Re: [PATCH v3 3/4] drm/amd/display: Add control mechanism for FPU utilization

Am 20.07.21 um 02:49 schrieb Rodrigo Siqueira:

DC invokes DC_FPU_START/END in multiple parts of the code; this can create a situation where we invoke this FPU operation in a nested way or exit too early. For avoiding this situation, this commit adds a mechanism where dc_fpu_begin/end manages the access to kernel_fpu_begin/end.

Change since V2:

• Christian: Do not use this_cpu_* between get/put_cpu_ptr().

Change since V1:

• Use a better variable names
• Use get_cpu_ptr and put_cpu_ptr to better balance preemption enable

and disable

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 Signed-off-by: Rodrigo Siqueira Rodrigo.Siqueira@amd.com

---

.../amd/display/amdgpu_dm/amdgpu_dm_trace.h | 13 ++++--- .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c | 36 ++++++++++++++++--- drivers/gpu/drm/amd/display/dc/dc_trace.h | 4 +-- 3 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h index 230bb12c405e..fdcaea22b456 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h @@ -638,23 +638,26 @@ TRACE_EVENT(amdgpu_refresh_rate_track, );

TRACE_EVENT(dcn_fpu,

•    TP_PROTO(bool begin, const char *function, const int line),
  

•    TP_ARGS(begin, function, line),
  

•    TP_PROTO(bool begin, const char *function, const int line, const int recursion_depth),
  

•    TP_ARGS(begin, function, line, recursion_depth),
  
   TP_STRUCT__entry(
       __field(bool, begin)
       __field(const char *, function)
       __field(int, line)
  

• 	     __field(int, recursion_depth)
  

  ), TP_fast_assign( __entry->begin = begin; __entry->function = function; __entry->line = line;

• 	   __entry->recursion_depth = recursion_depth;
  

  ),

•    TP_printk("%s()+%d: %s",
  

•    TP_printk("%s: recursion_depth: %d: %s()+%d:",
  

•       __entry->begin ? "begin" : "end",
  

•       __entry->recursion_depth,
   __entry->function,
  

•       __entry->line,
  

•       __entry->begin ? "begin" : "end"
  

•       __entry->line
  

  ) );

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c index d5d156a4517e..d0d3e8a34db5 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c @@ -28,6 +28,19 @@

#include <asm/fpu/api.h>

+/**

• • DOC: DC FPU manipulation overview
• • DC core uses FPU operations in multiple parts of the code, which requires a
• • more specialized way to manage these areas' entrance. To fulfill this
• • requirement, we created some wrapper functions that encapsulate
• • kernel_fpu_begin/end to better fit our need in the display component. In
• • summary, in this file, you can find functions related to FPU operation
• • management.
• */

+static DEFINE_PER_CPU(int, fpu_recursion_depth);

• /**
  • dc_fpu_begin - Enables FPU protection
  • @function_name: A string containing the function name for debug purposes

@@ -43,8 +56,16 @@ */ void dc_fpu_begin(const char *function_name, const int line) {

• TRACE_DCN_FPU(true, function_name, line);
• kernel_fpu_begin();

• int *pcpu;
• pcpu = get_cpu_ptr(&fpu_recursion_depth);
• *pcpu += 1;

This needs:

#if defined(CONFIG_X86)

• if (*pcpu == 1)

• kernel_fpu_begin();
  

#elif defined(CONFIG_PPC64) ....

Should I pick up the patches and help a bit with the non x86 support?

Regards, Christian.

• TRACE_DCN_FPU(true, function_name, line, *pcpu);

• put_cpu_ptr(&fpu_recursion_depth); }

  /**

@@ -59,6 +80,13 @@ void dc_fpu_begin(const char *function_name, const int line) */ void dc_fpu_end(const char *function_name, const int line) {

• TRACE_DCN_FPU(false, function_name, line);
• kernel_fpu_end();

• int *pcpu;
• pcpu = get_cpu_ptr(&fpu_recursion_depth);
• *pcpu -= 1;
• if (*pcpu <= 0)

• kernel_fpu_end();
  

• TRACE_DCN_FPU(false, function_name, line, *pcpu);
• put_cpu_ptr(&fpu_recursion_depth); }

diff --git a/drivers/gpu/drm/amd/display/dc/dc_trace.h b/drivers/gpu/drm/amd/display/dc/dc_trace.h index d598ba697e45..c711797e5c9e 100644 --- a/drivers/gpu/drm/amd/display/dc/dc_trace.h +++ b/drivers/gpu/drm/amd/display/dc/dc_trace.h @@ -38,5 +38,5 @@ #define TRACE_DCN_CLOCK_STATE(dcn_clocks) \ trace_amdgpu_dm_dc_clocks_state(dcn_clocks)

-#define TRACE_DCN_FPU(begin, function, line) \

• trace_dcn_fpu(begin, function, line)

+#define TRACE_DCN_FPU(begin, function, line, ref_count) \

• trace_dcn_fpu(begin, function, line, ref_count)