This patch series enables the QCOM SCM driver to support firmware (FW) versions that expect the high-level OS (HLOS) to be tolerant of SCM call requests not being processed right away and, instead, being placed on a wait-queue in FW and processed accordingly. The problem this feature is fixing is as follows. In a scenario where there is a VM in addition to HLOS (and an underlying hypervisor): 1. HLOS makes an SMC call on core 5 2. The hypervisor scheduling interrupt interrupts this SMC call. 3. The hypervisor schedules the VM on core 5. 4. The VM makes an SMC call on core 5. 5. The SMC call is non-interruptibly stuck on FW spinlock on core 5. 6. HLOS cannot reschedule since core 5 is not responding to Reschedule IPIs. 7. Watchdog timer expires waiting for core 5. This problem is solved by FW returning a new return code SCM_WAITQ_SLEEP to HLOS right away when it is overwhelmed by the VM's SMC call. HLOS then places the call on a wait-queue and wakes it up when it receives an interrupt that signifies "all-clear". There are two new SMC calls also being defined in this design that, together with one new return code, form the handshake protocol between Linux and FW. This design is also backwards-compatible with existing firmware versions that do not support this feature. v4: - Use a single completion as it satisfies all of the current usecases [Bjorn] - Misc. logic/style fixes [Bjorn] - Qualify bindings [Krzysztoff] v3: - Drop allow-multi-call property since HLOS doesn't completely support it yet. - Fixup irq handling so as not to affect SoCs without the interrupt. - Fix warnings reported by kernel test-bot. v2: - Changes made to patches 4 and 5 are listed therein. - Rebased dt-bindings on top of the YAML conversion patch [1]. Older version of the series: [v2] https://patchwork.kernel.org/project/linux-arm-msm/cover/1661898311-30126-1-git-send-email-quic_gurus@xxxxxxxxxxx/ [v1] https://patchwork.kernel.org/project/linux-arm-msm/cover/1656359076-13018-1-git-send-email-quic_gurus@xxxxxxxxxxx/ Guru Das Srinagesh (2): dt-bindings: firmware: qcom-scm: Add optional interrupt firmware: qcom: scm: Add wait-queue handling logic .../bindings/firmware/qcom,scm.yaml | 6 ++ drivers/firmware/qcom_scm-smc.c | 94 ++++++++++++++-- drivers/firmware/qcom_scm.c | 102 +++++++++++++++++- drivers/firmware/qcom_scm.h | 9 ++ 4 files changed, 203 insertions(+), 8 deletions(-) -- 2.17.1
