dram: add a debug option to track bad cold code

It is important not to run in DRAM code, that can be called on hot
paths, i.e. in LL-scheduler context. Add a Kconfig option to catch
such cases and enable it in debug builds.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

Kconfig.sof

@@ -130,6 +130,13 @@ config COLD_STORE_EXECUTE_DRAM
 	  option to enable this feature to save SRAM and to speed up SRAM
 	  copying of performance-critical data and code.
 
+
+config COLD_STORE_EXECUTE_DEBUG
+	bool "Enable checks for cold code on hot paths"
+	help
+	  This enables an assert_can_be_cold() check, which causes an exception
+	  if called in the LL task context and assert() evaluation is enabled.
+
 config FAST_GET
 	bool "Enable simple refcounting DRAM data copier"
 	default n

app/debug_overlay.conf

@@ -15,3 +15,5 @@ CONFIG_DAI_VERBOSE_GLITCH_WARNINGS=y
 # CONFIG_SYS_HEAP_VALIDATE=y
 # CONFIG_SPIN_VALIDATE=y
 # CONFIG_SPIN_LOCK_TIME_LIMIT=50000
+
+CONFIG_COLD_STORE_EXECUTE_DEBUG=y

posix/include/sof/lib/memory.h

@@ -18,4 +18,6 @@
 #define __cold_rodata
 #endif
 
+#define assert_can_be_cold() do {} while (0)
+
 #endif /* __SOF_LIB_MEMORY_H__ */

src/include/sof/schedule/ll_schedule_domain.h

@@ -240,6 +240,7 @@ struct ll_schedule_domain *zephyr_dma_domain_init(struct dma *dma_array,
 						  uint32_t num_dma,
 						  int clk);
 #endif /* CONFIG_DMA_DOMAIN */
+struct ll_schedule_domain *zephyr_ll_domain(void);
 struct ll_schedule_domain *zephyr_domain_init(int clk);
 #define timer_domain_init(timer, clk) zephyr_domain_init(clk)
 #endif

src/schedule/zephyr_domain.c

@@ -6,6 +6,7 @@
 
 #include <rtos/timer.h>
 #include <rtos/alloc.h>
+#include <rtos/symbol.h>
 #include <sof/lib/cpu.h>
 #include <sof/lib/memory.h>
 #include <sof/lib/watchdog.h>
@@ -321,3 +322,16 @@ struct ll_schedule_domain *zephyr_domain_init(int clk)
 
 	return domain;
 }
+
+bool ll_sch_is_current(void)
+{
+	struct zephyr_domain *zephyr_domain = ll_sch_domain_get_pdata(zephyr_ll_domain());
+
+	if (!zephyr_domain)
+		return false;
+
+	struct zephyr_domain_thread *dt = zephyr_domain->domain_thread + cpu_get_id();
+
+	return k_current_get() == &dt->ll_thread;
+}
+EXPORT_SYMBOL(ll_sch_is_current);

src/schedule/zephyr_ll.c

@@ -555,3 +555,10 @@ void scheduler_get_task_info_ll(struct scheduler_props *scheduler_props,
 	scheduler_get_task_info(scheduler_props, data_off_size, &ll_sch->tasks);
 	zephyr_ll_unlock(ll_sch, &flags);
 }
+
+struct ll_schedule_domain *zephyr_ll_domain(void)
+{
+	struct zephyr_ll *ll_sch = scheduler_get_data(SOF_SCHEDULE_LL_TIMER);
+
+	return ll_sch->ll_domain;
+}

xtos/include/sof/lib/memory.h

@@ -18,4 +18,6 @@
 #define __cold_rodata
 #endif
 
+#define assert_can_be_cold() do {} while (0)
+
 #endif /* __SOF_LIB_MEMORY_H__ */

zephyr/include/sof/lib/memory.h

@@ -16,4 +16,21 @@
 #define __cold_rodata
 #endif
 
+#if CONFIG_COLD_STORE_EXECUTE_DEBUG
+#include <rtos/panic.h>
+
+#ifdef __ZEPHYR__
+bool ll_sch_is_current(void);
+#else
+#define ll_sch_is_current() false
+#endif
+
+static inline void assert_can_be_cold(void)
+{
+	assert(!ll_sch_is_current());
+}
+#else
+#define assert_can_be_cold() do {} while (0)
+#endif
+
 #endif /* __SOF_LIB_MEMORY_H__ */