133 lines
4.2 KiB
Diff
133 lines
4.2 KiB
Diff
From 13345b6e1dccf7f0404111eb4081834eaf628563 Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Thu, 21 Sep 2023 16:15:13 +0200
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Subject: [PATCH 011/195] 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()
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can be invoked multiple times while the FPU-disable function itself is
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only invoked once. Also the counter part (dc_fpu_end()) is ballanced
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properly.
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Instead of using the get_cpu_ptr() dance around the inc it is simpler to
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increment the per-CPU variable directly. Also the per-CPU variable has
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to be incremented and decremented on the same CPU. This is ensured by
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the inner-part which disables preemption. This is kind of not obvious,
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works and the preempt-counter is touched a few times for no reason.
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Disable preemption before incrementing fpu_recursion_depth for the first
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time. Keep preemption disabled until dc_fpu_end() where the counter is
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decremented making it obvious that the preemption has to stay disabled
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while the counter is non-zero.
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Use simple inc/dec functions.
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Remove the nested preempt_disable/enable functions which are now not
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needed.
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Link: https://lore.kernel.org/r/20230921141516.520471-3-bigeasy@linutronix.de
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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.../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c | 50 ++++++++-----------
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1 file changed, 20 insertions(+), 30 deletions(-)
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diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
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index 86f4c0e04654..8bd5926b47e0 100644
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--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
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+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
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@@ -60,11 +60,9 @@ static DEFINE_PER_CPU(int, fpu_recursion_depth);
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*/
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inline void dc_assert_fp_enabled(void)
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{
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- int *pcpu, depth = 0;
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+ int depth;
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- pcpu = get_cpu_ptr(&fpu_recursion_depth);
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- depth = *pcpu;
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- put_cpu_ptr(&fpu_recursion_depth);
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+ depth = __this_cpu_read(fpu_recursion_depth);
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ASSERT(depth >= 1);
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}
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@@ -84,32 +82,27 @@ inline void dc_assert_fp_enabled(void)
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*/
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void dc_fpu_begin(const char *function_name, const int line)
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{
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- int *pcpu;
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+ int depth;
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- pcpu = get_cpu_ptr(&fpu_recursion_depth);
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- *pcpu += 1;
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+ preempt_disable();
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+ depth = __this_cpu_inc_return(fpu_recursion_depth);
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- if (*pcpu == 1) {
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+ if (depth == 1) {
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#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
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kernel_fpu_begin();
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#elif defined(CONFIG_PPC64)
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- if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
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- preempt_disable();
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+ if (cpu_has_feature(CPU_FTR_VSX_COMP))
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enable_kernel_vsx();
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- } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
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- preempt_disable();
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+ else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
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enable_kernel_altivec();
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- } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
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- preempt_disable();
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+ else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
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enable_kernel_fp();
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- }
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#elif defined(CONFIG_ARM64)
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kernel_neon_begin();
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#endif
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}
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- TRACE_DCN_FPU(true, function_name, line, *pcpu);
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- put_cpu_ptr(&fpu_recursion_depth);
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+ TRACE_DCN_FPU(true, function_name, line, depth);
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}
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/**
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@@ -124,29 +117,26 @@ void dc_fpu_begin(const char *function_name, const int line)
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*/
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void dc_fpu_end(const char *function_name, const int line)
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{
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- int *pcpu;
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+ int depth;
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- pcpu = get_cpu_ptr(&fpu_recursion_depth);
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- *pcpu -= 1;
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- if (*pcpu <= 0) {
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+ depth = __this_cpu_dec_return(fpu_recursion_depth);
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+ if (depth == 0) {
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#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
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kernel_fpu_end();
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#elif defined(CONFIG_PPC64)
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- if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
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+ if (cpu_has_feature(CPU_FTR_VSX_COMP))
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disable_kernel_vsx();
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- preempt_enable();
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- } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
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+ else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
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disable_kernel_altivec();
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- preempt_enable();
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- } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
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+ else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
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disable_kernel_fp();
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- preempt_enable();
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- }
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#elif defined(CONFIG_ARM64)
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kernel_neon_end();
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#endif
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+ } else {
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+ WARN_ON_ONCE(depth < 0);
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}
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- TRACE_DCN_FPU(false, function_name, line, *pcpu);
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- put_cpu_ptr(&fpu_recursion_depth);
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+ TRACE_DCN_FPU(false, function_name, line, depth);
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+ preempt_enable();
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}
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--
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2.43.0
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