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| /openbmc/linux/drivers/memory/tegra/ |
| H A D | tegra20-emc.c | adbcec88 Thu Mar 19 14:36:47 CDT 2020 Dmitry Osipenko <digetx@gmail.com> memory: tegra20-emc: Poll EMC-CaR handshake instead of waiting for interrupt
The memory clock-rate change could be running on a non-boot CPU, while the
boot CPU handles the EMC interrupt. This introduces an unnecessary latency
since boot CPU should handle the interrupt and then notify the sibling CPU
about clock-rate change completion. In some rare cases boot CPU could be
in uninterruptible state for a significant time (like in a case of KASAN +
NFS root), it could get to the point that completion timeouts before boot
CPU gets a chance to handle interrupt. The solution is to get rid of the
completion and replace it with interrupt-status polling.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
adbcec88 Thu Mar 19 14:36:47 CDT 2020 Dmitry Osipenko <digetx@gmail.com> memory: tegra20-emc: Poll EMC-CaR handshake instead of waiting for interrupt
The memory clock-rate change could be running on a non-boot CPU, while the
boot CPU handles the EMC interrupt. This introduces an unnecessary latency
since boot CPU should handle the interrupt and then notify the sibling CPU
about clock-rate change completion. In some rare cases boot CPU could be
in uninterruptible state for a significant time (like in a case of KASAN +
NFS root), it could get to the point that completion timeouts before boot
CPU gets a chance to handle interrupt. The solution is to get rid of the
completion and replace it with interrupt-status polling.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
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