Commit de5e73dc authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Alex Deucher
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drm/amd/display: Simplify the per-CPU usage. 



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: default avatarHarry Wentland <harry.wentland@amd.com>
Reviewed-by: default avatarRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarHamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 9c77dcf6

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

+20 −30
Original line number Diff line number Diff line
@@ -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();

}