drivers/ipm: Add ipm_cavs_host: host/DSP communication on adsp_intel
Intel Audio DSPs have "IPC" interrupt delivery and shared memory
window hardware. The Sound Open Firmware project has historically
used the combination of these to implement a bidirectional
message-passing interface. As it happens, this protocol is an
excellent fit for Zephyr's somewhat geriatric but still useful IPM
interface.
This implements a SOF-protocol-compatible transport that will
hopefully prove a bit more futureproof for non-Intel SOF
architectures. It is a software-only device, built on top of the
underlying SOC APIs for the SRAM windows (in cavs-shim) and IPC
(cavs_ipc).
Note that SOF actually has two protocol variants (ipc3 and ipc4): in
both, the command header (passed as the "id" parameter in IPM) is sent
via the hardware doorbell register. But in ipc4, the second hardware
scratch register is used to transmit the first four bytes of the
command before involving the SRAM window (in ipc3, it's ignored).
Both modes are supported by this driver, set IPM_CAVS_HOST_REGWORD to
choose the "ipc4" variant.
Finally: note that the memory layout for the windows in question is
inherited from SOF, and for compatibility (with both SOF and with the
offsets used by the host!) these can't be changed without major
surgery. They're defined in kconfig, but should be treated as
read-only until we get a chance to rework the way Zephyr does its SRAM
window management (and probably in concert with the host drivers).
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
3 files changed
