IRQs. Must use
+		 * HARD_IRQ variant to run in hard IRQ context on PREEMPT_RT
+		 * because we call generic_handle_irq() which requires hard
+		 * IRQ context.
+		 */
+		pmc->wake_work = IRQ_WORK_INIT_HARD(tegra186_pmc_wake_handler);
 	}
 
 	if (pmc->soc->init)
@@ -3129,47 +3190,30 @@ static void wke_clear_wake_status(struct tegra_pmc *pmc)
 	}
 }
 
-/* translate sc7 wake sources back into IRQs to catch edge triggered wakeups */
-static void tegra186_pmc_process_wake_events(struct tegra_pmc *pmc, unsigned int index,
-					     unsigned long status)
-{
-	unsigned int wake;
-
-	dev_dbg(pmc->dev, "Wake[%d:%d]  status=%#lx\n", (index * 32) + 31, index * 32, status);
-
-	for_each_set_bit(wake, &status, 32) {
-		irq_hw_number_t hwirq = wake + 32 * index;
-		struct irq_desc *desc;
-		unsigned int irq;
-
-		irq = irq_find_mapping(pmc->domain, hwirq);
-
-		desc = irq_to_desc(irq);
-		if (!desc || !desc->action || !desc->action->name) {
-			dev_dbg(pmc->dev, "Resume caused by WAKE%ld, IRQ %d\n", hwirq, irq);
-			continue;
-		}
-
-		dev_dbg(pmc->dev, "Resume caused by WAKE%ld, %s\n", hwirq, desc->action->name);
-		generic_handle_irq(irq);
-	}
-}
-
 static void tegra186_pmc_wake_syscore_resume(void *data)
 {
-	u32 status, mask;
 	unsigned int i;
+	u32 mask;
 
 	for (i = 0; i < pmc->soc->max_wake_vectors; i++) {
 		mask = readl(pmc->wake + WAKE_AOWAKE_TIER2_ROUTING(i));
-		status = readl(pmc->wake + WAKE_AOWAKE_STATUS_R(i)) & mask;
-
-		tegra186_pmc_process_wake_events(pmc, i, status);
+		pmc->wake_status[i] = readl(pmc->wake + WAKE_AOWAKE_STATUS_R(i)) & mask;
 	}
+
+	/* Schedule IRQ work to process wake IRQs (if any) */
+	irq_work_queue(&pmc->wake_work);
 }
 
 static int tegra186_pmc_wake_syscore_suspend(void *data)
 {
+	unsigned int i;
+
+	/* Check if there are unhandled wake IRQs */
+	for (i = 0; i < pmc->soc->max_wake_vectors; i++)
+		if (pmc->wake_status[i])
+			dev_warn(pmc->dev,
+				 "Unhandled wake IRQs pending vector[%u]: 0x%x\n",
+				 i, pmc->wake_status[i]);
 	wke_read_sw_wake_status(pmc);
 
 	/* flip the wakeup trigger for dual-edge triggered pads