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c4019198cf
Currently when CPU goes idle, we take a snapshot of PURR via pseries_idle_prolog() which is used at the CPU idle exit to compute the idle PURR cycles via the function pseries_idle_epilog(). Thus, the value of idle PURR cycle thus read before pseries_idle_prolog() and after pseries_idle_epilog() is always correct. However, if we were to read the idle PURR cycles from an interrupt context between pseries_idle_prolog() and pseries_idle_epilog() (this will be done in a future patch), then, the value of the idle PURR thus read will not include the cycles spent in the most recent idle period. Thus, in that interrupt context, we will need access to the snapshot of the PURR before going idle, in order to compute the idle PURR cycles for the latest idle duration. In this patch, we save the snapshot of PURR in pseries_idle_prolog() in a per-cpu variable, instead of on the stack, so that it can be accessed from an interrupt context. Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1586249263-14048-3-git-send-email-ego@linux.vnet.ibm.com
45 lines
1.0 KiB
C
45 lines
1.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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#ifndef _ASM_POWERPC_IDLE_H
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#define _ASM_POWERPC_IDLE_H
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#include <asm/runlatch.h>
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#include <asm/paca.h>
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#ifdef CONFIG_PPC_PSERIES
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DECLARE_PER_CPU(u64, idle_entry_purr_snap);
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static inline void snapshot_purr_idle_entry(void)
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{
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*this_cpu_ptr(&idle_entry_purr_snap) = mfspr(SPRN_PURR);
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}
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static inline void update_idle_purr_accounting(void)
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{
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u64 wait_cycles;
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u64 in_purr = *this_cpu_ptr(&idle_entry_purr_snap);
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wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
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wait_cycles += mfspr(SPRN_PURR) - in_purr;
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get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
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}
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static inline void pseries_idle_prolog(void)
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{
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ppc64_runlatch_off();
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snapshot_purr_idle_entry();
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/*
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* Indicate to the HV that we are idle. Now would be
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* a good time to find other work to dispatch.
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*/
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get_lppaca()->idle = 1;
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}
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static inline void pseries_idle_epilog(void)
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{
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update_idle_purr_accounting();
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get_lppaca()->idle = 0;
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ppc64_runlatch_on();
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}
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#endif /* CONFIG_PPC_PSERIES */
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#endif
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