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drm/amd/display: Simplify the per-CPU usage.

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The fpu_recursion_depth counter is used to ensure that dc_fpu_begin()
can be invoked multiple times while the FPU-disable function itself is
only invoked once. Also the counter part (dc_fpu_end()) is ballanced
properly.

Instead of using the get_cpu_ptr() dance around the inc it is simpler to
increment the per-CPU variable directly. Also the per-CPU variable has
to be incremented and decremented on the same CPU. This is ensured by
the inner-part which disables preemption. This is kind of not obvious,
works and the preempt-counter is touched a few times for no reason.

Disable preemption before incrementing fpu_recursion_depth for the first
time. Keep preemption disabled until dc_fpu_end() where the counter is
decremented making it obvious that the preemption has to stay disabled
while the counter is non-zero.
Use simple inc/dec functions.
Remove the nested preempt_disable/enable functions which are now not
needed.

Acked-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Sebastian Andrzej Siewior
2023-09-21 16:15:13 +02:00
committed by Alex Deucher
parent 9c77dcf6a5
commit de5e73dc6b
1 changed files with 20 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
View File

@@ -60,11 +60,9 @@ static DEFINE_PER_CPU(int, fpu_recursion_depth);
*/
inline void dc_assert_fp_enabled(void)
{
int *pcpu, depth = 0;
int depth;
pcpu = get_cpu_ptr(&fpu_recursion_depth);
depth = *pcpu;
put_cpu_ptr(&fpu_recursion_depth);
depth = __this_cpu_read(fpu_recursion_depth);
ASSERT(depth >= 1);
}
@@ -84,32 +82,27 @@ inline void dc_assert_fp_enabled(void)
*/
void dc_fpu_begin(const char *function_name, const int line)
{
int *pcpu;
int depth;
pcpu = get_cpu_ptr(&fpu_recursion_depth);
*pcpu += 1;
preempt_disable();
depth = __this_cpu_inc_return(fpu_recursion_depth);
if (*pcpu == 1) {
if (depth == 1) {
#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
kernel_fpu_begin();
#elif defined(CONFIG_PPC64)
if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
preempt_disable();
if (cpu_has_feature(CPU_FTR_VSX_COMP))
enable_kernel_vsx();
} else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
preempt_disable();
else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
enable_kernel_altivec();
} else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
preempt_disable();
else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
enable_kernel_fp();
}
#elif defined(CONFIG_ARM64)
kernel_neon_begin();
#endif
}
TRACE_DCN_FPU(true, function_name, line, *pcpu);
put_cpu_ptr(&fpu_recursion_depth);
TRACE_DCN_FPU(true, function_name, line, depth);
}
/**
@@ -124,29 +117,26 @@ void dc_fpu_begin(const char *function_name, const int line)
*/
void dc_fpu_end(const char *function_name, const int line)
{
int *pcpu;
int depth;
pcpu = get_cpu_ptr(&fpu_recursion_depth);
*pcpu -= 1;
if (*pcpu <= 0) {
depth = __this_cpu_dec_return(fpu_recursion_depth);
if (depth == 0) {
#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
kernel_fpu_end();
#elif defined(CONFIG_PPC64)
if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
if (cpu_has_feature(CPU_FTR_VSX_COMP))
disable_kernel_vsx();
preempt_enable();
} else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
disable_kernel_altivec();
preempt_enable();
} else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
disable_kernel_fp();
preempt_enable();
}
#elif defined(CONFIG_ARM64)
kernel_neon_end();
#endif
} else {
WARN_ON_ONCE(depth < 0);
}
TRACE_DCN_FPU(false, function_name, line, *pcpu);
put_cpu_ptr(&fpu_recursion_depth);
TRACE_DCN_FPU(false, function_name, line, depth);
preempt_enable();
}