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

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

drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c

+19 −0
Original line number Diff line number Diff line
@@ -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

drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

+2 −0
Original line number Diff line number Diff 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;

}

drivers/gpu/drm/amd/display/dc/dml/dcn2x/dcn2x.c

+18 −0
Original line number Diff line number Diff line
@@ -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];