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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0002-drm-amd-display-Simplify-the-per-CPU-usage.patch | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/debian/patches-rt/0002-drm-amd-display-Simplify-the-per-CPU-usage.patch b/debian/patches-rt/0002-drm-amd-display-Simplify-the-per-CPU-usage.patch new file mode 100644 index 000000000..fd18d53e2 --- /dev/null +++ b/debian/patches-rt/0002-drm-amd-display-Simplify-the-per-CPU-usage.patch @@ -0,0 +1,127 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Thu, 21 Sep 2023 16:15:13 +0200 +Subject: [PATCH 2/5] drm/amd/display: Simplify the per-CPU usage. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz + +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. + +Link: https://lore.kernel.org/r/20230921141516.520471-3-bigeasy@linutronix.de +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c | 50 ++++++++++--------------- + 1 file changed, 20 insertions(+), 30 deletions(-) + +--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c ++++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c +@@ -60,11 +60,9 @@ static DEFINE_PER_CPU(int, fpu_recursion + */ + 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_n + */ + 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(); + } |