Commit 0ea7ee82 authored by Rodrigo Siqueira's avatar Rodrigo Siqueira Committed by Alex Deucher

drm/amd/display: Add DC_FP helper to check FPU state

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.

Changes cince V3:
- Rebase

Changes cince V2 (Christian):
- Do not use this_cpu_* between get/put_cpu_ptr().
- In the kernel documentation, better describe restrictions.
- Make dc_assert_fp_enabled trigger the ASSERT message.

Changes since V1:
- Remove fp_enable variables
- Rename dc_is_fp_enabled to dc_assert_fp_enabled
- Replace wrong variable type

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Anson Jacob <Anson.Jacob@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Hersen Wu <hersenxs.wu@amd.com>
Cc: Aric Cyr <aric.cyr@amd.com>
Cc: Jun Lei <jun.lei@amd.com>
Cc: Dmytro Laktyushkin <dmytro.laktyushkin@amd.com>
Cc: Qingqing Zhuo <qingqing.zhuo@amd.com>
Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed-by: default avatarChristian König <christian.koenig@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 2d8471dc
......@@ -46,6 +46,25 @@
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
......
......@@ -27,6 +27,7 @@
#ifndef __DC_FPU_H__
#define __DC_FPU_H__
void dc_assert_fp_enabled(void);
void dc_fpu_begin(const char *function_name, const int line);
void dc_fpu_end(const char *function_name, const int line);
......
......@@ -2357,7 +2357,9 @@ int dcn20_populate_dml_pipes_from_context(
}
/* populate writeback information */
DC_FP_START();
dc->res_pool->funcs->populate_dml_writeback_from_context(dc, res_ctx, pipes);
DC_FP_END();
return pipe_cnt;
}
......
......@@ -43,6 +43,22 @@
* 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,
......@@ -51,6 +67,8 @@ 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];
......
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