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authorRobin Murphy <robin.murphy@arm.com>2023-01-23 18:30:38 +0000
committerWill Deacon <will@kernel.org>2023-01-26 13:55:38 +0000
commita428eb4b99ab80454f06ad256b25e930fe8a4954 (patch)
tree490f7973f2fe1c6f7dfc7dfea9cb00c348374406 /arch/nios2
parent68a63a412d18bd2e2577c8928139f92541afa7a6 (diff)
downloadlinux-a428eb4b99ab80454f06ad256b25e930fe8a4954.tar.bz2
Partially revert "perf/arm-cmn: Optimise DTC counter accesses"
It turns out the optimisation implemented by commit 4f2c3872dde5 is totally broken, since all the places that consume hw->dtcs_used for events other than cycle count are still not expecting it to be sparsely populated, and fail to read all the relevant DTC counters correctly if so. If implemented correctly, the optimisation potentially saves up to 3 register reads per event update, which is reasonably significant for events targeting a single node, but still not worth a massive amount of additional code complexity overall. Getting it right within the current design looks a fair bit more involved than it was ever intended to be, so let's just make a functional revert which restores the old behaviour while still backporting easily. Fixes: 4f2c3872dde5 ("perf/arm-cmn: Optimise DTC counter accesses") Reported-by: Ilkka Koskinen <ilkka@os.amperecomputing.com> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Link: https://lore.kernel.org/r/b41bb4ed7283c3d8400ce5cf5e6ec94915e6750f.1674498637.git.robin.murphy@arm.com Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/nios2')
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