static DEFINE_PER_CPU(int, fpu_recursion_depth);
+/**
+ * dc_assert_fp_enabled - Check if FPU protection is enabled
+ *
+ * This function tells if the code is already under FPU protection or not. A
+ * function that works as an API for a set of FPU operations can use this
+ * function for checking if the caller invoked it after DC_FP_START(). For
+ * example, take a look at dcn2x.c file.
+ */
+inline void dc_assert_fp_enabled(void)
+{
+ int *pcpu, depth = 0;
+
+ pcpu = get_cpu_ptr(&fpu_recursion_depth);
+ depth = *pcpu;
+ put_cpu_ptr(&fpu_recursion_depth);
+
+ ASSERT(depth > 1);
+}
+
/**
* dc_fpu_begin - Enables FPU protection
* @function_name: A string containing the function name for debug purposes
* that deals with FP register is contained within this call.
* 3. All function that needs to be accessed outside this file requires a
* public interface that not uses any FPU reference.
+ * 4. Developers **must not** use DC_FP_START/END in this file, but they need
+ * to ensure that the caller invokes it before access any function available
+ * in this file. For this reason, public functions in this file must invoke
+ * dc_assert_fp_enabled();
+ *
+ * Let's expand a little bit more the idea in the code pattern. To fully
+ * isolate FPU operations in a single place, we must avoid situations where
+ * compilers spill FP values to registers due to FP enable in a specific C
+ * file. Note that even if we isolate all FPU functions in a single file and
+ * call its interface from other files, the compiler might enable the use of
+ * FPU before we call DC_FP_START. Nevertheless, it is the programmer's
+ * responsibility to invoke DC_FP_START/END in the correct place. To highlight
+ * situations where developers forgot to use the FP protection before calling
+ * the DC FPU interface functions, we introduce a helper that checks if the
+ * function is invoked under FP protection. If not, it will trigger a kernel
+ * warning.
*/
void dcn20_populate_dml_writeback_from_context(struct dc *dc,
{
int pipe_cnt, i;
+ dc_assert_fp_enabled();
+
for (i = 0, pipe_cnt = 0; i < dc->res_pool->pipe_count; i++) {
struct dc_writeback_info *wb_info = &res_ctx->pipe_ctx[i].stream->writeback_info[0];