[Patch v2 0/2] Fix hang due to CPU BW request as BPMP suspended

[Sumit Gupta <sumitg@nvidia.com>]

This patch set fixes hang during system resume which started coming
after adding Memory Interconnect and OPP support to the Tegra194 CPUFREQ
in below change:
 f41e1442ac5b ("cpufreq: tegra194: add OPP support and set bandwidth").

Tegra194 CPUFREQ driver uses 'CPUFREQ_NEED_INITIAL_FREQ_CHECK' flag
which causes a CPU frequency set request from the 'cpuhp_cpufreq_online'
hotplug notifier during resume. The CPU frequency set call also triggers
a DRAM bandwidth set request but the BPMP driver hasn't resumed yet
which results in hang during resume.

Fix this by resetting the BPMP IPC channels inside tegra_bpmp_transfer*()
API if the bandwidth request came from CPU clusters and the BPMP driver
is still suspended.

---
v[1] -> v2:
- add suspend hook instead of reset hook based approach.
- add suspended instead of needs_reset flag in 'struct tegra_bpmp'.
- add flags field to 'struct tegra_bpmp_message'.
- set TEGRA_BPMP_MESSAGE_RESET flag from MC driver for CPU BW request.
- use suspended and flags to reset BPMP IPC early on resume.

Sumit Gupta (1):
  firmware: tegra: add suspend hook and reset BPMP IPC early on resume

Thierry Reding (1):
  memory: tegra: set BPMP msg flags to reset IPC channels

 drivers/firmware/tegra/bpmp.c   | 30 ++++++++++++++++++++++++++++++
 drivers/memory/tegra/tegra234.c |  4 ++++
 include/soc/tegra/bpmp.h        |  6 ++++++
 3 files changed, 40 insertions(+)

[1] https://lore.kernel.org/linux-tegra/20230830115829.23977-1-sumitg@nvidia.com/

-- 
2.17.1